A spherical adsorbent produced from a bagasse biochar chitosan assembly for selective adsorption of platinum-group metals from wastewater

This study addresses the challenge of platinum-group metal scarcity by exploring the adsorption of these metals from industrial wastewater. An inexpensive adsorbent with selective platinum-group metal adsorption capacity, named chitosan/citric acid@diatomaceous earth-sugarcane bagasse (CTS/CA@DE-SBS), was newly synthesized. The material features a double coating of chitosan and diatomite on bagasse biochar, and it exhibits an excellent adsorption performance for platinum-group metals due to the synergistic effects of the biochar and chitosan-diatomaceous earth intercross-linked coatings. CTS/CA@DE-SBS achieved an 81 % adsorption efficiency and a static saturated adsorption capacity of 217 mg/g for Pt (IV) in water. Notably, the material exhibited selective adsorption properties for platinum-group metals dissolved in diverse aqueous solutions. The potential for the secondary recovery of platinum-group metals in complex aqueous bodies further underscores the significance of this adsorbent. In conclusion, this research introduces a promising solution for platinum-group metal shortages, offering a cost-effective and selective adsorbent with potential applications in the secondary recovery of these metals from industrial wastewater.

Comprehensive enhancement of flame retardant starch/cellulose/diatomite composite foams via metal-organic coordination

In recent years, considerable attention has been given to the utilization of biomass for producing bio-based foams, such as starch-based foams. Despite their renewability and widespread availability, these foams still present certain drawbacks regarding their poor mechanical properties and flammability. To tackle these concerns, a metal ion cross-linking strategy was employed by incorporating calcium ions (Ca2+) solution into foamed starch/cellulose slurry. Followed by ambient drying, starch/cellulose composite foam was successfully fabricated with a remarkable enhancement in various properties. Specifically, compared to the control sample, the compressive strength and modulus increased by 26.2 % and 123.0 %, respectively. Additionally, the Ca2+ cross-linked starch/cellulose composite foam exhibited excellent heat resistance, water stability, and flame retardancy. The limiting oxygen index (LOI) reached 52 %, with a vertical combustion rating of V-0. Along with the addition of 2 phr diatomite, it demonstrated a significant enhancement on flame retardancy with a LOI of 65 %, although the apparent density of the composite foam was not low enough. This study indicated a green and simple method to obtain starch-based composite foams with enhanced comprehensive properties including thermal, water stability, mechanical, and flame retardancy, expanding their potential applications in areas such as building materials and rigid packaging.

Modified Diatomaceous Earth in Heparin Recovery from Porcine Intestinal Mucosa

Heparin, a highly sulfated glycosaminoglycan, is a naturally occurring anticoagulant that plays a vital role in various physiological processes. The remarkable structural complexity of heparin, consisting of repeating disaccharide units, makes it a crucial molecule for the development of commercial drugs in the pharmaceutical industry. Over the past few decades, significant progress has been made in the development of cost-effective adsorbents specifically designed for the adsorption of heparin from porcine intestinal mucosa. This advancement has been driven by the need for efficient and scalable methods to extract heparin from natural sources. In this study, we investigated the use of cationic ammonium-functionalized diatomaceous earth, featuring enhanced porosity, larger surface area, and higher thermal stability, to maximize the isolated heparin recovery. Our results showed that the higher cationic density and less bulky quaternary modified diatomaceous earth (QDADE) could adsorb up to 16.3 mg·g-1 (31%) of heparin from the real mucosa samples. Additionally, we explored the conditions of the adsorbent surface for recovery of the heparin molecule and optimized various factors, such as temperature and pH, to optimize the heparin uptake. This is the introductory account of the implementation of modified diatomaceous earth with quaternary amines for heparin capture.

The catalytic aerial oxidation of As(III) in alkaline solution by Mn-loaded diatomite

The oxidization of As(III) to As(V) is necessary for both the detoxification of arsenic and the removal of arsenic by solidification. In order to achieve high efficiency and low cost As(III) oxidation, a novel process of catalytic aerial oxidation of As(III) is proposed, using air as oxidant and Mn-loaded diatomite as a catalyst. Through systematic characterization of the reaction products, the catalytic oxidation reaction law of Mn-loaded diatomite for As(III) was found out, and its reaction mechanism was revealed. Results show that Mn-loaded diatomite achieved a good catalytic effect for aerial oxidation of As(III) and maintained high performance over multiple cycles of reuse, which was directly related to the structure of diatomite and the behavior of manganese. Under the conditions of a catalyst concentration of 20 g/L, an air flow rate of 0.3 m³/h, a reaction temperature of 50 °C and an initial pH of 12.6, 96.04% As(III) oxidation was achieved after 3 h. Furthermore, the efficiency of As(III) oxidation did not change significantly after ten cycles of reuse. XPS analysis of the reaction products confirmed that the surface of the catalyst was rich in Mn(III), Mn(IV) and adsorbed oxygen(O-H), which was the fundamental reason for the excellent performance of Mn-loaded diatomite in the catalytic oxidation of As(III).

Diatomaceous Earth for Arthropod Pest Control: Back to the Future

Nowadays, we are tackling various issues related to the overuse of synthetic insecticides. Growing concerns about biodiversity, animal and human welfare, and food security are pushing agriculture toward a more sustainable approach, and research is moving in this direction, looking for environmentally friendly alternatives to be adopted in Integrated Pest Management (IPM) protocols. In this regard, inert dusts, especially diatomaceous earths (DEs), hold a significant promise to prevent and control a wide range of arthropod pests. DEs are a type of naturally occurring soft siliceous sedimentary rock, consisting of the fossilized exoskeleton of unicellular algae, which are called diatoms. Mainly adopted for the control of stored product pests, DEs have found also their use against some household insects living in a dry environment, such as bed bugs, or insects of agricultural interest. In this article, we reported a comprehensive review of the use of DEs against different arthropod pest taxa, such as Acarina, Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Ixodida, Lepidoptera, when applied either alone or in combination with other techniques. The mechanisms of action of DEs, their real-world applications, and challenges related to their adoption in IPM programs are critically reported.

Design of Gelatin-Capped Plasmonic-Diatomite Nanoparticles with Enhanced Galunisertib Loading Capacity for Drug Delivery Applications

Inorganic diatomite nanoparticles (DNPs) have gained increasing interest as drug delivery systems due to their porous structure, long half-life, thermal and chemical stability. Gold nanoparticles (AuNPs) provide DNPs with intriguing optical features that can be engineered and optimized for sensing and drug delivery applications. In this work, we combine DNPs with gelatin stabilized AuNPs for the development of an optical platform for Galunisertib delivery. To improve the DNP loading capacity, the hybrid platform is capped with gelatin shells of increasing thicknesses. Here, for the first time, full optical modeling of the hybrid system is proposed to monitor both the gelatin generation, degradation, and consequent Galunisertib release by simple spectroscopic measurements. Indeed, the shell thickness is optically estimated as a function of the polymer concentration by exploiting the localized surface plasmon resonance shifts of AuNPs. We simultaneously prove the enhancement of the drug loading capacity of DNPs and that the theoretical modeling represents an efficient predictive tool to design polymer-coated nanocarriers.

Immobilization of recombinant Escherichia coli cells expressing glucose isomerase using modified diatomite as a carrier for effective production of high fructose corn syrup in packed bed reactor

To improve the operational stability of glucose isomerase in E. coli TEGI-W139F/V186T, the immobilized cells were prepared with modified diatomite as a carrier and 74.1% activity of free cells was recovered after immobilization. Results showed that the immobilized cells still retained 86.2% of the initial transformational activity after intermittent reused 40 cycles and the yield of D-fructose reached above 42% yield at 60 °C. Moreover, the immobilized cells were employed in the continuous production of High Fructose Corn Syrup (HFCS) in a recirculating packed bed reactor for 603 h at a constant flow rate. It showed that the immobilized cells exhibited good operational stability and the yield of D-fructose retained above 42% within 603 h. The space-time yield of high fructose corn syrup reached 3.84 kg L^-1 day^-1. The investigation provided an efficient immobilization method for recombinant cells expressing glucose isomerase with higher stability, and the immobilized cells are a promising biocatalyst for HFCS production.

Enhancing Chromium (VI) removal from synthetic and real tannery effluents by using diatomite-embedded nanopyroxene

A commercial filter aid material of Diatomite was modified via loading it with a low mass fraction of polyethylenimine-functionalized pyroxene nanoparticles (PEI-PNs) to enhance its adsorption activities. The modified Diatomite was then used for Cr(VI) removal from dichromate solution and from real tannery wastewater. For the synthetic wastewater, batch adsorption experiments were first performed at various pH and Cr(VI) initial concentrations. Then, the obtained kinetic parameters were used to investigate the continuous adsorption inside the fixed-bed column. The continuous removal of the Cr(VI) was performed inside a fixed-bed column under various influent flow rates, Cr(VI) initial concentrations, and bed-heights. In the column experiments, high adsorption of Cr(VI) was observed at low flow rates, high bed heights, and low influent initial concentrations. A dimensionless form of the advection-axial dispersion model, featuring Peclet number as a fitting parameter, was then used to study the breakthrough behavior under various dynamic parameters. Afterward, the modified Diatomite was used to remediate well characterized real tannery wastewater. For the treatment of the tannery wastewater, our modified filter aid, compared with the non-modified one, showed an outstanding performance and a higher removal efficiency.

Clay Composites for Thermal Energy Storage: A Review

The development of novel materials and approaches for effective energy consumption and the employment of renewable energy sources is one of the current trends in modern material science. With this respect, the number of researches is focused on the effective harvesting and storage of solar energy for various applications. Phase change materials (PCMs) are known to be able to store thermal energy of the sunlight due to adsorption and release of latent heat through reversible phase transitions. Therefore, PCMs are promising as functional additives to construction materials and paints for advanced thermoregulation in building and industry. However, bare PCMs have limited practical applications. Organic PCMs like paraffins suffer from material leakage when undergoing in a liquid state while inorganic ones like salt hydrates lack long-term stability after multiple phase transitions. To avoid this, the loading of PCMs in porous matrices are intensively studied along with the thermal properties of the resulted composites. The loading of PCMs in microcontainers of natural porous or layered clay materials appears as a simple and cost-effective method of encapsulation significantly improving the shape and cyclic stability of PCMs. Additionally, the inclusion of functional clay containers into construction materials allows for improving their mechanical and flame-retardant properties. This article summarizes the recent progress in the preparation of composites based on PCM-loaded clay microcontainers along with their future perspectives as functional additives in thermo-regulating materials.

MnCeOx/diatomite catalyst for persulfate activation to degrade organic pollutants

Persulfate (PS)-based oxidation technologies are attracting increasing attentions in water treatment due to their high efficiency and stability. In this study, a novel diatomite supported MnCeO_x composite (MnCeO_x/diatomite) was prepared and characterized for activation of PS to degrade organic pollutants. Results indicated that diatomite not only dispersed MnCeO_x and increased the specific surface area of catalyst, but also improved the low-valence metal site (Mn²⁺ and Ce³⁺) and reactive oxygen species site (-OH) of MnCeO_x, thus enhancing the activities of MnCeO_x. MnCeO_x/diatomite/PS showed high efficiency for multiple dyes and pharmaceutical pollutants. Constant rate (k) of MnCeO_x/diatomite (k_{MnCeOx/diatomite}) was three times higher than the sum of constant rate of MnCeO_x (k_MnCeOx) and constant rate of diatomite (k_diatomite). In addition, MnCeO_x/diatomite showed wide pH application (5-9). Cl^- and NO₃^2- had no effect while SO₄^2- and humid acid had slightly negative effects on MnCeO_x/diatomite/PS system. Moreover, MnCeO_x/diatomite showed good reusability and stability. Mechanism analyses indicated that electron transfer of Mn and Ce attributed to the activation of PS and oxygen to produce free radicals. SO₄^-, OH and O₂^- on the surface of catalyst were the main active free radicals to attack pollutants.

Diatoms embedded, self-assembled carriers for dual delivery of chemotherapeutics in cancer cell lines

The concept of dual drug delivery to treat relapsing tumors is a well-studied approach to improve the antitumor efficacies and to reduce the side effects of single drug chemotherapeutic treatments. One of the major issues with dual drug delivery to treat drug resistant tumors is the concentration and ratio dependent antagonistic behavior of two drugs, which may reverse the anticancer efficacies of individual chemotherapeutics and stimulate the growth of tumor cells. In this paper, we address this issue by developing diatomaceous earth embedded core shell materials, which are capable of encapsulating two chemotherapeutic drugs at constant molar ratios, in different compartments of a single drug delivery carrier. The encapsulation of each drug in different compartments of delivery carrier (core of diatoms versus shell of cyclodextrin) then controls the release rate of both drugs in situ, and maintains the optimal molar ratios required for their synergistic outcomes in vitro.

Determination of Urinary Hydroxyl PAHs Using Graphene Oxide@Diatomite Based Solid-Phase Extraction and High-Performance Liquid Chromatography

A diatomite supported graphene oxide composite (GO@Dt–NH₂) was fabricated and explored as a solid-phase extraction adsorbent coupled with high performance liquid chromatography to determine the trace hydroxyl polycyclic aromatic hydrocarbons (2-hydroxy-naphthalene, 2-hydroxy-fluorene, 1-hydroxy-phenanthrene, and 1-hydroxy-pyrene) in urine samples. The fabricated composites were characterized by X-ray powder diffractometry and scanning electron microscopy. GO@Dt–NH₂ offered enhanced adsorption affinity towards the analytes compared with the bare diatomite. The amount of graphene oxide and the factors affecting solid-phase extraction were investigated in detail. Under the optimized conditions, the method gave good linearity (0.30–200 ng/mL) and a low detection limit (0.10–0.15 ng/mL) for the hydroxyl polycyclic aromatic hydrocarbons. The average recovery for spiked urine samples with three levels ranged from 90.6% to 100%. The intra-day and inter-day relative standard deviations were in the range of 1.8–6.4% and 2.7–11.8%, respectively. Besides, the GO@Dt–NH₂ provided enrichment factors of 18–20 and superior purification ability. The developed method was successfully applied to the determination of hydroxyl polycyclic aromatic hydrocarbons in urine samples from smoking volunteers.

Magnetic diatomite for pesticide removal from aqueous solution via hydrophobic interactions

Pesticides are highly hazardous chemicals for the environment and human health and their use in agriculture is constantly increasing. Although 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane 4,4'-DDT was banned at developed countries, it is still one of the most dangerous of chemical due to accumulation in the environment. It is known that the toxicity of DDT affects some enzyme systems biochemically. The main motivation of this study is to develop an effective adsorbate for the removal DDT, which was chosen as a model hydrophobic pesticide, out of aqueous systems. For this purpose, the bare diatomite particles were magnetically modified and a hydrophobic ligand attached to enhance its adsorptive and physio-chemical features. Under optimal conditions, a high adsorption capacity, around 120 mg/g with the hydrophobic and magnetic diatomite particles, modification of the diatomite particles reduced average pores diameter whereas surface area and total pore volume increased (around 15-folds). After five consecutive adsorption-desorption cycles, no significant decrease in adsorption capability was observed. The adsorption isotherms (Langmuir, Freundlich, and Flory-Huggins) applied to the data indicated that the adsorption process occurred via monolayer adsorption in an entropy-driven manner. The kinetic data also revealed the quick adsorption process without any diffusion limitations. Graphical Abstract.

Tetrahydrocannabinol Sensing in Complex Biofluid with Portable Raman Spectrometer Using Diatomaceous SERS Substrates

Using thin-layer chromatography in tandem with surface-enhanced Raman spectroscopy (TLC-SERS) and tetrahydrocannabinol (THC) sensing in complex biological fluids is successfully conducted with a portable Raman spectrometer. Both THC and THC metabolites are detected from the biofluid of marijuana-users as biomarkers for identifying cannabis exposure. In this article, ultra-sensitive SERS substrates based on diatomaceous earth integrated with gold nanoparticles (Au NPs) were employed to detect trace levels of cannabis biomarkers in saliva. Strong characteristic THC and THC metabolite SERS peaks at 1601 and 1681 cm-1 were obtained despite the moderate interference of biological molecules native to saliva. Urine samples were also analyzed, but they required TLC separation of THC from the urine sample to eliminate the strong influence of urea and other organic molecules. TLC separation of THC from the urine was performed by porous microfluidic channel devices using diatomaceous earth as the stationary phase. The experimental results showed clear separation between urea and THC, and strong THC SERS characteristic peaks. Principal component analysis (PCA) was used to analyze the SERS spectra collected from various THC samples. The spectra in the principal component space were well clustered for each sample type and share very similar scores in the main principal component (PC1), which can serve as the benchmark for THC sensing from complex SERS spectra. Therefore, we proved that portable Raman spectrometers can enable an on-site sensing capability using diatomaceous SERS substrates to detect THC in real biological solutions. This portable THC sensing technology will play pivotal roles in forensic analysis, medical diagnosis, and public health.

Visible-light-driven elimination of oxytetracycline and Escherichia coli using magnetic La-doped TiO2/copper ferrite/diatomite composite

The development of powdery photocatalyst has long been studied, yet the low recovery in water is still its bottleneck. In this work, magnetic recyclable lanthanum-doped TiO₂/copper ferrite/diatomite (La-TCD) ternary composite was synthesized via sol-gel method. The physicochemical properties of various hybrid catalysts were characterized and studied, and their photocatalytic properties were evaluated via the decomposition of antibiotic oxytetracycline and disinfection of bacteria Escherichia coli under visible light. The formation of heterojunction between La-doped TiO₂ and copper ferrite hindered the recombination of photo-induced charge carriers and improved the photocatalytic activity. The photodecomposition rate of OTC was accelerated by the high adsorption ability of diatomite, due to the adsorption and decomposition synergistic effect between catalysts and substrate diatomite. The optimal La dopant amount as well as optimal catalyst dosage was determined. The composite could simply be recovered from waterbody via an external magnet, and the repetition tests indicated no obvious decrease of photoactivity. This nanocomposite presented good potential to be applied in environmental remediation process, due to its high photocatalytic efficiency under visible light, as well as its good reusability and stability.

Efficient removal of gaseous formaldehyde by amine-modified diatomite: a combined experimental and density functional theory study

Amine-modified diatomite with remarkable formaldehyde (HCHO) removal efficiency was prepared by grafting 3-aminopropyltrimethoxysilane (APTMS) in this research. The interfacial properties and microstructures of the prepared adsorbents were characterized and analyzed. The HCHO adsorption properties of the amine modified diatomite were also systematically studied, and it has been proven to be effective adsorbent with better adsorption performance than activated carbon for the removal of gaseous HCHO. Furthermore, to better explain the experimental results, we performed density functional theory (DFT) study on the adsorption system and calculated the geometry, energy, and charge parameters based on first principles. Also, the underlying adsorption mechanism was proposed detailedly by combining experimentation with DFT calculation, suggesting that amine modified diatomite can be efficient adsorbent for the elimination of gaseous formaldehyde.

Highly efficient and cost-effective removal of patulin from apple juice by surface engineering of diatomite with sulfur-functionalized graphene oxide

Patulin (PAT) contamination of apple juice leads to a serious food safety issue. Developing an excellent adsorbent to efficiently remove PAT is more desirable. Herein, a cost-effective and efficient adsorbent (GO-SH/diatomite) with abundant active sites was successfully fabricated via surface engineering of diatomite with sulfur-functionalized graphene oxide (GO-SH) nanosheets, which exhibited excellent selective adsorption capacity toward PAT. The adsorption behavior, adsorption mechanism, stability and cytotoxicity were investigated by systematic studies. The adsorption results showed that its maximum adsorption capacity was 10.68 μg/mg. Moreover, attributed to the specific interaction between PAT and thiol group, more than 90% of PAT was removed from apple juice without any juice quality deterioration. Importantly, the risk of food safety issue of apple juice caused by residual GO-SH/diatomite was negligible due to the properties of easy removal and excellent biocompatibility, which guaranteed its potential application in apple juice industry for PAT removal.

Incorporation of Brazilian Diatomite in the Synthesis of An MFI Zeolite

The need for greener procedures is a fact to reduce residues, to decrease industrial costs, and to accomplish the environmental agreements. In an attempt to address this question, we propose the addition of a natural resource, Brazilian diatomite, to an MFI zeolite traditional synthesis. We have characterized the resulting product with different techniques, such as X-ray diffraction, microscopy, and gas sorption, and, afterwards, we evaluate the greenness of the process by the Green Star method. The results were promising: We obtained the desired topology in the form of small crystallites aggregated and a pore diameter of 0.8 nm. In conclusion, the product has the necessary characteristics for an adsorption or catalytic future tests and escalation to industrial production.

La2O3-modified MCM-41 for efficient phosphate removal synthesized using natural diatomite as precursor

In this study, an ordered mesoporous silica modified with lanthanum oxide was synthesized using diatomite as silica source and applied for adsorption of phosphate from aqueous solution. By taking cost-effectiveness for practical application into consideration, the adsorbent with a theoretical La/SiO₂ molar ratio of 0.2 (La_0.2M41) possessed a promising performance. In the batch adsorption tests, the adsorbents with La₂O₃ loading possessed markedly enhanced adsorption capacities. Phosphate uptake by La_0.2M41 was pH-dependent with the highest sorption capacities observed over a pH range of 3.0-6.0. Coexistent anions displayed an adverse effect on phosphate adsorption following the order of CO₃ ^2-  > F^-  > NO₃ ^- > Cl^- > SO₄ ^2-. In the kinetic study, phosphate adsorption onto La_0.2M41 followed the pseudo-second-order equation better than the pseudo-first-order, suggesting chemisorption. The Langmuir isothermal model well described the adsorption isotherm data, showing a maximum adsorption capacity for phosphate of up to 263.16 mg/g at 298 K. In a real treated wastewater effluent with phosphate concentration of 2.5 mg P/L, La_0.2M41 efficiently reduced the phosphate concentration to 28 µg P/L.

Effects of solution chemistry on the attachment of graphene oxide onto clay minerals

With the increase in production and wide application of graphene oxide (GO), colloidal GO particles are expectantly released into soil and groundwater, where a large number of mineral particles exist. In addition, the porewater chemistry (e.g. organic acid, valence of cation) is a neglected but important aspect to comprehensively investigate the fate of GO. The interactions of GO with three ubiquitous clay minerals (i.e., montmorillonite, kaolinite and diatomite) have been systematically investigated through batch experiments across different solution chemistry conditions. In general, the affinity towards GO is in the order of montmorillonite > kaolinite > diatomite under the same experimental conditions. This observation can be explained by the characteristics of different clay minerals, such as surface charge and surface area. The results indicated that increasing the ionic strength or decreasing the pH enhanced the attachment of GO nanoparticles onto clay minerals as a result of electrostatic interactions. With the increase in concentration of Ca2+, more GO particles were attached onto clay mineral particles. This is caused by complexation between the surface oxygen functional groups of both GO nanoparticles and clay minerals. The presence of 0.1 mM tartaric acid significantly inhibited the attachment of GO onto clay minerals. This is possibly linked to the increased negative charges of the organic acids and the competition between organic acids and GO. The interaction energies were also calculated by applying the classical DLVO theory. The results of this study have helped to understand the behavior and fate of GO in subsurface formations.

Factors Affecting Transfer of the Heavy Metals Arsenic, Lead, and Cadmium from Diatomaceous-Earth Filter Aids to Alcoholic Beverages during Laboratory-Scale Filtration

Filtration methods for alcoholic fermented beverages often use filter aids such as diatomaceous earth (DE), which may contain elevated amounts of the heavy metals arsenic (As), lead (Pb), and cadmium (Cd). Here, we evaluated factors affecting transfer of these heavy metals from DE to beer and wine. A laboratory-scale filtration system was used to process unfiltered ale, lager, red wine, and white wine with three types of food-grade DE. Filtrate and DE were analyzed for heavy metals using ICP-MS, in addition to LC-ICP-MS for As-speciation analysis. Use of 2 g/L DE containing 5.4 mg/kg soluble inorganic As (iAs) for filtering beer and wine resulted in significant ( p < 0.05) increases of 11.2-13.7 μg/L iAs in the filtered beverage. There was a significant ( p < 0.05) effect from the DE quantity used in filtration on the transfer of iAs in all beverage types, whereas no alterations were observed for Pb and Cd levels. Methods to wash DE using water, citric acid, or EDTA all significantly ( p < 0.05) reduced iAs concentrations, whereas only EDTA significantly reduced Pb levels. Cd concentrations were not affected by any wash method. These data indicate that specific steps can be taken to limit heavy-metal transfer from DE filter aids to beer and wine.

Extraction of Bioactive Compounds Using Supercritical Carbon Dioxide

Microalgae Dunaliella salina contains useful molecules such as β-carotene and fatty acids (FAs), which are considered high value-added compounds. To extract these molecules, supercritical carbon dioxide was used at different operative conditions. The effects of mechanical pre-treatment (grinding speed at 0–600 rpm; pre-treatment time of 2.5–7.5 min) and operating parameters for extraction, such as biomass loading (2.45 and 7.53 g), pressure (100–550 bars), temperature (50–75 °C) and CO₂ flow rate (7.24 and 14.48 g/min) by varying the extraction times (30–110 min) were evaluated. Results showed that the maximum cumulative recovery (25.48%) of β-carotene was achieved at 400 bars and 65 °C with a CO₂ flow rate of 14.48 g/min, while the highest purity for stage (55.40%) was attained at 550 bars and 65 °C with a CO₂ flow rate of 14.48 g/min. The maximum recovery of FAs, equal to 8.47 mg/g, was achieved at 550 bars and 75 °C with a CO₂ flow rate of 14.48 g/min. Moreover, the lowest biomass loading (2.45 g) and the first extraction cycle (30 min) allowed the maximum extraction of β-carotene and FAs.

Sustainable utilization of a recovered struvite/diatomite compound for lead immobilization in contaminated soil: potential, mechanism, efficiency, and risk assessment

A waste-struvite/diatomite compound (MAP@Dia) recovered from nutrient-rich wastewater treated by MgO-modified diatomite (MgO@Dia) was provided to immobilize lead in aqueous solution and contaminated soil. The mechanism and effectiveness of lead immobilization was investigated, and the pH_stat leaching test and fixed-bed column experiments were carried out to assess the risk of MAP@Dia reuse for lead immobilization. The results showed that MAP@Dia were effective in immobilizing lead in aqueous solution with adsorption capacity of 832.47-946.50 mg/g. The main mechanism of Pb immobilization by MAP@Dia could be contributed by surface complexation and dissolution of struvite followed by precipitation of hydroxypyromorphite Pb₁₀(PO₄)₆(OH)₂. Lead(II) concentration reduced from 269.61 to 78.26 mg/kg, and residual lead(II) increased to 53.14% in contaminated soil when the MAP@Dia application rate was 5%. The increased neutralization capacity (ANC) and lower lead extraction yields in pH_stat leaching test in amended soil suggested 5 times of buffering capacity against potential acidic stresses and delayed triggering of "chemical time bombs." The results of column studies demonstrated that amendment with MAP@Dia could reduce the risk of lead and phosphorus (P) leaching. This study revealed that MAP@Dia could provide an effective solution for both P recycling and lead immobilization in contaminated soil.

Hydrogen Production from Energy Poplar Preceded by MEA Pre-Treatment and Enzymatic Hydrolysis

The need to pre-treat lignocellulosic biomass prior to dark fermentation results primarily from the composition of lignocellulose because lignin hinders the processing of hard wood towards useful products. Hence, in this work a two-step approach for the pre-treatment of energy poplar, including alkaline pre-treatment and enzymatic saccharification followed by fermentation has been studied. Monoethanolamine (MEA) was used as the alkaline catalyst and diatomite immobilized bed enzymes were used during saccharification. The response surface methodology (RSM) method was used to determine the optimal alkaline pre-treatment conditions resulting in the highest values of both total released sugars (TRS) yield and degree of lignin removal. Three variable parameters (temperature, MEA concentration, time) were selected to optimize the alkaline pre-treatment conditions. The research was carried out using the Box-Behnken design. Additionally, the possibility of the re-use of both alkaline as well as enzymatic reagents was investigated. Obtained hydrolysates were subjected to dark fermentation in batch reactors performed by Enterobacter aerogenes ATCC 13048 with a final result of 22.99 mL H₂/g energy poplar (0.6 mol H₂/mol TRS).

Aggregation and transport of rutile titanium dioxide nanoparticles with montmorillonite and diatomite in the presence of phosphate in porous sand

Crop soil is inevitably contaminated by the excess of phosphate (P) fertilizers. A large amount of nanoparticle titanium dioxide (nTiO₂) entered soils as well due to the wide use of engineered nanomaterials. It is of great urgency and a high priority to investigate the mechanisms of nTiO₂ deposition with the presence of P in crop soils. This study investigated the transport behavior of (1.0 g L^-1) rutile nTiO₂ with two representative clay particles (montmorillonite or diatomite) in the presence of P through the saturated quartz sand. In 10 mM NaCl electrolyte solution at pH 6.0, the recovery percentage of nTiO₂ was 36.3% from sand column. Nevertheless, it was reduced to 18.6% and 11.1% while montmorillonite and diatomite present in suspensions, respectively. Obviously, the improvement of nTiO₂ retention in sand was more pronounced by diatomite than montmorillonite. The likely mechanism for this result was that large aggregates were formed due to the attachment of nTiO₂ to montmorillonite and diatomite. Moreover, the surface of diatomite with the larger hydrodynamic radius was less negatively charged by comparison with montmorillonite. However, this phenomenon disappeared with the addition of P. P adsorption increases the repulsive force between particles and sand and the fast release of attached nTiO₂-montmorillonite and diatomite from sand. The two-site kinetic retention model and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the combination of k_1/k_1d, k₂ and secondary minimum energy can be used to accurately describe the attachment of nTiO₂-montmorillonite and diatomite to sand in the presence of P.

Towards "Precision Mining" of wastewater: Selective recovery of Cu from acid mine drainage onto diatomite supported nanoscale zerovalent iron particles

This paper introduces the concept of 'Precision Mining' of metals which can be defined as a process for the selective in situ uptake of a metal from a material or media, with subsequent retrieval and recovery of the target metal. In order to demonstrate this concept nanoscale zerovalent iron (nZVI) was loaded onto diatomaceous earth (DE) and tested for the selective uptake of Cu from acid mine drainage (AMD) and subsequent release. Batch experiments were conducted using the AMD and nZVI-DE at 4.0-16.0 g/L. Results demonstrate nZVI-DE as highly selective for Cu removal with >99% uptake recorded after 0.25 h when using nZVI-DE concentrations ≥12.0 g/L, despite appreciable concentrations of numerous other metals in the AMD, namely: Co, Ni, Mn and Zn. Cu uptake was maintained in excess of 4 and 24 h when using nZVI-DE concentrations of 12.0 and 16.0 g/L respectively. Near-total Cu release from the nZVI-DE was then recorded and attributed to the depletion of the nZVI component and the subsequent Eh, DO and pH recovery. This novel Cu uptake and release mechanism, once appropriately engineered, holds great promise as a novel 'Precision Mining' process for the rapid and selective Cu recovery from acidic wastewater, process effluents and leach liquors.

Gold decorated porous biosilica nanodevices for advanced medicine

Diatomite is a fossil material made of amorphous porous silica. In this work, polyethylene glycol (PEG)-modified diatomite NPs (PEG-DNPs) are decorated with gold NPs (AuNPs) by one-pot liquid-phase synthesis. Nanocomplexes (PEG-DNPs@AuNPs), with an average size of about 450 nm, are characterized by dynamic light scattering, electron microscopy, nitrogen adsorption/desorption analysis, UV-vis and photoluminescence spectroscopies. Preliminary studies on the use of the nanocomplex in nanomedicine are also presented. Tests performed incubating PEG-DNPs@AuNPs in physiological conditions reveal a good stability of material. Cellular uptake of labeled PEG-DNPs@AuNPs is investigated by confocal microscopy after incubation with human cervix epithelioid carcinoma (HeLa) cells up to 48 h: an efficient cytoplasmic localization is observed. In vitro cytotoxicity of nanocomplexes with a concentration up to 400 μg ml^-1 for 72 h is also evaluated. The results suggest the use of PEG-DNPs@AuNPs as advanced nanodevices adding imaging features to the nanocomplexes, due to AuNPs as contrast agent.

Effectiveness of an improved form of insecticide-based diatomaceous earth against four stored grain pests on different grain commodities

The effectiveness of Grain-Guard, an improved form of diatomaceous earth (DE), with low risk to the environment, was evaluated against the storage pests Liposcelis paeta, Cryptolestes ferrugineus, Rhyzopertha dominica, and Tribolium castaneum on four grain commodities, wheat, rice, maize and sorghum. The overall mortality of stored grain pests increased with the rise of application rate and exposure intervals of diatomaceous earth and decreased over 120 days of post-treatment period. Our results revealed that mortality of adults 14 days post-disclosure was > 80% on wheat at the start of post-treatment than rice, maize, and sorghum, respectively. During the first 60 days of post-treatment, adult mortality increased, whereas later on, a steady decrease in adult mortality was observed. Considerable differences in dose rates were observed on mortality levels along with grain commodities. Following 14 days of exposure, all adults of four species were dead on wheat at 100 ppm and on rice at 150 ppm except maize and sorghum. The suppression of progeny was noticeably higher at the beginning of post-treatment duration while after 60-days of post-treatment, progeny numbers started to increase with the rise in post-treatment durations. This new improved DE formulation was found to be effective at dose rates that are extensively lower than required with previous DE formulations and will contribute to lower the risk of health and environment.

Insecticidal effect and impact of fitness of three diatomaceous earths on different maize hybrids for the eco-friendly control of the invasive stored-product pest Prostephanus truncatus (Horn)

Diatomaceous earths (DEs) are able to successfully protect grain commodities from noxious stored-product insect and mite infestations; however, their effectiveness may be moderated by the grain hybrid or variety they are applied to. There is a gap of information on the comparison of the efficacy of different DEs when are applied on different maize hybrids against Prostephanus truncatus (Horn). Therefore, here we tested three commercially available DEs (DEA-P at 75 and 150 ppm, Protect-It at 500 ppm, and PyriSec at 500 ppm) on five different maize hybrids (Calaria, Doxa, Rio Grande, Sisco, and Studio) for the control of P. truncatus adults in terms of mortality (at 7 and 14 days), progeny production, properties of the infested maize hybrids (number and weight of kernels with or without holes, number of holes per kernel) and the adherence level of the tested DEs to the kernels. DEA-P was very effective at 75 ppm while a considerable proportion of the exposed P. truncatus adults was still alive after 14 days of exposure on all maize hybrids treated with 500 ppm of Protect-It or PyriSec, even though it was 3.3 times higher than the maximal application tested dose of DEA-P. Apart from parental mortality, DEA-P was able to reduce P. truncatus progeny production in all hybrids contrary to Protect-It or PyriSec. The adherence ratios were always higher for DEA-P than Protect-It or PyriSec to all maize hybrids. The highest numbers of kernels (or weight of kernels) without holes were noticed after their treatment with DEA-P. Doxa and Sisco performed better than Calaria, Rio Grande, or Studio based on the differences found concerning the numbers of kernels without holes at treatments with DEA-P and Protect-It. Overall, the findings of our study indicate the high potentiality of DEA-P as protectant of different maize hybrids to P. truncatus infestations at low doses, a fact that could help the eco-friendly management of this noxious species in the stored-product environment.

Internalization kinetics and cytoplasmic localization of functionalized diatomite nanoparticles in cancer cells by Raman imaging

Porous biosilica nanoparticles obtained from diatomites (DNPs) have been recently demonstrated to be non-toxic nanovectors of therapeutic agents in cancer cells. In this work, the internalization kinetics and intracellular spatial distribution of functionalized DNPs incubated with human lung epidermoid carcinoma cell line (H1355) up to 72 hours are investigated by Raman imaging. The label-free Raman results are compared with confocal fluorescence microscopy and photoluminescence (PL) data. Raman bands specifically assigned to DNPs and cellular components provide evidence that the nanovectors are internalized and co-localize with lipid environments. A considerable DNPs uptake in cells is observed within 6 hours, with equilibrium being achieved after 18 hours. The obtained data show the presence of DNPs up to 72 hours, without damage to cell viability or morphology. The PL measurements performed on DNPs not penetrating the cells at different incubation times are strongly correlated with the results obtained by Raman imaging and confocal microscopy analyses.

Dual delivery of hydrophilic and hydrophobic drugs from chitosan/diatomaceous earth composite membranes

Oral administration of drugs presents important limitations, which are frequently not granted the importance that they really have. For instance, hepatic metabolism means an important drug loss, while some patients have their ability to swell highly compromised (i.e. unconsciousness, cancer…). Sublingual placement of an accurate Pharmaceutical Dosage Form is an attractive alternative. This work explores the use of the β-chitosan membranes, from marine industry residues, composed with marine sediments for dual sublingual drug delivery. As proof of concept, the membranes were loaded with a hydrophilic (gentamicin) and a hydrophobic (dexamethasone) drug. The physico-chemical and morphological characterization indicated the successful incorporated of diatomaceous earth within the chitosan membranes. Drug delivery studies showed the potential of all formulations for the immediate release of hydrophilic drugs, while diatomaceous earth improved the loading and release of the hydrophobic drug. These results highlight the interest of the herein developed membranes for dual drug delivery.

Tylosin sorption to diatomaceous earth described by Langmuir isotherm and Freundlich isotherm models

Tylosin, an antibiotic used for maintaining livestock health, is a macrolide structurally similar to a number of important, often prescribed human antibiotics. Because of this relationship, tylosin presents a potential threat of antimicrobial resistance from environmental buildup. This work investigated tylosin sorption to natural diatomaceous earth product (DE) and the types of physical interactions responsible for sorption. Most sorption processes were best described by the Langmuir model when compared with Freundlich model. Heat of sorption (ΔH) was 1.14 kJ mol^-1 indicating a physisorption process. Change in entropy (ΔS) was 119 J mol^-1. Sorption was evaluated from aqueous solution with various H⁺, KCl and Urea concentrations. In 0.01 M phosphate buffer (PB) pH 6.6, a maximum sorption capacity of 15 mg tylosin per g of DE was achieved. Changing the pH to 2.9 or 11.2 resulted in decreased sorption of tylosin (13 and 10 mg g^-1, respectively). Addition of 1 M KCl to 0.01 M PB pH 6.6 decreased sorption of tylosin to DE with the maximum binding capacity of 7 mg g^-1. Sorption in 1.0 M urea, 0.01 M phosphate buffer pH 6.6 showed a maximum sorption of 13 mg g^-1. Based on these results, the sorption of tylosin appears to be a physisorption process, with charge-charge interactions being the mode of sorption at neutral pH and small contributions from secondary interactions. This information will be useful for developing effective strategies for mitigating tylosin and other antimicrobial's impact on the environment.

A single-tube approach for in vitro diagnostics using diatomaceous earth and optical sensor

Versatile, simple and efficient sample preparation is desirable for point-of-care testing of emerging diseases such as zoonoses, but current sample preparation assays are insensitive, labour-intensive and time-consuming and require multiple instruments. We developed a single-tube sample preparation approach involving direct pathogen enrichment and extraction from human specimens using diatomaceous earth (DE). Amine-modified DE was used to directly enrich a zoonotic pathogen, Brucella, in a large sample volume. Next, a complex of amine-modified DE and dimethyl suberimidate was used for nucleic acid extraction from the enriched pathogen. Using our single-tube approach, the pathogen can be enriched and extracted within 60min at a level of 1 colony formation unit (CFU) from a 1ml sample volume in the same tube. The performance of this approach is 10-100 times better than that of a commercial kit (102 to 103CFU/ml) but does not require a large centrifuge. Finally, we combined the single-tube approach with a bio-optical sensor for rapid and accurate zoonotic pathogen detection in human urine samples. Using the combination system, Brucella in human urine can be efficiently enriched (~ 8-fold) and the detection limit is enhanced by up to 100 times (1CFU/ml bacteria in urine) compared with the commercial kit. This combined system is fast and highly sensitive and thus represents a promising approach for disease diagnosis in the clinical setting.

Stabilization of heavy metals in municipal sewage sludge by freeze-thaw treatment with a blend of diatomite, FeSO4, and Ca(OH)2

In this work, the effects of diatomite with 15% FeSO₄•7H₂O and 7.5% Ca(OH)₂ on sludge stabilization were investigated using batch leaching tests. The influence of cell rupture caused by freezing and thawing on stabilization was also evaluated. The results indicated that the optimal diatomite percentage was 2%. Cell rupture by freezing and thawing reduced heavy metal leachability, followed by cell death and decrease of organic groups. The concentration of heavy metals in sludge leachate increased after cell rupture, indicating that the heavy metal leachability was reduced after freezing and thawings. Moreover, the stabilization effects were generally improved after freezing and thawing. As compared with the stabilization of the original sludge, the unstable fractions decreased and the residual fractions of the heavy metals increased in the stabilized sludge after cell rupture.

IMPLICATIONS

This study developed a method to stabilize heavy metals in municipal sewage sludge. Diatomite combined with FeSO₄·7H₂O and Ca(OH)₂ improved the treatment of sewage sludge contaminated by heavy metals. Cell lysis by freeze-thaw treatment reduced the risk of leaching heavy metals caused by cell death and decreased major organic groups in the sludge.

Removals of cryptosporidium parvum oocysts and cryptosporidium-sized polystyrene microspheres from swimming pool water by diatomaceous earth filtration and perlite-sand filtration

Removal of Cryptosporidium-sized microspheres and Cryptosporidium parvum oocysts from swimming pools was investigated using diatomaceous earth (DE) precoat filtration and perlite-sand filtration. In pilot-scale experiments, microsphere removals of up to 2 log were obtained with 0.7 kg·DE/m² at a filtration rate of 5 m/h. A slightly higher microsphere removal (2.3 log) was obtained for these DE-precoated filters when the filtration rate was 3.6 m/h. Additionally, pilot-scale perlite-sand filters achieved greater than 2 log removal when at least 0.37 kg/m² of perlite was used compared to 0.1-0.4 log removal without perlite both at a surface loading rate of 37 m/h. Full-scale testing achieved 2.7 log of microspheres and oocysts removal when 0.7 kg·DE/m² was used at 3.6 m/h. Removals were significantly decreased by a 15-minute interruption of the flow (without any mechanical agitation) to the DE filter in pilot-scale studies, which was not observed in full-scale filters. Microsphere removals were 2.7 log by perlite-sand filtration in a full-scale swimming pool filter operated at 34 m/h with 0.5 kg/m² of perlite. The results demonstrate that either a DE precoat filter or a perlite-sand filter can improve the efficiency of removal of microspheres and oocysts from swimming pools over a standard sand filter under the conditions studied.

Adsorption of methyl orange from aqueous solution using chitosan/diatomite composite

A novel chitosan/diatomite composite was prepared by a simple mixture in the mass ratio to remove methyl orange (MO) from aqueous media in this study. The composite adsorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy analysis. The parameters to influence the adsorption of MO were studied under such conditions as kinetics, adsorption isotherm, pH effect, and thermodynamics. The results revealed that adsorption of MO was initially rapid and the equilibrium time was reached after 40 min. The optimal value of the pH was 5.0 for better adsorption. The equilibrium data were well fitted to the Langmuir isotherm compared to the Freundlich isotherm, and exhibited the highest capacity and a removal rate of 88.37% under an initial dye concentration of 50 mg/L. The kinetic data were well described by the pseudo-second order model. The thermodynamic calculations revealed that the sorption was viable, spontaneous, and exothermic under the conditions studied. In addition, the chitosan/diatomite composite had good adsorption and desorption performance with respect to reusability after six cycles. These results showed that the chitosan/diatomite could be considered as a potential adsorbent for the removal of MO in aqueous solution.

Research of combined adsorption-coagulation process in treating petroleum refinery effluent

The petroleum refinery industry generates a significant amount of wastewater that contains a high level of organic matter, which calls for effective and costly treatments. In this research, the effectiveness of the petroleum refinery effluent (PRE) treatment with physicochemical process of combined adsorption and coagulation was evaluated. The effects of initial pH, hydraulic condition , and combined sequence of treatment process, different treating reagent types and dosages on the chemical oxygen demand (COD) removal were investigated. Additionally, the elimination efficiency of pollutant wastewater was monitored by gas chromatography-mass spectrometry (GC-MS), and Fourier transformed infrared (FT-IR) spectrophotometer was adopted to describe the structure of the wastewater. Wooden activated carbon was chosen as adsorbent at the dosage of 10 g/L as a primary treatment, and 1500 mg/L polymeric magnesium ferric sulfate was used in coagulation. Results showed that adsorption and subsequent coagulation displayed the best performance when initial pH was 9 at shear rates (G) of G1 = 65 s^-1 and G2 = 20 s^-1, which reached maximal removal rate of COD and total organic carbon GC-MS testing result revealed that adsorption was effective in phenols and iso-alkanes removal, whereas coagulation was good at removing esters and n-alkanes.

Microporous nano-MgO/diatomite ceramic membrane with high positive surface charge for tetracycline removal

A novel microporous nano-MgO/diatomite ceramic membrane with high positive surface charge was prepared, including synthesis of precursor colloid, dip-coating and thermal decomposition. Combined SEM, EDS, XRD and XPS studies show the nano-MgO is irregularly distributed on the membrane surface or pore walls and forms a positively charged nano coating. And the nano-MgO coating is firmly attached to the diatomite membrane via SiO chemical bond. Thus the nano-MgO/diatomite membrane behaves strong electropositivity with the isoelectric point of 10.8. Preliminary filtration tests indicate that the as-prepared nano-MgO/diatomite membrane could remove approximately 99.7% of tetracycline in water through electrostatic adsorption effect. The desirable electrostatic property enables the nano-MgO/diatomite membrane to be a candidate for removal of organic pollutants from water. And it is convinced that there will be a great application prospect of charged ceramic membrane in water treatment field.

Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation

The quest to reduce fluoride in groundwater to WHO acceptable limit of 1.5 mg/L to prevent diseases such as teeth mottling and skeletal fluorosis was the motivation for this study. Al/Fe oxide-modified diatomaceous earth was prepared and its defluoridation potential evaluated by batch method. The sorbent with pHpzc 6.0 ± 0.2 is very reactive. The maximum 82.3% fluoride removal attained in 50 min using a dosage of 0.3 g/100 mL in 10 mg/L fluoride was almost attained within 5 min contact time; 81.3% being the percent fluoride removal at 5 min contact time. The sorbent has a usage advantage of not requiring solution pH adjustment before it can exhibit its fluoride removal potential. A substantial amount of fluoride (93.1%) was removed from solution when a sorbent dosage of 0.6 g/100 mL was contacted with 10 mg/L fluoride solution for 50 min at a mixing rate of 200 rpm. The optimum adsorption capacity of the adsorbent was 7.633 mg/g using a solution containing initially 100 mg/L fluoride. The equilibrium pH of the suspensions ranged between 6.77 and 8.26 for 10 and 100 mg/L fluoride solutions respectively. Contacting the sorbent at a dosage of 0.6 g/100 mL with field water containing 5.53 mg/L at 200 rpm for 50 min reduced the fluoride content to 0.928 mg/L-a value below the upper limit of WHO guideline of 1.5 mg/L fluoride in drinking water. The sorption data fitted to both Langmuir and Freundlich isotherms but better with the former. The sorption data obeyed only the pseudo-second-order kinetic, which implies that fluoride was chemisorbed.

In vitro screening of natural feed additives from crustaceans, diatoms, seaweeds and plant extracts to manipulate rumen fermentation

BACKGROUND

Eight natural products from animal, unicellular algae, brown seaweed and plant origins were chosen according to their theoretical antimicrobial activity: Diatomaceous earths (DE), insoluble chitosan (ICHI), soluble chitosan (CHI), seaweed meal (SWM), Ascophyllum nodosum (ASC), Laminaria digitata (LAM), neem oil (NOIL) and an ivy fruit extract rich in saponins (IVY). Dose-response incubations were conducted to determine their effect on rumen fermentation pattern and gas production, while their anti-protozoal activity was tested using (14) C-labelled bacteria.

RESULTS

DE, SWM, NOIL and ICHI had very small effects on rumen function when used at inclusion rate up to 2 g L(-1) . ASC had anti-protozoal effects (up to -23%) promoting a decrease in gas production and methanogenesis (-15%). LAM increased VFA production (+7%) and shifted from butyrate to acetate. CHI also shifted fermentation towards propionate production and lower methane (-23%) and protozoal activity (-56%). IVY decreased protozoal activity (-39%) and ammonia concentration (-56%), as well as increased feed fermentation (+11% VFA concentration) and shifted from acetate to propionate production.

CONCLUSIONS

ASC, LAM, CHI and IVY showed promising potential in vitro as feed additives to improve rumen function, thus more research is needed to investigate their mode of action in the rumen microbial ecosystem. © 2015 Society of Chemical Industry.

[Differential Effect and Mechanism of in situ Immobilization of Cadmium Contamination in Soil Using Diatomite Produced from Different Areas]

In order to understand the difference of in situ immobilization effect and mechanism of Cd contamination in soil using diatomite produced from different areas, the test was conducted using diatomite produced from Yunnan Tengchong, Jilin Linjiang, Zhejiang Shengzhou and Henan Xinyang of China as modifiers to immobilize cadmium contamination in simulated soil. The results indicated that the diatomite from all the four producing areas could effectively immobilize available Cd in soil, decreasing the available Cd content in soil by 27.7%, 28.5%, 30.1% and 57.2%, respectively when the adding concentration was 30 g x kg(-1). Their ability for immobilizing available Cd in soil followed the sequence of Henan Xinyang > Zhejiang Shengzhou > Jilin Linjiang > Yunnan Tengchong. It was also found that the physical and chemical properties of diatomite played a main role in soil cadmium immobilization, lower bulk density, larger specific surface area, more micro pores and wider distribution range of aperture were more favorable for available Cd immobilization. The results also showed that, the diatomite could control Cd contamination by changing soil physical and chemical properties, among these properties, pH and organic matter content were the key factors, increasing soil pH value and organic matter content was favorable for available cadmium immobilization, while the soil water content had little effect on available cadmium immobilization. The control of soil cadmium contamination by using diatomite to change cation exchange capacity was limited by time in some degree. The diatomite produced from Henan Xinyang, Zhejiang Shengzhou and Yunnan Tengchong increased the soil pH value and organic matter content, and was favorable for available Cd immobilization, while the diatomite from Jilin Linjiang showed converse effect.

Hydrous iron oxide modified diatomite as an active filtration medium for phosphate capture

A simple method to functionalize diatomite with hydrous iron oxide was attempted and its performance as a new active filtration material to remove and recover phosphate from water was investigated under varying solution conditions. The Langmuir phosphate adsorption capacity increased from 0.6 mgP/g for raw diatomite to 4.89, 14.71, 25.02 mgP/g for hydrous iron oxide modified diatomite (HIOMD), depending on the amount of iron loaded. Loading of hydrous iron oxide caused the increase in true and bulk density and a decline in filtration rate, but to a lesser extent. It was shown that the HIOMD product with suitable iron content could retain a good filtration performance with a greatly increased adsorption capacity for phosphate. The phosphate adsorption increased by decreasing pH and by increasing ionic strength at high pH levels. The adsorption process was interpreted by ligand exchange. Coexisting oxyanions of sulfate, nitrate, citrate, carbonate, silicate and humic acid showed different effects on phosphate fixation but it was presumed that their influence at their concentrations and pH levels commonly encountered in effluent or natural waters was limited, i.e., HIOMD had a reasonably good selectivity. Results in repeated adsorption, desorption and regeneration experiment showed that the adsorbed phosphate could be recovered and the material could be reused after regeneration. The column test showed that HIOMD could be potentially utilized as an adsorption filtration medium for phosphate removal and recovery from water.

Enhanced coagulation for improving coagulation performance and reducing residual aluminum combining polyaluminum chloride with diatomite

The feasibility of using enhanced coagulation, which combined polyaluminum chloride (PAC) with diatomite for improving coagulation performance and reducing the residual aluminum (Al), was discussed. The effects of PAC and diatomite dosage on the coagulation performance and residual Al were mainly investigated. Results demonstrated that the removal efficiencies of turbidity, dissolved organic carbon (DOC), and UV254 were significantly improved by the enhanced coagulation, compared with PAC coagulation alone. Meaningfully, the five forms of residual Al (total Al (TAl), total dissolved Al (TDAl), dissolved organic Al (DOAl), dissolved monomeric Al (DMAl), and dissolved organic monomeric Al (DOMAl)) all had different degrees of reduction in the presence of diatomite and achieved the lowest concentrations (0.185, 0.06, 0.053, 0.014, and 0 mg L(-1), respectively) at a PAC dose of 15 mg L(-1) and diatomite dose of 40 mg L(-1). In addition, when PAC was used as coagulant, the majority of residual Al existed in dissolved form (about 31.14-70.16%), and the content of DOMAl was small in the DMAl.

Adsorption of crystal violet with diatomite earth&carbon by a modification of hydrothermal carbonization process

The high colority and difficulty of decolorization are the most important tasks on printing and dyeing wastewater. This study investigates the ability of diatomite earth&carbon (DE&C) as an adsorbent to removal crystal violet (CV) from aqueous solutions. Fourier transform infrared spectroscopy results indicate the importance of functional groups during the adsorption of CV. The obtained N2 adsorption-desorption isotherm values accord with well IUPAC type II. Our calculations determined a surface area of 73.15 m(2) g(-1) for DE&C and an average pore diameter of 10.56 nm. Equilibrium data of the adsorption process fitted very well to the Langmuir model (R(2) > 0.99). The results of kinetics study showed that the pseudo-second-order model fitted to the experimental data well. The thermodynamic parameters were also evaluated. ΔH° <0, ΔS° > 0 and ΔG° < 0 demonstrated that the adsorption process was spontaneous and exothermic for dye. Furthermore the positive value of ΔS° reflected good affinity of the CV dye.

Nanoscale zero-valent iron incorporated with nanomagnetic diatomite for catalytic degradation of methylene blue in heterogeneous Fenton system

Nanoscale zero-valent iron (nZVI) incorporated with nanomagnetic diatomite (DE) composite material was prepared for catalytic degradation of methylene blue (MB) in heterogeneous Fenton system. The material was constructed by two facile steps: Fe3O4 magnetic nanoparticles were supported on DE by chemical co-precipitation method, after which nZVI was incorporated into magnetic DE by liquid-phase chemical reduction strategy. The as-prepared catalyst was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, magnetic properties measurement and nitrogen adsorption-desorption isotherm measurement. The novel nZVI@Fe3O4-diatomite nanocomposites showed a distinct catalytic activity and a desirable effect for degradation of MB. MB could be completely decolorized within 8 min and the removal efficiency of total organic carbon could reach to 90% after reaction for 1 h.

Surface bioengineering of diatomite based nanovectors for efficient intracellular uptake and drug delivery

Diatomite is a natural porous silica material of sedimentary origin. Due to its peculiar properties, it can be considered as a valid surrogate of synthetic porous silica for nano-based drug delivery. In this work, we exploit the potential of diatomite nanoparticles (DNPs) for drug delivery with the aim of developing a successful dual-biofunctionalization method by polyethylene glycol (PEG) coverage and cell-penetrating peptide (CPP) bioconjugation, to improve the physicochemical and biological properties of the particles, to enhance the intracellular uptake in cancer cells, and to increase the biocompatibility of 3-aminopropyltriethoxysilane (APT) modified-DNPs. DNPs-APT-PEG-CPP showed hemocompatibility for up to 200 μg mL(-1) after 48 h of incubation with erythrocytes, with a hemolysis value of only 1.3%. The cytotoxicity of the modified-DNPs with a concentration up to 200 μg mL(-1) and incubation with MCF-7 and MDA-MB-231 breast cancer cells for 24 h, demonstrated that PEGylation and CPP-bioconjugation can strongly reduce the cytotoxicity of DNPs-APT. The cellular uptake of the modified-DNPs was also evaluated using the above mentioned cancer cell lines, showing that the CPP-bioconjugation can considerably increase the DNP cellular uptake. Moreover, the dual surface modification of DNPs improved both the loading of a poorly water-soluble anticancer drug, sorafenib, with a loading degree up to 22 wt%, and also enhanced the drug release profiles in aqueous solutions. Overall, this work demonstrates that the biofunctionalization of DNPs is a promising platform for drug delivery applications in cancer therapy as a result of its enhanced stability, biocompatibility, cellular uptake, and drug release profiles.

CO2 adsorption on diatomaceous earth modified with cetyltrimethylammonium bromide and functionalized with tetraethylenepentamine: Optimization and kinetics

The carbon dioxide (CO2) adsorbent diatomaceous earth (DE) was modified with cetyltrimethylammonium bromide (CTAB) and functionalized with varying levels of tetraethylenepentamine (TEPA). The CO2 absorption at atmospheric pressure was optimized by varying the TEPA-loading level (0-40% (w/w)), operating temperature (40-80 °C) and water vapor concentration (0-16% (v/v)) in a 10% (v/v) CO2 feed stream in helium balance using a full 2(3) factorial design. The TEPA/CTAB-DE adsorbents were characterized by X-ray diffractometry, Fourier transform infrared spectrometry and thermogravimetric analyses. The CO2 adsorption capacity increased as each of these three factors increased. The TEPA loading level-water concentration interaction had a positive influence on the CO2 adsorption while the operating temperature-water concentration interaction was antagonistic. The optimal condition for CO2 adsorption on 40%TEPA/CTAB-DE, evaluated via a factorial design response surface method (RSM), was a temperature of 58-68 °C and a water vapor concentration of 9.5-14% (v/v), with a maximum CO2 adsorption capacity of 149.4 mg g(-1) at 63.5 °C and 12% (v/v) water vapor concentration in the feed. Validation and sensitivity tests revealed that the estimated CO2 adsorption capacity was within ±4% of the experimental values, suggesting that the RSM model was satisfied and acceptable. From three kinetic models (pseudo-first-order, pseudo-second-order model and Avrami's equation), assessed using an error function (Err) and the coefficient of determination (R(2)), Avrami's equation was the most appropriate to describe the kinetics of CO2 adsorption on the 40%TEPA/CTAB-DE adsorbent and suggested that more than one reaction pathway occurred in the CO2 adsorption.

[Removal Kinetics and Mechanism of Aniline by Manganese-oxide-modified Diatomite]

A novel rapid green one-step method was developed for the preparation of manganese modified diatomite (Mn-D) by treating roasted diatomite with an acidic permanganate solution. The effects of calcination temperature and mass ratio of KMnO4 and diatomite (p) on aniline removal efficiency of Mn-D were investigated. The removal kinetics and mechanism of aniline by Mn-D were also discussed. The results showed that when the optimal calcination temperature was 450 degrees C, p was 1.6, and the loading amounts of δ-MnO2 was 0.82 g x g(-1), Mn-D had a great performance for aniline removal, and more than 80% of aniline was adsorbed within 10 minutes, accompanied with the release of Mn2+. In acidic conditions, the adsorption process on Mn-D followed pseudo-second-order and was mainly controlled by intra-particle diffusion. The best fitting of the experimental adsorption data was given by the Freundlich equation. Gas chromatograph-mass spectrometer was applied to identify the reaction intermediates at different times, and azobenzene was found to be the main reaction intermediate in the degradation system. Based on the above observations, the possible degradation pathway of aniline by Mn-D was proposed.

Modified natural diatomite and its enhanced immobilization of lead, copper and cadmium in simulated contaminated soils

Natural diatomite was modified through facile acid treatment and ultrasonication, which increased its electronegativity, and the pore volume and surface area achieved to 0.211 cm(3) g(-1) and 76.9 m(2) g(-1), respectively. Modified diatomite was investigated to immobilize the potential toxic elements (PTEs) of Pb, Cu and Cd in simulated contaminated soil comparing to natural diatomite. When incubated with contaminated soils at rates of 2.5% and 5.0% by weight for 90 days, modified diatomite was more effective in immobilizing Pb, Cu and Cd than natural diatomite. After treated with 5.0% modified diatomite for 90 days, the contaminated soils showed 69.7%, 49.7% and 23.7% reductions in Pb, Cu and Cd concentrations after 0.01 M CaCl2 extraction, respectively. The concentrations of Pb, Cu and Cd were reduced by 66.7%, 47.2% and 33.1% in the leaching procedure, respectively. The surface complexation played an important role in the immobilization of PTEs in soils. The decreased extractable metal content of soil was accompanied by improved microbial activity which significantly increased (P<0.05) in 5.0% modified diatomite-amended soils. These results suggested that modified diatomite with micro/nanostructured characteristics increased the immobilization of PTEs in contaminated soil and had great potential as green and low-cost amendments.

Facile preparation of hierarchically porous diatomite/MFI-type zeolite composites and their performance of benzene adsorption: the effects of NaOH etching pretreatment

Hierarchically porous diatomite/MFI-type zeolite (Dt/Z) composites with excellent benzene adsorption performance were prepared. The hierarchical porosity was generated from the microporous zeolite coated at the surface of diatom frustules and from the macroporous diatomite support. A facile NaOH etching method was employed for the first time to treat the frustule support, followed by hydrothermal growth of MFI-type zeolite at the surface of frustules previously seeded with nanocrystalline silicalite-1 (Sil-1). NaOH etching enlarged the pores on diatom frustules and further increased the coated zeolite contents (W(z)). The central macropore size of the diatom frustules increased from approximately 200-500 nm to 400-1000 nm after NaOH etching. The W(z) could reach 61.2%, while the macroporosity of the composites was largely preserved due to more voids for zeolite coating being formed by NaOH etching. The Dt/Z composites exhibited higher benzene adsorption capacity per unit mass of zeolite and less mass transfer resistance than Sil-1, evaluated via a method of breakthrough curves. These results demonstrate that etching of a diatomite support is a facile but crucial process for the preparation of Dt/Z composites, enabling the resulting composites to become promising candidates for uses in volatile organic compounds emission control.