Removal of Tetrabromobisphenol A by adsorption on pinecone-derived activated charcoals: Synchrotron FTIR, kinetics and surface functionality analyses

Biomass-derived cellulose nanocrystals modified nZVI for enhanced tetrabromobisphenol A (TBBPA) removal

Nano zero-valent iron (nZVI) is an advanced environmental functional material for the degradation of tetrabromobisphenol A (TBBPA). However, high surface energy, self-agglomeration and low electron selectivity limit degradation rate and complete debromination of bare nZVI. Herein, we presented biomass-derived cellulose nanocrystals (CNC) modified nZVI (CNC/nZVI) for enhanced TBBPA removal. The effects of raw material (straw, filter paper and cotton), process (time, type and concentration of acid hydrolysis) and synthesis methods (in-situ and ex-situ) on fabrication of CNC/nZVI were systematically evaluated based on TBBPA removal performance. The optimized CNC-S/nZVI(in) was prepared via in-situ liquid-phase reduction using straw as raw material of CNC and processing through 44 % H2SO4 for 165 min. Characterizations illustrated nZVI was anchored to the active sites at CNC interface through electrostatic interactions, hydrogen bonds and FeO coordinations. The batch experiments showed 0.5 g/L CNC-S/nZVI(in) achieved 96.5 % removal efficiency at pH = 7 for 10 mg/L initial TBBPA. The enhanced TBBPA dehalogenation by CNC-S/nZVI(in), involving in initial adsorption, reduction process and partial detachment of debrominated products, were possibly attributed to elevated pre-adsorption capacity and high-efficiency delivery of electrons synergistically. This study indicated that fine-tuned fabrication of CNC/nZVI could potentially be a promising alternative for remediation of TBBPA-contaminated aquatic environments.

Effect of hydrothermal carbonization on pyrolysis behavior, nutrients and metal species distribution in municipal sludge

In this study, the effect of hydrothermal carbonation (HTC) on the pyrolysis behavior and the distribution of nutrients and metal species of waste-activated sludge (WAS) was investigated. Results showed that the pyrolysis activation energy range of WAS decreased from 11 to 57 kJ/mol to 10-36 kJ/mol when the hydrothermal carbonization was at 160 °C. As indicated by thermodynamic parameters, the hydrothermal carbonization process reduces the pyrolysis reaction activity of the hydrochar. The results of the chemical analysis indicate that hydrothermal carbonization significantly enhances the release of phosphorus and nitrogen, with maximum recovery at a temperature of 200 °C. The standard measurement and testing protocol revealed that hydrothermal carbonization increased the content of non-apatite inorganic P fraction in hydrochar and enhanced the availability of P. Heavy metal analysis shows that hydrothermal carbonization can strengthen the stability of heavy metals in WAS.

Toxicity, physiological response, and biosorption mechanism of Dunaliella salina to copper, lead, and cadmium

Background

Heavy metal pollution has become a global problem, which urgently needed to be solved owing to its severe threat to water ecosystems and human health. Thus, the exploration and development of a simple, cost-effective and environmental-friendly technique to remove metal elements from contaminated water is of great importance. Algae are a kind of photosynthetic autotroph and exhibit excellent bioadsorption capacities, making them suitable for wastewater treatment.

Methods

The effects of heavy metals (copper, lead and cadmium) on the growth, biomolecules accumulation, metabolic responses and antioxidant response of Dunaliella salina were investigated. Moreover, the Box-Behnken design (BBD) in response surface methodology (RSM) was used to optimize the biosorption capacity, and FT-IR was performed to explore the biosorption mechanism of D. salina on multiple heavy metals.

Results

The growth of D. salina cells was significantly inhibited and the contents of intracellular photosynthetic pigments, polysaccharides and proteins were obviously reduced under different concentrations of Cu2+, Pb2+ and Cd2+, and the EC50 values were 18.14 mg/L, 160.37 mg/L and 3.32 mg/L at 72 h, respectively. Besides, the activities of antioxidant enzyme SOD and CAT in D. salina first increased, and then descended with increasing concentration of three metal ions, while MDA contents elevated continuously. Moreover, D. salina exhibited an excellent removal efficacy on three heavy metals. BBD assay revealed that the maximal removal rates for Cu2+, Pb2+, and Cd2+ were 88.9%, 87.2% and 72.9%, respectively under optimal adsorption conditions of pH 5-6, temperature 20-30°C, and adsorption time 6 h. Both surface biosorption and intracellular bioaccumulation mechanisms are involved in metal ions removal of D. salina. FT-IR spectrum exhibited the main functional groups including carboxyl (-COOH), hydroxyl (-OH), amino (-NH2), phosphate (-P=O) and sulfate (-S=O) are closely associated with the biosorption or removal of heavy metalsions.

Discussion

Attributing to the brilliant biosorption capacity, Dunaliella salina may be developed to be an excellent adsorbent for heavy metals.

Genome-Centric Metatranscriptomic Characterization of a Humin-Facilitated Anaerobic Tetrabromobisphenol A-Dehalogenating Consortium

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in electronics manufacturing, has caused global contamination due to improper e-waste disposal. Its persistence, bioaccumulation, and potential carcinogenicity drive studies of its transformation and underlying (a)biotic interactions. This study achieved an anaerobic enrichment culture capable of reductively dehalogenating TBBPA to the more bioavailable bisphenol A. 16S rRNA gene amplicon sequencing and quantitative PCR confirmed that successive dehalogenation of four bromide ions from TBBPA was coupled with the growth of both Dehalobacter sp. and Dehalococcoides sp. with growth yields of 5.0 ± 0.4 × 108 and 8.6 ± 4.6 × 108 cells per μmol Br- released (N = 3), respectively. TBBPA dehalogenation was facilitated by solid humin and reduced humin, which possessed the highest organic radical signal intensity and reducing groups -NH2, and maintained the highest dehalogenation rate and dehalogenator copies. Genome-centric metatranscriptomic analyses revealed upregulated putative TBBPA-dehalogenating rdhA (reductive dehalogenase) genes with humin amendment, cprA-like Dhb_rdhA1 gene in Dehalobacter species, and Dhc_rdhA1/Dhc_rdhA2 genes in Dehalococcoides species. The upregulated genes of lactate fermentation, de novo corrinoid biosynthesis, and extracellular electron transport in the humin amended treatment also stimulated TBBPA dehalogenation. This study provided a comprehensive understanding of humin-facilitated organohalide respiration.

Lipidomic profiling reveals phenotypic diversity and nutritional benefits in Ficus carica L. (Fig.) seed cultivars

Introduction

Ficus carica L. seeds are a substantial source of minor oil with high unsaturation levels and potent antioxidant properties. The study aims to evaluate the mineral composition, lipodomic profile, and vibrational fingerprints of 22 fig genotypes utilizing FTIR-ATR techniques and chemometrics.

Methods

FTIR-ATR spectroscopy and chemometric techniques were employed to examine the phenotypic diversity of fig seeds. The investigation was performed in detail. The research analyzed twenty-two fig genotypes to assess their nutritional properties, genetic relationships, and potential applications.

Results

The results demonstrate substantial nutritional benefits related to fig seeds, which could serve as genetic resources for selection programs for extracting vegetable oil and functional ingredients. Additionally, a detailed lipodomic profile analysis led to the categorization of the genotypes into four unique clusters. The study uncovered new insights regarding the nutritional composition of the samples, while also highlighting significant similarities and differences. The findings showcased the phenotypic diversity within the studied fig germplasm, which is likely attributed to underlying genetic factors. These accessions offer a valuable gene pool for future breeding programs and diverse applications involving fig seeds.

Discussion

This work contributes to the selection of potential genotypes for scientific and industrial purposes. Furthermore, the application of FTIR and chemometrics revealed a noteworthy diversity of patterns, emphasizing the previously underestimated significance of this aspect in evaluating the chemodiversity of the species.

Contrasting effects of a novel biochar-microalgae complex on arsenic and mercury removal

Biochar and algae were commonly used as environmental-friendly adsorbents to treat wastewater contaminated with heavy metals. In the study, we used a biochar-microalgae complex of Coconut shell activated carbon (Csac) and Chlorella to evaluate and compare the adsorption ability of arsenic and mercury. The adsorption kinetic study showed that the adsorption efficiency of the biochar-microalgae complex for mercury was better remarkably than arsenic (about 74.84% higher in initial 1 min and 71.62% higher at adsorption equilibrium), which could be interpreted as the complex had excellent adsorption capacity for mercury. The new biochar-microalgae complex adsorbed up to 46.8 μg·g^-1 of mercury at 100 μg·L^-1 concentration. FTIR and XPS indicated that the surface of biochar-microalgae complex adsorbent had abundant oxygen-containing functional groups that could provide active sites during the adsorption process, i.e., -COOH, -OH and C-O-C et al. Compared with arsenic, the adsorption peaks of mercury moved or changed significantly, suggesting that the complex strongly adsorbed mercury and the main adsorption mechanisms were the ion exchange and complexation between functional groups and mercury ion. What must be emphasized was arsenic mainly existed as negative ions (AsO₂^-, AsO₂^3-) in water, which was the reason for the weak adsorption capacity of the biochar-microalgae complex for arsenic. In short, the adsorption efficiency and performance of the biochar-microalgae complex was significantly higher than that of arsenic (p < 0.01), and the adsorption of mercury by biochar-microalgae was chemisorption based on the single molecular layer theory.

Adsorption and Removal of Tetrabromobisphenol A by Adsorption on Functionalized Mesoporous Silica Nanotubes: Isotherms, Kinetics, Thermodynamics, and Optimization via Box-Behnken Design

In pursuit of environmental safety, a novel and efficient method-dispersive solid-phase extraction based on functionalized mesoporous silica nanotubes (FMSNT nanoadsorbent)-was developed to remove tetrabromobisphenol A (TBBPA) from water samples. Characterization and comprehensive analysis of the FMSNT nanoadsorbent, including maximum adsorption capacity of 815.85 mg g^-1 for TBBPA and its water stability, confirmed its potential. Subsequent analysis revealed the impact of multiple factors, for instance pH, concentration, dose, ionic strength, time, and temperature, on the adsorption process. The findings revealed that the adsorption of TBBPA followed the Langmuir and pseudo-second-order kinetics models while primarily driven by hydrogen bond interactions between bromine ions or hydroxyl groups of TBBPA and amino protons around the cavity. The novel FMSNT nanoadsorbent showed high stability and efficiency even after five times of recycling. Moreover, the overall process was identified as chemisorption, endothermic, and spontaneous. Finally, the Box-Behnken design was applied to optimize the results, confirming good reusability even after five cycles.

Preparation of a Molecularly Imprinted Silica Nanoparticles Embedded Microfiltration Membrane for Selective Separation of Tetrabromobisphenol A from Water

The ubiquitous presence of tetrabromobisphenol A (TBBPA) in aquatic environments has caused severe environmental and public health concerns; it is therefore of great significance to develop effective techniques to remove this compound from contaminated waters. Herein, a TBBPA imprinted membrane was successfully fabricated via incorporating imprinted silica nanoparticles (SiO₂ NPs). The TBBPA imprinted layer was synthesized on the 3-(methacryloyloxy) propyltrimethoxysilane (KH-570) modified SiO₂ NPs via surface imprinting. Eluted TBBPA molecularly imprinted nanoparticles (E-TBBPA-MINs) were incorporated onto a polyvinylidene difluoride (PVDF) microfiltration membrane via vacuum-assisted filtration. The obtained E-TBBPA-MINs embedded membrane (E-TBBPA-MIM) showed appreciable permeation selectivity toward the structurally analogous to TBBPA (i.e., 6.74, 5.24 and 6.31 of the permselectivity factors for p-tert-butylphenol (BP), bisphenol A (BPA) and 4,4'-dihydroxybiphenyl (DDBP), respectively), far superior to the non-imprinted membrane (i.e., 1.47, 1.17 and 1.56 for BP, BPA and DDBP, respectively). The permselectivity mechanism of E-TBBPA-MIM could be attributed to the specific chemical adsorption and spatial complementation of TBBPA molecules by the imprinted cavities. The resulting E-TBBPA-MIM exhibited good stability after five adsorption/desorption cycles. The findings of this study validated the feasibility of developing nanoparticles embedded molecularly imprinted membrane for efficient separation and removal of TBBPA from water.

Adsorption mechanism of Cr(VI) on woody-activated carbons

To provide guidance for the selection of woody-activated carbon in the treatment of wastewater containing hexavalent chromium (Cr(VI)), the adsorption tests on two varieties of commercial woody-activated carbon powder from different manufacturers were carried out. The physicochemical properties and structural characteristics of activated carbon were studied by using elemental, chemical, and instrumental analyses. The adsorption mechanism of Cr(VI) was discussed by investigating the factors affecting the removal of hexavalent chromium. The two kinds of woody-activated carbon have microporous and mesoporous structures. Commercial woody-activated carbon No.1 (ACI) has a more extensive specific surface area and a better-developed pore structure. While ACI exhibits a higher adsorption capability when the content of Cr(VI) is high, commercial woody-activated carbon No.2 (AC) can remove hexavalent chromium fast when the concentration is low. A rise in pH value is not helpful for the materials to remove Cr(VI) from solutions. For Cr(VI) removal, the optimum pH value is 2. The adsorption of Cr(VI) by AC and ACI followed the pseudo-second-order kinetic model and Langmuir isothermal adsorption equation. The maximum adsorption value of Cr(VI) is 154.56 mg/g for AC and 241.55 mg/g for ACI. There is chemical adsorption during the Cr(VI) removal. A lot of Cr (Ⅲ) was formed by Cr(VI). The abundance of pores and the reducing ability of the materials are essential for the removal of Cr(VI).

Synthesis of biochar-CoFe2O4 nanocomposite for adsorption of methylparaben from wastewater under full factorial experimental design

The presence of endocrine-disrupting chemicals in municipal wastewater has emerged as a threat to human health and the environment. Therefore, this study aimed to develop biochar-cobalt ferrite (BCF) nanocomposite for the removal of methylparaben from water under the full factorial experimental design of 4 factors with 3 levels (3⁴). The biochar-CoFe₂O₄ nanocomposite was developed by co-precipitation method from cobalt ferrite and biochar of Eucalyptus tree bark. Adsorbent surface morphology and functional and elemental composition were carried out by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) techniques which showed the presence of cracks with a rough surface, reasonable surface chemical composition, and many chemical functional groups, respectively. The experimental and predicted adsorption efficiencies ranged from 25.3 to 85.6% and 21.8 to 80.3%, respectively. The maximum adsorption performance (85.6%) reduced the methylparaben concentration from 27.5 to 4.0 mg/L at the optimum condition of adsorbent dose of 55 mg/100 mL, pH 6, contact time 90 min, and the initial methylparaben concentration of 27.5 mg/L. However, the adsorbent dose was the most influential main factor whereas the least influential was the interaction between solution pH and contact time under the regression model. The model also showed that 69% methylparaben removal was described by the regression model. The experimental data best fitted with the Freundlich model indicate multilayer adsorption which is the implication of physisorption. The sorption mechanism is attributed to Vander Waals forces, H-bonding, and dipole interaction. This BCF nanocomposite adsorbent appears to be promising for the removal of methylparaben from wastewater, but a further optimization process is essential to boost the treatment performance.

Adsorption of tetracycline by Nicandra physaloides (L.) Gaertn seed gum and Nicandra physaloides(L.) Gaertn seed gum/Carboxymethyl chitosan aerogel

In this study, novel aerogels of Nicandra physaloides (L.) Gaertn seed gum (NPG) and Nicandra physaloides (L.) Gaertn seed gum/Carboxymethyl chitosan (NPG/CMC) were prepared by freeze-drying method for removing tetracycline (TC) from water. Scanning electron microscope (SEM), X-ray diffraction (XRD),Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) were used to characterize structure and morphology of NPG and NPG/CMC aerogels. The average pore diameter of NPG and NPG/CMC were 3.04 and 1.2 nm, the specific surface areas were 2.67 and 0.73 m²/g, respectively. The maximum adsorption capacity of NPG and NPG/CMC aerogels for TC based on Langmuir isotherm was 266.7 and 332.23 mg/g respectively. Through thermodynamic and kinetic studies, it was found that the adsorption processes of the two adsorbents were spontaneous and followed the pseudo-second-order kinetic model. And the process of NPG adsorption of TC was endothermic, while NPG/CMC was exothermic.

An updated review on environmental occurrence, scientific assessment and removal of brominated flame retardants by engineered nanomaterials

Due to the extensive manufacturing and use of brominated flame retardants (BFRs), they are known to be hazardous, bioaccumulative, and recalcitrant pollutants in various environmental matrices. BFRs make flame-resistant items for industrial purposes (textiles, electronics, and plastics equipment) that are disposed of in massive amounts and leak off in various environmental matrices. The consumption of plastic items has expanded tremendously during the COVID-19 pandemic which has resulted into the increasing load of solid waste on land and water. Some BFRs, such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDs), are no longer utilized or manufactured owing to their negative impacts, which promotes the utilization of new BFRs as alternatives. BFRs have been discovered worldwide in soil, sludge, water, and other contamination sources. Various approaches such as photocatalysis-based oxidation/reduction, adsorption, and heat treatment have been found to eradicate BFRs from the environment. Nanomaterials with unique properties are one of the most successful methodologies for removing BFRs via photocatalysis. These methods have been praised for being low-cost, quick, and highly efficient. Engineered nanoparticles degraded BFRs when exposed to light and either convert them into safer metabolites or completely mineralize. Scientific assessment of research taking place in this area during the past five years has been discussed. This review offers comprehensive details on environmental occurrence, toxicity, and removal of BFRs from various sources. Degradation pathways and different removal strategies related to data have also been presented. An attempt has also been made to highlight the research gaps prevailing in the current research area.

Removal of Cr(VI) from aqueous solution by a novel ZnO-sludge biochar composite

The incorporation of ZnO into biochar has become a promising way to obtain adsorbents with enhanced adsorption capacity. In this study, a low-cost ZnO-sludge biochar composite (ZBC) was prepared by a simply in situ method using sewage sludge biochar (SBC) and zinc acetate, as well as employed for Cr(VI) adsorption in water. The results of XPS and FT-IR suggested that the ZBC surface had more functional groups such as -COOH, -OH, -C-O, ZnO, etc. Compared with SBC, the BET-specific surface area of the ZBC increased from 8.82 to 41.24 m²·g^-1, which provides potential advantages for Cr(VI) uptake. Benefiting from ZnO incorporation, about an 18% increase in Cr(VI) removal efficiency was obtained. The maximum removal efficiency and equilibrium adsorption amount of ZBC for Cr(VI) reached 98.4% and 33.87 mg·g^-1, respectively. The adsorption was spontaneous and endothermic nature, and coincided nicely with pseudo-second-order kinetics and Langmuir isotherm. The analyses indicated that Cr(VI) removal by ZBC was predominantly via electrostatic attraction, surface complexation, ion exchange, and reduction. This study provided valuable insights into the problem of sludge disposal and provided a new and effective method for Cr(VI) removal.

Control of organic contaminants in groundwater by passive sampling and multivariate statistical analysis

Organic contaminants in groundwater are among the most challenging chemical compound contaminants today, particularly when it comes to understanding their occurrence, origin, and relations in groundwater, as well as the transport processes, fate, and environmental impacts involved. This paper presents the use of active carbon fibre (AFC) passive sampling and multivariate statistical processing of the results to predict the possible occurrence of organic compounds (OCs) in groundwater and to determine the origin of various anthropogenic activity. This study aims to deepen our knowledge on the control of OCs in groundwater by introducing a multi-analytical and multi-elemental holistic approach, using the Dravsko polje aquifer, the largest intergranular aquifer in Slovenia, as an example. The occurrence of OCs in groundwater was determined by means of ACFs and compared against the characteristics of the recharge area and the type of compounds detected. We combined hierarchical cluster analysis (HCA) and principal component analysis (PCA) to identify the relationship between different OCs in groundwater. The relationships between their occurrence, environmental setting and type of compound were determined using multiple linear regression (MLR). From the total of 343 organic compounds detected using passive sampling, 47 were included in further statistical analysis. MLR shows that the environmental setting is one of the most important factors affecting the different types of pollutants in groundwater. MLR models were calculated for different sources of pollution (agricultural, urban, and industrial) based on the environmental setting, land use, agglomeration, infrastructure networks, and hydrogeological characteristics of the aquifer. By means of HCA and PCA, we identified the relationships between different OCs in groundwater. As expected, the strongest correlations were found between primary compounds and their degradation products (e.g. atrazine and desethylatrazine) and compounds of similar use (e.g. atrazine and propazine, also desethylatrazine and propazine, atrazine and simazine). Some of them were also found to have a similar molecular structure (e.g. palmitic and stearic acid, 5-methoxygramine and 5-methoxytryptamine). The use of the same substances in different environments (agricultural/urban) makes them markers of both (different) origins. Therefore, it is particularly important to determine the combination of markers of different origin using multivariate statistical methods, especially in the case of mixed land use. This study identifies the main factors influencing the distribution of groundwater OCs and thus contributes to a more comprehensive understanding of the vulnerability of shallow groundwater to surface-derived contamination in similar environments.

Modification of sludge-based biochar using air roasting-oxidation and its performance in adsorption of uranium(VI) from aqueous solutions

Modification methods for sludge-based biochar are often complex and generally ineffective. In this study, sludge-based biochars were prepared at low cost using a simple air roasting-oxidation modification method and the adsorption performance on U(VI) was investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results together indicated that more carbon-oxygen functional groups were formed on the surface of oxidized biochar (OBC) compared to unoxidized biochar (BC). The adsorption performance of 550-OBC (biochar oxidized at 550 °C) on U(VI) was explored in batch experiments. The maximum adsorption capacity was up to 490.2 mg/g at 25 °C and pH 6, exceeding most of the reported biochars. 550-OBC also showed good adsorption performance at low U(VI) concentration, with 96% removal at pH 6 and an initial U(VI) concentration of 1 mg/L. Density functional theory (DFT) calculations indicated that the H-bond length between the solvated U(VI) and functional groups on the OBC was about 1.7 Å, which forms stronger H-bonds between them compared to that between U(VI) and BC (4.21 Å), and the adsorption energy value for this complex was highly negative -31.82 kcal/mol. In addition, 550-OBC exhibited high selectivity for U(VI) adsorption and excellent regeneration performance, making it a cost-effective and high-performance adsorbent.

Effects of microplastics on the accumulation and neurotoxicity of methylmercury in zebrafish larvae

Microplastics (MPs) and methylmercury (MeHg) have attracted increasing attention due to ubiquitous occurrence and toxicity. This study aimed to investigate whether MPs could absorb MeHg and thus modify its bioconcentration and neurotoxicity in the zebrafish larvae (Danio rerio). The pseudo-second-order model (R² = 0.989) was found to be suitable for describing the adsorption kinetics of MeHg onto MPs. Compared with Freundlich and Temkin models, the Langmuir isotherm model provided a better fit with the experimental data exhibiting a maximum monolayer adsorption capacity of 54.945 mg/g. These results suggested that adsorption occurs mainly by a chemical process dominated by monolayer adsorption. MPs adsorbed MeHg to form MPs/MeHg complex, which was ingested by zebrafish larvae, and promoted accumulation of MeHg. Thus, the presence of MPs aggravated the reduction of locomotor activity induced by MeHg, and downregulation of neurotransmitters related genes, such as ache, gfap and scl1A3b. Metabolome analysis also revealed disrupted glutathione (GSH) metabolism upon exposure of MeHg alone and in combination with MPs, as reflected by the increased in the ratio of GSH and oxidized glutathione. These effects were also confirmed by upregulation of oxidative stress-related genes, such as sod, sod mt and gpx4a. Collectively, these results indicated that MPs could act as a carrier of MeHg and enhance its accumulation in zebrafish, thereby disrupting locomotor activity by excessive oxidative stress. This study provides a scientific basis for improving health risk assessment of environmental pollutants, particularly those potentially able to adsorb to MPs by virtue of their chemical nature.

Study on the mechanism of biochar loaded typical microalgae Chlorella removal of cadmium

Coconut shell activated carbon (Csac) is one of the most widely used materials to remove cadmium (Cd) from contaminated water. A large diversity of microorganisms exists in various aquatic systems and may aid Cd removal by Csac. In this study, we explored the reactions of Csac with microalgae (Chlorella) in Cd-containing media. The results of scanning electron microscope (SEM) imaging, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), superconducting pulse-Fourier transform nuclear magnetic resonance (pulse-FT NMR) and X-ray photoelectron spectroscopy (XPS) indicated that Chlorella could adhere in the micropores of Csac formed Csac@Chlorella composite adsorbent loading Chlorella. Furthermore, the composite adsorbent surface had abundant functional groups such -COOH, -OH and C-O-C, which served as active sites during the adsorption process. Compared with Csac, Csac@Chlorella had an enhanced Cd adsorption capacity evidently. The results showed that pH 8, 0.2 g Csac, OD₆₈₀ of 0.1 for Chlorella were optimal conditions for maximum Cd adsorption capacity within one hour contact time. Furthermore, the Cd adsorption process was well described by the pseudo-second-order and Langmuir adsorption isotherm models. The models revealed that the adsorption process was mainly based on chemical adsorption of a single molecular layer, accompanied by electrostatic attraction, complexation and intracellular adsorption, amongst other parameters. Collectively, the findings illustrate that the microalgae (Chlorella)-Csac-Cd interaction is complex and will thus have immense interest to a broad range of biological, environmental, and geoscience communities.

Remediation of Chromium (VI) from Groundwater by Metal-Based Biochar under Anaerobic Conditions

Iron salt-modified biochar has been widely used to remove Cr(VI) pollution due to the combination of the generated iron oxides and biochar, which can bring positive charge and rich redox activity. However, there are few comprehensive studies on the methods of modifying biochar with different iron salts. In this study, two iron salt (FeCl3 and Fe(NO3)3) modification methods were used to prepare two Fe-modified biochar materials for removing Cr(VI) in simulated groundwater environment. It was revealed by systematic characterization that FeCl3@BC prepared via the FeCl3 modification method, has larger pore size, higher zeta potential and iron oxide content, and has higher Cr(VI) adsorption-reduction performance efficiency as compared to Fe(NO3)3@BC prepared via Fe(NO3)3 modification method. Combined with XRD and XPS analyses, Fe3O4 is the key active component for the reduction of Cr(VI) to Cr(III). The experimental results have shown that acidic conditions promoted Cr(VI) removal, while competing ions (SO42− and PO43−) inhibited Cr(VI) removal by FeCl3@BC. The Elovich model and intra-particle diffusion model of FeCl3@BC can describe the adsorption behavior of Cr(VI) well, indicating that both the high activation energy adsorption process and intra-particle diffusion control the removal process of Cr(VI). The Freundlich model (R2 > 0.999) indicated that there were unevenly distributed chemisorptions centers on the FeCl3@BC surface. Stability experiments exposed that FeCl3@BC was stable under neutral, acidic, and alkaline conditions. Furthermore, the main mechanisms of FeCl3@BC removal of Cr(VI) include electrostatic adsorption, chemical reduction, ion exchange, and co-precipitation. In conclusion, our findings provide a new insight for the selection of iron salt-modified biochar methods, and will also be beneficial for the preparation of more efficient Fe-modified biochars in the future.

Experimental design for the optimization of paraquat removal from aqueous media using a fixed-bed column packed with Pinus Eldarica stalks activated carbon

In this study, a fixed-bed column packed with an activated carbon (Pinus eldarica stalks (PES-AC)) was used to evaluate the performance of paraquat removal from wastewater. The effect of bed height, initial paraquat concentration, contact time, flow rate on the removal of paraquat was investigated using response surface methodology (RSM) based on central composite design (CCD). From the RSM model, the optimum experimental conditions to achieve 94.65% removal of paraquat were solution pH of 8.0, 6 mg L^-1 of paraquat, 4 mL min^-1 of flow rate, 0.8 cm of the bed height, and 40 min of contact time. The breakthrough data were significantly fitted with Thomas, bed depth services time (BDST), and Yoon-Nelson models. The high values of N_BD (14.33, 32.29, and 54.46 mg L^-1) and critical bed depth (0.396, 0.370, and 0.330 cm) obtained from BDST model revealed the high efficiency and suitability of the adsorbent. Adsorption of paraquat on PES-AC was strongly dependent on solution pH, indicating an electrostatic attraction mechanism.

Efficient removal of plastic additives by sunlight active titanium dioxide decorated Cd-Mg ferrite nanocomposite: Green synthesis, kinetics and photoactivity

Large use of flame retardants or additives in plastic industries have caused scientific attention as their leaching from consumer products is indicative of environmental concern. Moreover, plastic additives have proven features of endocrine disruptors, genotoxicity and persistence. Therefore, photodegradation of tetrabromobisphenol A (TBBPA) and bisphenol A (BPA) were explored in water. Seeing environmental safety, titanium dioxide decorated magnesium substituted cadmium ferrite (CdMgFe₂O₄@TiO₂) was synthesized by using plant extract of M. koenigii via co-precipitation. Sharp peaks obtained in PXRD ensured high crystallinity and purity of distorted spherical nanocomposite (5-25 nm). Subsequently, CdMgFe₂O₄@TiO₂ nanocatalyst was evaluated for the effective elimination of plastic additives at variable reaction parameters (pollutant: 2-10 mgL^-1; catalyst: 5-25 mg; pH: 3-7, dark-sunlight). With 20 mg of catalytic dose, CdMgFe₂O₄@TiO₂ showed maximum degradation of 2 mgL^-1 of TBBPA (91%) and BPA (94%) at neutral pH under sunlight. Considerable reduction in persistence of TBBPA (t_1/2:2.4 h) and BPA (t_1/2:2.1 h) indicated admirable photoactivity of CdMgFe₂O₄@TiO₂. Results were supported by BET, zeta potential, band reflectance and photoluminescence analysis that indicated for higher surface area (90 m²g^-1), larger particle stability (-20 mV), lower band gap (1.9 eV) and inhibited charge-pairs recombination in nanocomposite. Degradation consisted of initial Langmuir-adsorption followed by first order kinetics. Scavenger analysis revealed the role of hydroxyl radical in photodegradation studies. Nanocomposite was effective up to eight cycles without any significant loss of activity that advocated its high-sustainability and cost-effectiveness. Overall, with excellent surface characteristics, green synthesized CdMgFe₂O₄@TiO₂ nanocomposite is a promising and alternative photocatalyst for industrial applications.

A practical method to remove perfluorooctanoic acid from aqueous media using layer double hydride system: a prospect for environmental remediation

Perfluorooctanoic acid (PFOA) is an organic compound that is persistent and very toxic to living organisms and the environment. In this study, two kinds of Mg-Al-layered double hydroxides (namely LDH-1 and 2) were synthesized using hydrothermal and dry grinding methods and used to adsorb PFOA from aqueous solution. The kinetic study revealed that a pseudo-2nd order model was the best method for describing the kinetics of sorption, which could emphasize the chemical interaction between PFOAs and LDHs. Among the models tested, the Freundlich model was the best fit for the sorption isotherms. The removal rates of PFOA adsorption by LDH-1 and LDH-2 were 90% and 98.9%, respectively, in the lowest time compared with similar past studies using different adsorbents. The currently synthesized LDHs showed the least equilibrium time, without thermal treatment and the need for activation. The research bears prospects for removing PFOA from aqueous media, thereby demonstrating the potential of employing synthesized LDHs in a fixed-bed filter for the environmental remediation of PFOA-contaminated wastewater bodies.

Preparation of sludge biochar rich in carboxyl/hydroxyl groups by quenching process and its excellent adsorption performance for Cr(VI)

A facile pyrolysis-quenching-reroasting process was developed to prepare a sludge-based biochar adsorbent, and its adsorption performance for Cr(VI) ions was investigated. The unquenched biochar (U-BC) and quenched biochar (Q-BC) were systematically compared and characterized. Fourier transform infrared spectroscopy (FTIR) results showed that more carbon and oxygen functional groups such as -COOH and -OH were formed on the surface of Q-BC. These functional groups could be used as active sites during the adsorption process and help to improve the adsorption performance of the material. The results of Brunauer-Emmett-Teller (BET) analysis showed that the specific surface area of U-BC biochar was 523.36 m²/g, while the specific surface area of Q-BC biochar after quenching treatment increased to 785.3 m²/g. The adsorption performance of Q-BC biochar was studied, and the effects of pH, contact time and temperature on the adsorption performance of the material were explored. The pseudo-second-order model and Langmuir isotherm model indicated that the removal of Cr(VI) by Q-BC biochar material was a chemical adsorption-based adsorption process. At a temperature of 298 K and a pH of 1, the maximum Cr(VI) adsorption capacity of the quenched Q-BC biochar is as high as 291.54 mg/g, which was much higher than the maximum adsorption capacity of U-BC biochar (91.46 mg/g). This pyrolysis-quenching-reroasting process to prepare modified biochar provides a new, economical and effective way for the preparation of high-performance adsorption materials from municipal sludge.

The effects of biochar/compost for adsorption behaviors of sulfamethoxazole in amended wetland soil

Biochar and compost were two common amendments for the polluted soil. However, few studies were conducted to study the sorption of organic pollutants on combined biochar-compost and the relative adsorption mechanisms in mixed soil. The work had studied the adsorption and desorption behaviors of sulfamethoxazole (SMX) onto wetland soil after amended with biochar and/or compost. Moreover, the physicochemical and morphology properties of biochar/compost and amended soils were analyzed to discuss the relative adsorption mechanisms. Studies showed that the adsorption capacity of amended soils increased with the total amount of biochar or/and compost added, which was positively related to SOM, CEC, and EC of amended soils, but had nothing to do with the type of additives. Compared with the compost-treated treatments, the biochar-treated treatments generally achieved lower desorption rates, which also had demonstrated both different adsorption mechanisms. Pore filling and hydrophobic partitioning were the main adsorption mechanisms for biochar and compost, respectively. Though biochar owned developed pore structure, however, pore-filling of biochar was overwhelmingly weakened due to pore-blocking in mixed soils. Hence, in soil environment, compost is a kind of a more desirable amendment than biochar in absorbing and degrading organic pollutants.

Effective adsorption of bisphenol A from aqueous solution over a novel mesoporous carbonized material based on spent bleaching earth

In this study, the novel mesoporous carbonized material (HSBE/C) was prepared from clay/carbon composite (SBE/C) treated with hydrofluoric acid (HF) for the first time, and was employed to efficiently adsorb bisphenol A (BPA) in water. Specifically, SBE/C was derived from the pyrolysis of spent bleaching earth (SBE), an industrial waste. HF removed SiO₂ from SBE/C and increased the specific surface area of HSBE/C (from 100.21 to 183.56 m²/g), greatly providing more adsorption sites for enhanced BPA adsorption capacity. The Langmuir monolayer maximum adsorption capacity of HSBE/C (103.32 mg/g) was much higher than the commercial activated carbon (AC) (42.53 mg/g). The adsorption process by HSBE/C followed well with the Freundlich isotherm model and the pseudo-second-order kinetic model and also was endothermic (ΔH⁰ > 0) and spontaneous (ΔG⁰ < 0). Based on the systematic characterization and factor experiment (temperature, dosage, initial pH, co-existing ions), BPA adsorption mechanism by HSBE/C likely included the hydrogen bonding, electrostatic interaction, and hydrophobic interaction. Moreover, there was no secondary pollution during the total adsorption process. Extraordinary, HSBE/C manifested stability by NaOH desorption regeneration. This study provides a new sight for application of waste-based materials as the promising adsorbents in the treatment of endocrine disruptors.

Adsorption of neutral red dye by chitosan and activated carbon composite films

Research indicates the use of adsorbent materials to remove pollutants from wastewater and effluents, which can be obtained from renewable materials such as biomass, biopolymers (chitosan) or composites. Thus, the objective of this work was to produce and evaluate activated carbon (AC) and chitosan composite films as adsorbents of neutral red dye. AC films were produced using CO₂ and water vapor. The variables of the activation process were time (1 and 2 h) and temperature (600 and 750 °C). Five films were produced, with one pure chitosan (T1) film and four activated carbon with chitosan films (T2, T3, T4 and T5). The T2 film refers to activated carbon produced at 600 °C for 1 h + chitosan, T3 to activated carbon produced at 600 °C for 2 h + chitosan, T4 to activated carbon produced at 750 °C for 1 h + chitosan and T5 to activated carbon produced at 750 °C for 2 h + chitosan. The T5 film increased its adsorption capacity by approximately 87% and its removal efficiency of neutral red dye by 43% compared to T1. The presence of activated carbon in the films provided an increase in the adsorption capacity of the neutral red dye.

Preparation of composite soybean straw-based materials by LDHs modifying as a solid sorbent for removal of Pb(ii) from water samples

In this study, the nanocomposites from biomass (soybean straw) and layered double hydroxides (LDHs), denoted as B/LDHs, were fabricated using the mechanical-hydrothermal method. The obtained B/LDHs nanocomposites were characterized by TEM, SEM, FT-IR, and N2 adsorption–desorption techniques. Adsorption of the heavy-metal ions Pb(ii) on the B/LDHs was determined at 25°C and pH 6.0 using a batch technique. The experimental results demonstrated that biomass contributed to the sorption process. The pseudo-second-order, Langmuir, and Freundlich models well fitted the sorption process, indicating chemisorption and monolayer adsorption were the main adsorption mechanisms. Meanwhile, it is found that there is an obvious effect of adsorbent concentration in the studied adsorption system. In comparison with soybean straw and Mg–Al LDHs, the B/LDHs nanocomposites exhibit significantly enhanced sorption capacities. It is evident from this study that the construction of B/LDHs nanocomposites is an effective strategy for improving the sorption capacity of LDHs, and the modified LDH-based adsorbent shows a good potential in the removal of heavy metals from water. More importantly, it solves the problem of a large number of agricultural waste disposals. And, it achieved the goal of a win-win situation.

Optimize the preparation of Fe3O4-modified magnetic mesoporous biochar and its removal of methyl orange in wastewater

In this paper, Eichhornia Crassipes stems were used as biomass feedstock, and Fe²⁺ was used as the precursor solution to prepare Fe₃O₄-modified magnetic mesoporous biochar (Fe₃O₄@BC). By using Box-Behnken design (BBD) response surface methodology, the influences of three preparation parameters (X₁ = Fe²⁺ concentration, X₂ = pyrolysis temperature and X₃ = pyrolysis time) on the adsorption of methyl orange (MO) by Fe₃O₄@BC were investigated, and a reliable response surface model was constructed. The results show that X₁X₂ and X₁X₃ have a significant influence on the adsorption of MO by Fe₃O₄@BC. The surface area and pore volume of Fe₃O₄@BC are controlled by all preparation parameters. The increase of pyrolysis time will significantly reduce the -OH on the surface of Fe₃O₄@BC and weaken its MO adsorption capacity. Through the numerical optimization of the constructed model, the optimal preparation parameters of Fe₃O₄@BC can be obtained as follows: Fe²⁺ concentration = 0.27 mol/L, pyrolysis temperature = 405 °C, and pyrolysis time = 3.2 h. The adsorption experiment shows that the adsorption of Fe₃O₄@BC to MO is a spontaneous exothermic process, and the adsorption capacity is maximum when pH = 4. The adsorption kinetics and adsorption isotherms of Fe₃O₄@BC to MO conform to the pseudo-second-order kinetics and Sips model, respectively. Mechanism analysis shows that electrostatic interaction and H bond formation are the main forces for Fe₃O₄@BC to adsorb MO. This research not only realizes a new way of resource utilization of Eichhornia Crassipes biomass but also enriches the preparation research of magnetic biochar.

Synthesis and characterization of activated carbon from sugar beet residue for the adsorption of hexavalent chromium in aqueous solutions

A series of micro–mesoporous activated carbons (ACs) were prepared from sugar beet residue by a two-step method including KOH chemical activation and were used for Cr(vi) removal from aqueous solutions. Several characterization techniques, including SEM, TEM, N₂ adsorption, XRD, FTIR, and Raman spectroscopy, were used to determine the chemical and physical characteristics of the ACs, and the adsorption properties of the ACs were tested. The results indicated that the high specific surface area of the ACs reached 2002.9 m² g⁻¹, and the micropore surface area accounts for 85% of the total area. The optimal conditions for achieving the maximum Cr(vi) adsorption capacity of 163.7 mg g⁻¹ by the ACs were activation with a KOH/carbon ratio of 3.0, an initial Cr(vi) concentration of 400 mg L⁻¹, an adsorbent dose of 2.0 g L⁻¹ and pH of 4.5. Therefore, the ACs exhibit excellent adsorption performance for removing Cr(vi) from aqueous solutions. According to an investigation of the adsorption process, the adsorption isotherm is most consistent with the Langmuir isotherm model, and the adsorption kinetics were well described by the pseudo-second-order model.

A series of micro–mesoporous activated carbons (ACs) were prepared from sugar beet residue by a two-step method including KOH chemical activation and were used for Cr(vi) removal from aqueous solutions.

Exploration of nanocellulose washing agent for the green remediation of phenanthrene-contaminated soil

Polycyclic aromatic hydrocarbons are hazardous contaminants existing ubiquitously in polluted soil. In this study, using nanocellulose (CNC) fluid as an eco-friendly agent was proposed for the first time in the remediation of phenanthrene (PHE) contaminated soil. The effects of environmental factors on the mobilization of PHE in soil by CNC nanofluid was investigated using factorial analysis. The results showed that temperature and ionic strength had a significant influence on PHE removal, which were associated with the viscosity and zeta potential change in the nanofluid. The analysis based on two-dimensional correlation spectroscopy integrated with FTIR and synchrotron-based XRF imaging revealed that metals and minerals in soil played important roles in PHE detachment. The hydroxyl groups on CNC bonded with Fe-O, Si-O, and Mn-O in soil as time went on, and eventually achieved PHE mobilization through the interruption of PHE/SOM-metal/mineral linkages. The complexation and transport of PHE/SOM-metals/minerals from soil particles to the aqueous phase could be the primary PHE removal mechanism. Besides, the biotoxicity study displayed a detoxification effect of CNC nanofluid on PHE contaminants in soil. This study offers new insight into a cost-effective and biodegradable nanocellulose washing agent, which can be a good alternative to the available site remediation options.

An efficient Egeria najas-derived biochar supported nZVI composite for Cr(VI) removal: Characterization and mechanism investigation based on visual MINTEQ model

Egeria najas is a submerged aquatic plant, and the literatures on resourcification of submerged aquatic plant biochar remain limited. Until now, there has been no study on submerged aquatic plant biochar supported nZVI that is widely applied for removal of diversified contaminants in solution. In this study, an efficient approach to the preparation of Egeria najas-derived biochar supported nZVI composite is first developed for Cr(VI) removal in wastewater. The adsorption behavior and mechanism of Cr(VI) removal on the as-prepared Egeria najas-derived biochar/nZVI (EN@nZVI) composite were investigated. The results of FTIR and XPS indicate that the EN@nZVI surface had many functional groups such as R-COOH, R-OH, R-NH₂ and R-C-O-C, etc, which could provide active sites during the adsorption process. The BET results showed that the EN@nZVI had large specific surface area and average pore, which were 142.49 m²/g and 9.85 nm, respectively. EN@nZVI demonstrated high reactivity for Cr(VI) removal. Compared with nZVI, Cr(VI) removal efficiency by EN@nZVI is 50% higher than that of nZVI within 0.5 h. Furthermore, the maximum adsorption capacity of Cr (VI) was 56.79 mg/g and the energy of activation (E_a) was 31.30 kJ/mol. The adsorption process was well described by the pseudo-second order model and Sips adsorption isotherm model. The reaction mechanism of Cr(VI) removal was a multi-step removal mechanism, involving adsorption, surface complex formation, reduction and ion exchange reaction.

Brushite-infused polyacrylonitrile nanofiber adsorbent for strontium removal from water

The Fukushima Daiichi nuclear disaster and the decommissioning of over a hundred nuclear reactors worldwide led to the increase in the demand for efficient water treatment technologies to remove radionuclides, such as ⁹⁰Sr. Brushite or dicalcium phosphate dihydrate (DCPD) is a potential adsorbent to remove strontium from water. In this study, composite poly(acrylonitrile) (PAN) nanofiber (NF) adsorbents with DCPD (PAN/DCPD) were prepared, characterized, and investigated for strontium adsorption in water. Material characterization revealed mechanically suitable, hydrophilic, and macroporous composite NF adsorbents with average fiber diameters of <500 nm. As-prepared DCPD powder exhibited a superior strontium uptake capacity of 81.7 mg g^-1 at pH ≅ 10 of aqueous Sr²⁺ solution over its biogenic and synthetic predecessor, hydroxyapatite. Increased DCPD loading resulted in higher adsorption. Maximum Sr²⁺ uptake of PAN/DCPD NF with 70 wt% DCPD loading (PAN/70DCPD NF) was 146 mg g^-1 considering the Sips isotherm model. Kinetic studies revealed that Sr²⁺ removal by PAN/DCPD NF was a chemisorption process which involved ion exchange and surface complexation. PAN/70DCPD NF as a dead-end membrane filter exhibited superior removal efficiency over pure PAN NF. The overall results of this study revealed the potential application of PAN/DCPD NF adsorbent for ⁹⁰Sr removal from water.

Functional PVDF ultrafiltration membrane for Tetrabromobisphenol-A (TBBPA) removal with high water recovery

Tetrabromobisphenol-A (TBBPA) is one of the most important brominated flame retardants (BFRs), accounting for 60% of the total commercial BFR market. Increasing amounts of TBBPA and byproducts are released to the aquatic environment due to their extensive utilization in various sectors. However, research on the treatment of TBBPA contaminated wastewater using membrane filtration is still lacked. Herein, a PVDF10-PAA-ZrO₂ membrane was successfully developed and applied for the treatment of high-concentration TBBPA wastewater with super-high water recovery. The membrane was obtained through surface functionalization with nano-ZrO₂ from commercial PVDF ultrafiltration (UF) membrane. Compared to the commercial PVDF membrane, the developed membrane exhibited 4 times of permeate flux which was up to 200 L/m² min with comparable TBBPA rejection rate. Furthermore, the mechanisms of membrane development and TBBPA rejection were explored through synchrotron-based ATR-FTIR and X-ray analyses. It was revealed that ZrO₂ NPs were immobilized into membrane surface through binding with PAA layer, where the O of the carboxyl group combined with the Zr⁴⁺ on the ZrO₂ NP surface to form C-O-Zr bond through monodentate and bridging-bidentate modes. The sieving function of membrane could be the main mechanism of TBBPA removal. This research demonstrated a practical route and solid insight toward the development of highly efficient membrane for TBBPA removal. The proposed PVDF10-PAA-ZrO₂ membrane can also be promising for other industrial separation and purification applications.

Efficient removal of tetrabromobisphenol A (TBBPA) using sewage sludge-derived biochar: Adsorptive effect and mechanism

Sewerage sludge-derived biochars (SSDBCs) with high adsorption capacity and excellent recyclability were synthesized to remove tetrabromobisphenol A (TBBPA) in aqueous system. Scanning electron microscopy, elemental mapping via energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the morphology, composition, and microstructures. The maximum adsorption capacity of SSDBCs was about 87.02 mg g^-1 at 303 K and pH 7.5. The Langmuir isotherm demonstrated that the adsorption was mainly homogeneous and chemical processes. The kinetics of TBBPA removal well fitted the second-order dynamic model. Thermodynamic analysis showed that the adsorption was exothermic. The effect of π-π dispersive force and hydrogen bonding was proven as the main adsorption mechanism. Multiple cycle runs experiment revealed the excellent stability of recycled SSDBCs. This work provided a promising method of sludge resourceful treatment using an efficient, economic, cyclic, and convenient material for typical organic contaminant in the environment.

Ultrahigh adsorbability towards different antibiotic residues on fore-modified self-functionalized biochar: Competitive adsorption and mechanism studies

An ultrasonic-assistant fore-modified method was designed to develop the self-functionalized biochar (SFB) with enhanced adsorbability. Characterized by different morphologies, SFB was presenting particular groups of carbon micro-spheres. Possessing ultrahigh surface area of 2368 m²/g, SFB exhibited excellent adsorption capacity (up to 497 mg/g) towards traditional antibiotic. Besides, more functional groups, which played important roles on the solid-liquid interface interaction, posed on the surface of SFB. The removal efficiency of levofloxacin was up to 99.93 % in the competitive system. Adsorption mechanism was analyzed based on the results of FTIR, kinetics, isotherms and competitive adsorption experiments. The chemisorption affinity on the solid-liquid interface was strong enough, which was proved by isotherms, thermodynamics and K_d analyses. Meanwhile, SFB has presented a good resistance against humid acid interference in aqueous environment. Thus, the ultrasonic-assistant fore-modified method was potential in dramatically improving the feature of biochars. SFB presented excellent adsorbability to antibiotics and exhibits extraordinary potential in wastewater treatment.

Three-dimensional hierarchical porous carbon structure derived from pinecone as a potential catalyst support in catalytic remediation of antibiotics

In this study, pinecone was converted via two stage pyrolysis to produce low cost activated carbon. Furnace pyrolysis was used in the first step to convert pinecone to carbonized material, followed by microwave pyrolysis of the carbonized material activated with KOH to obtain activated carbon (ACK) materials as a suitable catalyst support. The ACK samples were characterized by their morphology, structural, adsorption and electrochemical properties. The optimized ACK 2.24-16 prepared from the pinecone had a complex three-dimensional (3D)-hierarchical porous structure, with an abundance of micropores and mesopores compared to other ACK samples judging from the high iodine number (1900 mg g^-1) and the methylene blue number (4000 mg g^-1) capacity. The optimized ACK 2.24-16 had the highest current response and least charge transfer resistance, along with moderate surface area (427 m² g^-1) as a promising photocatalyst support. The 3D hierarchical porous ACK significantly assisted catalyst dispersion, and enhanced visible light absorption and fast interfacial charge transfer. This work shows the promising aspect of utilizing pinecone to produce a low-cost photocatalyst support for environmental remediation.

Oxidation of tetrabromobisphenol A (TBBPA) by peroxymonosulfate: The role of in-situ formed HOBr

The degradation of tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame retardant, was evaluated during peroxymonosulfate (PMS) oxidation. TBBPA degradation was pH-dependent, with peak degradation rate constants occurring at pH 8.0-9.0, which was distinct from some other phenolic compounds. Singlet oxygen and radicals were found to play negligible roles in TBBPA degradation. TBBPA oxidation by PMS mainly proceeded via a direct oxidation pathway and the in-situ formed HOBr was found to greatly accelerate its degradation rates. The values of species-specific second-order rate constants for the reactions of PMS with the TBBPA k_HSO5-+TBBPA, k_HSO5-+TBBPA- and k_{HSO5-+TBBPA2-} were determined to be (1.11 ± 0.84) × 10^-2, (8.05 ± 2.31) × 10^-2, and (1.34 ± 0.25) × 10^-1 M^-1 s^-1, respectively, while the reaction rate constants for HOBr/OBr^- with TBBPA k_HOBr+TBBPA, k_HOBr+TBBPA-, k_HOBr+TBBPA2-and k_OBr-+TBBPA2- were determined to be (9.38 ± 2.10) × 10³, (1.59 ± 0.56) × 10⁵, (8.22 ± 0.41) × 10⁶, and (1.81 ± 0.12) × 10⁶ M^-1 s^-1, respectively. The bromine mass balance analysis showed that bromide ion and HOBr/OBr^- occupied 19.5% of total Br and brominated organic compounds accounted for the remaining percentages at pH 7.0. No formation of bromate was observed. Based on the identified products, a reaction pathway was proposed, which included oxidation, β-scission, hydroxylation, and dimerization reaction pathways. The results indicate that unactivated PMS is useful for the remediation of TBBPA contaminated water.

Batch and fixed-bed column adsorption of tetrabromobisphenol A onto metal organic resin: equilibrium, kinetic and mechanism studies

MORs were prepared through fabricating MOFs and resin for effective TBBPA removal in fix-bed column experiments from contaminated waters.

Three-dimensional high performance free-standing anode by one-step carbonization of pinecone in microbial fuel cells

In this paper, the free-standing macroporous carbon anode is prepared by one-step carbonization of pinecone without any further modification. The obtained anode is N, P-codoped porous carbon material, which is beneficial for electrochemical active bacterial adhesion and the fast start-up of cells. Both of the output voltage and long-term operation stability of the obtained anode are higher than that of carbon felt. The charge transfer resistance after biofilm formation is only 1.4 Ω, being 85.1% lower than that of carbon felt anode. 16S rRNA gene sequence analysis shows that Geobacter soli is the main electricigen and its ratio at the obtained anode is much higher than that at carbon felt (77.4% vs 34.0%). The N, P-codoped carbon as the three-dimensional free-standing anode has excellent electrochemical properties and is low cost and easy preparation. Most importantly, it enhances extracellular electron transfer, thus has potential application in microbial fuel cells.

Coupling mesoporous imprinted polymer based DGT passive samplers and HPLC: A new tool for in-situ selective measurement of low concentration tetrabromobisphenol A in freshwaters

Accurate measurement of tetrabromobisphenol A (TBBPA) is very important because of its widespread environmental pollution. Diffusive gradients in thin films technique (DGT), an in-situ passive sampling method, is regarded as a reliable and robust measurement technique. A new DGT technique based on mesoporous imprinted polymer was combined with high-pressure liquid chromatography (HPLC) method for sampling, preconcentration and monitoring low concentration TBBPA in natural waters. The diffusion coefficient of TBBPA through the diffusive gel was measured by diffusion cell test and simulated using mathematical expression. The effects of different ambient conditions were tested under laboratory conditions and the performance of DGT sampler was validated in natural waters. The diffusion coefficient of TBBPA in the diffusive gel was measured as 2.18 × 10^-6 cm² s^-1 and simulated as in the range 1.41-3.48 × 10^-6 cm² s^-1 by Amsden model. Comparison of experimental and theoretical data, the validity of the experimental method can be verified by the mathematical model. The binding agent with mesoporous imprinted polymer showed selective affinity to TBBPA and its adsorption rate met the requirement of DGT device. The DGT method detection limit was at the level of ng L^-1 for 7 days deployment. DGT sampler was suitable for application in aquatic environment with a range of pH (4.5-7.6), ionic strength (1 × 10^-4 - 0.5 mol L^-1), and dissolved organic matter (DOM) concentration (0-10 mg C L^-1). The coupling method of DGT and HPLC was a promising technique for in situ sampling, preconcentration and monitoring low concentration TBBPA in most typical natural waters.

RR2 dye adsorption to Hymenaea courbaril L. bark activated carbon associated with biofilm

This study addressed the removal performance of RR2 from aqueous solutions in adsorption columns experiments by comparing the potential of activated carbon alone (ACA) and microbially inoculated (MIAC), prepared from barks of a largely available tree in Brazilian Cerrado biome, Hymenaea courbaril L. or "Jatobá," presenting the kinetics, isotherms, breakthrough curves, and dissolved organic carbon removal. ACA presented strong interaction to RR2 dye, evidenced at the first 20 min when absorbance already attained 66.4%. The removal percentage gradually increased with time and the equilibrium occurred around 91.7% within 120 min. Langmuir model best fitted the isotherm data, indicating a maximum adsorption capacity of 4.068 mg g^-1 for the amount of 0.5 g of adsorbent. The Langmuir's model parameters K_L, R_L, and R² corresponded to 0.0234 L mg^-1, 0.4159, and 0.9663, respectively, indicating a favorable adsorption process (0 < R_L < 1). The experiments in adsorption columns revealed maximum adsorption capacities of 14.38 and 11.43 mg g^-1 for MIAC and ACA, respectively, where the microbial activity favorably retarded the adsorption breakpoint in approximately 20 min and enhanced the RR2 consumption in 25.8%. Effectiveness of DOC removal attained above 90% for both ACA and MIAC, reducing the content from 86.1 to 7.84 mg L^-1 and 4.82 mg L^-1, respectively.

Exploratory of immobilization remediation of hydroxyapatite (HAP) on lead-contaminated soils

This study was aimed to investigate the adsorption and fixation effects of hydroxyapatite (HAP) on lead-contaminated soil. According to the experimental results, the microstructure of hydroxyapatite was observed by a scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) showed that OH^- and PO₄^3- were the main functional groups in HAP. Optimum adsorption conditions of Pb²⁺ were obtained: 0.2 g/L, adsorbent; initial solution pH of 5.5; and contact time of 120 min. The kinetic adsorption experiments were carried out with the initial lead solution concentrations of 50 mg/L, 150 mg/L, and 250 mg/L. The kinetics fitting was consistent with the pseudo-second-kinetic model, which indicated that the main process of HAP adsorption of Pb²⁺ was mainly controlled by surface reactions and chemical reactions. The adsorption isotherms had a satisfactory fit with the Langmuir model, which indicated that the adsorption of Pb²⁺ by HAP was a monolayer adsorption. According to the experimental results, ion exchange, phosphorus supply, precipitate, and complexation are the main immobilization mechanisms for soil remediation with HAP. In remediation of Pb²⁺-contaminated soil experiments, the adsorption rate of Pb²⁺ by HAP was significantly higher than that of non-HAP soil with increasing immobilization days. With the increasing addition of HAP, the weak acid soluble (WA), reducible (RED), oxidizable (OX), and water soluble (WS) are transformed into residue (RES). The application of HAP in contaminated soil effectively reduced the leachable and exchangeable Pb²⁺, indicating that HAP is a potential material for remediating environmental pollution with Pb²⁺.

Removal of chromium (VI) from water by porous carbon derived from corn straw: Influencing factors, regeneration and mechanism

Porous carbon is one of the most widely used materials to remove Cr(VI) from polluted water. Here we reported one efficient porous carbon material prepared from corn straw. The results of Fourier transform infrared spectroscopy (FTIR), Energy dispersion spectrum (EDS), and X-ray photoelectron spectroscopy (XPS) indicated that the porous carbon surface had functional groups such as COOH, OH and COC, etc, which could be acted as active sites during the adsorption process. Brunauer-Emmett-Teller (BET) results showed that the surface area and total pore volume of the adsorbent were 2131.181 m²/g and 1.128 cm³/g, respectively. The percentages of micropore surface area and micropore volume achieved 91.93% and 80.43%, respectively. The maximum adsorption capacity of Cr(VI) was 175.44 mg/g at 25 °C with the well-developed microporous structure and abundant oxygen-containing functional groups of porous carbon. The adsorption process was well described by the pseudo-second order model and Langmuir adsorption isotherm model. It was mainly based on chemical adsorption of a single molecular layer, accompanied by ion exchange reaction, Cr(VI) reduction, and complexation, etc. The adsorbent exhibited excellent removal performance of Cr(VI) in the co-existing ions wastewater and electroplating wastewater, and could remain high removal performance for four adsorption-desorption cycles.