Magnetic bionanoparticles of Penicillium sp. yz11-22N2 doped with Fe3O4 and encapsulated within PVA-SA gel beads for atrazine removal

Gum Ghatti: A Comprehensive Review on Production, Processing, Remarkable Properties, and Diverse Applications

Gum ghatti, popularly known as Indian gum and obtained from Anogeissus latifolia, is a complex high-molecular-weight, water-soluble, and swellable nonstarch polysaccharide comprised of magnesium and calcium salts of ghattic acids and multiple monosugars. Unlike other nontimber forest produce, gums ghatti is a low-volume but high-value product. It has several applications and is widely used as food, in pharmaceuticals, and for wastewater treatment and hydrogel formation, and it has attracted a great deal of attention in the fields of energy, environmental science, and nanotechnology. Industrial applications of gum ghatti are primarily due to its excellent emulsification, stabilization, thickening, heat tolerance, pH stability, carrier, and biodegradable properties. However, utilization of gum ghatti is poorly explored and implemented due to a lack of knowledge of its production, processing, and properties. Nevertheless, there has been interest among investigators in recent times for exploring its production, processing, molecular skeleton, and functional properties. This present review focuses on production scenarios, processing aspects, structural and functional properties, and potential applications in the food, pharmaceuticals, nonfood, and other indigenous and industrial usages.

Coupling of polyhydroxybutyrate and zero-valent iron for enhanced treatment of nitrate pollution within the Permeable Reactive Barrier and its downgradient aquifer

Permeable Reactive Barriers (PRBs) have been utilized for mitigating nitrate pollution in groundwater systems through the use of solid carbon and iron fillers that release diverse nutrients to enhance denitrification efficiency. We conduct laboratory column tests to evaluate the effectiveness of PRBs in remediating nitrate pollution both within the PRB and in the downgradient aquifer. We use an iron-carbon hydrogel (ICH) as PRB filler, which has different weight ratios of polyhydroxybutyrate (PHB) and microscale zero-valent iron (mZVI). Results reveal that denitrification in the downgradient aquifer accounts for at least 19.5 % to 32.5 % of the total nitrate removal. In the ICH, a higher ratio of PHB to mZVI leads to higher contribution of the downgradient aquifer to nitrate removal, while a lower ratio results in smaller contribution. Microbial community analysis further reveals that heterotrophic and mixotrophic bacteria dominate in the downgradient aquifer of the PRB, and their relative abundance increases with a higher ratio of PHB to mZVI in the ICH. Within the PRB, autotrophic and iron-reducing bacteria are more prevalent, and their abundance increases as the ratio of PHB to mZVI in the ICH decreases. These findings emphasize the downgradient aquifer's substantial role in nitrate removal, particularly driven by dissolved organic carbon provided by PHB. This research holds significant implications for nutrient waste management, including the prevention of secondary pollution, and the development of cost-effective PRBs.

Synthesis and characterization of bio-nanocomposite based on chitosan and CaCO3 nanoparticles for heavy metals removal

Water is a vital component of life; therefore, it is critical to have access to pure water for various life-sustaining activities including agriculture and human consumption. An eco-friendly nanocomposite based on chitosan (Cs) and nanomaterials (CaCO3-NPs) were combined to amalgamate the advantages of biopolymers and nanomaterials to overcome the problems of instability, poor mechanical properties, and low removal percentage of biopolymers. The as-prepared samples were characterized and were used for the removal of heavy metal from wastewater. X-ray diffractometer, Fourier transform infrared spectroscopy, and transmission electron microscope were used to distinguish the prepared absorbents. The absorption of the heavy metals by as-prepared samples was examined at different conditions. The kinetic and isotherm models of the adsorption process were also studied. The data showed that the removal percentages of Cd, Cu, Pb, Zn, Cr and Ni by the composite were 98.0, 94.8, 99.0, 97.9, 97.4 and 98.3 %, respectively. The kinetic and isothermal studies showed that the absorption of these metal ions by the samples obeyed a pseudo-second-order mechanism and Langmuir isotherm model, respectively. In addition, the maximum adsorption capacities of Cd, Cu, Pb, Zn, Cr, and Ni ions by as-prepared nanocomposite were 83.33, 47.84, 98.03, 89.28, 62.11, and 63.69 mg/g, respectively.

Effects of released organic components of solid carbon sources on denitrification performance and the related mechanism

Here, a hybrid scaffold of polyvinyl alcohol/sodium alginate (PVA/SA) was used to prepare solid carbon sources (SCSs) for treating low carbon/nitrogen wastewater. The four SCSs were divided into two groups, biodegradable polymers group (including polyvinyl alcohol-sodium alginate (PS) and PS-PHBV (PP), and blended SCSs (PS-PHBV-wood chips (PPW) and PS-PHBV-wheat straw (PPS)). After the leaching experiments, no changes occurred in elemental composition and functional groups of the SCSs, and the released dissolved organic matter showed a lower degree of humification and higher content of labile molecules in the blended SCSs groups using EEM and FT-ICR-MS. The denitrification performance of the blended SCSs was higher, with nitrate removal efficiency over 84%. High-throughput sequencing confirmed PPW had the highest alpha-diversity, and the microbial community structure significantly varied among SCSs. Results of functional enzymes and genes show the released carbon components directly affect the NADH level and electron transfer efficiency, ultimately influencing denitrification performance.

Microbiology and Biochemistry of Pesticides Biodegradation

Pesticides are chemicals used in agriculture, forestry, and, to some extent, public health. As effective as they can be, due to the limited biodegradability and toxicity of some of them, they can also have negative environmental and health impacts. Pesticide biodegradation is important because it can help mitigate the negative effects of pesticides. Many types of microorganisms, including bacteria, fungi, and algae, can degrade pesticides; microorganisms are able to bioremediate pesticides using diverse metabolic pathways where enzymatic degradation plays a crucial role in achieving chemical transformation of the pesticides. The growing concern about the environmental and health impacts of pesticides is pushing the industry of these products to develop more sustainable alternatives, such as high biodegradable chemicals. The degradative properties of microorganisms could be fully exploited using the advances in genetic engineering and biotechnology, paving the way for more effective bioremediation strategies, new technologies, and novel applications. The purpose of the current review is to discuss the microorganisms that have demonstrated their capacity to degrade pesticides and those categorized by the World Health Organization as important for the impact they may have on human health. A comprehensive list of microorganisms is presented, and some metabolic pathways and enzymes for pesticide degradation and the genetics behind this process are discussed. Due to the high number of microorganisms known to be capable of degrading pesticides and the low number of metabolic pathways that are fully described for this purpose, more research must be conducted in this field, and more enzymes and genes are yet to be discovered with the possibility of finding more efficient metabolic pathways for pesticide biodegradation.

Advances in electrospun materials for the adsorption and separation of environmental pollutants: A comprehensive review

Despite a broad range of new techniques developed, adsorption methods remain one of the technologies of choice for the removal of contaminants. However, significant progress has also been made in these, which finds reflection in a new spectrum of adsorbents that can be used. This comprehensive review discusses properties, advantages, and perspectives on the use of custom-made electrospun adsorbents in the processes of heavy metals, agrochemicals, and microplastic contaminants removal from the environment. It presents the versatility and adaptability of materials that can be used as electrospun fibers matrix, also considering the mechanism and parameters of the sorption process carried out with them. The presented review proves, that due to the use of new, custom-made sorbents, such as electrospun materials, the adsorption processes still possess great application potential and development opportunities to provide an attractive and effective alternative to other remediation techniques.

Preparation and performance of bionanocomposites based on grafted chitosan, GO and TiO2-NPs for removal of lead ions and basic-red 46

Wastewater rich in heavy metals and organic compounds represents one of the essential environmental pollutants. Therefore, a practical approach is to fabricate eco-friendly polymer-based systems with a high ability to absorb pollutants. Herein, bionanocomposites consisting of chitosan (Cs) grafted by various monomers, such as acrylamide (Am), acrylic acid (AA), and 4-styrene sulfonic acid (SSA), and hybrid nanoparticles of graphene oxide/titanium dioxide nanoparticles (GO@TiO₂-NPs) were fabricated. The prepared nanomaterials and bionanocomposites characterized via various tools. The data illustrated that the prepared GO had a thickness of 10 nm and TiO₂-NPs had a diameter of 25 nm. In addition, the grafted chitosan (gCs) using Am and SSA had the largest surface area (gCs2; 22.89 nm) and its bionanocomposite (NC5; 104.79 nm). In addition, the sorption ability of the 0.15 g of prepared bionanocomposites to the (100 mg/L) of lead ions (Pb²⁺) and (25 mg/L) of basic-red 46 (BR46) under various conditions has been studied. The results showed that gCs3 and NC5 had the highest adsorption of Pb²⁺ (79.54 %) and BR46 (79.98 %), respectively. The kinetic study results of the sorbents obeyed the Pseudo second-order model. In contrast, the isothermal study followed the Freundlich adsorption model for Pb²⁺ and the Langmuir adsorption model for BR46.

Functional Bimetal/Carbon Composites Co/Zr@AC for Pesticide Atrazine Removal from Water

Atrazine is a toxic and refractory herbicide that poses threats to human health and the ecological environment. In order to efficiently remove atrazine from water, a novel material, Co/Zr@AC, was developed. This novel material is prepared by loading two metal elements, cobalt and zirconium, onto activated carbon (AC) through solution impregnation and high-temperature calcination. The morphology and structure of the modified material were characterized, and its ability to remove atrazine was evaluated. The results showed that Co/Zr@AC had a large specific surface area and formed new adsorption functional groups when the mass fraction ratio of Co²⁺:Zr⁴⁺ in the impregnating solution was 1:2, the immersion time was 5.0 h, the calcination temperature was 500 °C, and the calcination time was 4.0 h. During the adsorption experiment on 10 mg/L atrazine, the maximum adsorption capacity of Co/Zr@AC was shown to be 112.75 mg/g and the maximum removal rate was shown to be 97.5% after 90 min of the reaction at a solution pH of 4.0, temperature of 25 °C, and Co/Zr@AC concentration of 60.0 mg/L. In the kinetic study, the adsorption followed the pseudo-second-order kinetic model (R² = 0.999). The fitting effects of Langmuir and Freundlich isotherms were excellent, indicating that the process of Co/Zr@AC adsorbing atrazine also conformed to two isotherm models, so the adsorption of atrazine by Co/Zr@AC had multiple effects including chemical adsorption, mono-molecular layer adsorption, and multi-molecular layer adsorption. After five experimental cycles, the atrazine removal rate was 93.9%, indicating that Co/Zr@AC is stable in water and is an excellent novel material that can be used repeatedly.

Immobilization of bacterial mixture of Klebsiella variicola FH-1 and Arthrobacter sp. NJ-1 enhances the bioremediation of atrazine-polluted soil environments

In this study, the effects of the immobilized bacterial mixture (IM-FN) of Arthrobacter sp. NJ-1 and Klebsiella variicola strain FH-1 using sodium alginate-CaCl2 on the degradation of atrazine were investigated. The results showed that the optimal ratio of three types of carrier materials (i.e., rice straw powder, rice husk, and wheat bran) was 1:1:1 with the highest adsorption capacity for atrazine (i.e., 3774.47 mg/kg) obtained at 30°C. On day 9, the degradation efficiency of atrazine (50 mg/L) reached 98.23% with cell concentration of 1.6 × 108  cfu/ml at pH 9 and 30°C. The Box-Behnken method was used to further optimize the culture conditions for the degradation of atrazine by the immobilized bacterial mixture. The IM-FN could be reused for 2-3 times with the degradation efficiency of atrazine maintained at 73.0% after being stored for 80 days at 25°C. The population dynamics of IM-FN was explored with the total soil DNA samples specifically analyzed by real-time PCR. In 7 days, the copy numbers of both PydC and estD genes in the IM-FN were significantly higher than those of bacterial suspensions in the soil. Compared with bacterial suspensions, the IM-FN significantly accelerated the degradation of atrazine (20 mg/kg) in soil with the half-life shortened from 19.80 to 7.96 days. The plant heights of two atrazine-sensitive crops (wheat and soybean) were increased by 14.99 and 64.74%, respectively, in the soil restored by immobilized bacterial mixture, indicating that the IM-FN significantly reduced the phytotoxicity of atrazine on the plants. Our study evidently demonstrated that the IM-FN could significantly increase the degradation of atrazine, providing a potentially effective bioremediation technique for the treatment of atrazine-polluted soil environment and providing experimental support for the wide application of immobilized microorganism technology in agriculture.

Toxicological effects, environmental behaviors and remediation technologies of herbicide atrazine in soil and sediment: A comprehensive review

Atrazine has become one of the most popular applied triazine herbicides in the world due to its high herbicidal efficiency and low price. With its large-dosage and long-term use on a global scale, atrazine can cause widespread and persistent contamination of soil and sediment. This review systematically evaluates the toxicological effects, environmental risks, environmental behaviors (adsorption, transport and transformation, and bioaccumulation) of atrazine, and the remediation technologies of atrazine-contaminated soil and sediment. For the adsorption behavior of atrazine on soil and sediment, the organic matter content plays an extremely important role in the adsorption process. Various models and equations such as the multi-media fugacity model and solute transport model are used to analyze the migration and transformation process of atrazine in soil and sediment. It is worth noting that certain transformation products of atrazine in the environment even have stronger toxicity and mobility than its parent. Among various remediation technologies, the combination of microbial remediation and phytoremediation for atrazine-contaminated soil and sediment has wide application prospects. Although other remediation technologies such as advanced oxidation processes (AOPs) can also efficiently remove atrazine from soil, some potential problems still need to be further clarified. Finally, some related challenges and prospects are proposed.

Immobilization of Biomass Materials for Removal of Refractory Organic Pollutants from Wastewater

In the field of environmental science and engineering, microorganisms, enzymes and algae are promising biomass materials that can effectively degrade pollutants. However, problems such as poor environmental adaptability, recycling difficulties, and secondary pollution exist in the practical application of non-immobilized biomass materials. Biomass immobilization is a novel environmental remediation technology that can effectively solve these problems. Compared with non-immobilized biomass, immobilized biomass materials have the advantages of reusability and stability in terms of pH, temperature, handling, and storage. Many researchers have studied immobilization technology (i.e., methods, carriers, and biomass types) and its applications for removing refractory organic pollutants. Based on this, this paper reviews biomass immobilization technology, outlines the mechanisms and factors affecting the removal of refractory organic pollutants, and introduces the application of immobilized biomass materials as fillers for reactors in water purification. This review provides some practical references for the preparation and application of immobilized biomass materials and promotes further research and development to expand the application range of this material for water purification.

Construction of Magnetic Composite Bacterial Carrier and Application in 17β-Estradiol Degradation

Estrogen contamination is widespread and microbial degradation is a promising removal method; however, unfavorable environments can hinder microbial function. In this study, a natural estrogen 17β-estradiol (E2) was introduced as a degradation target, and a new combination of bacterial carrier was investigated. We found the best combination of polyvinyl alcohol (PVA) and sodium alginate (SA) was 4% total concentration, PVA:SA = 5:5, with nano-Fe3O4 at 2%, and maltose and glycine added to promote degradation, for which the optimal concentrations were 5 g·L−1 and 10 g·L−1, respectively. Based on the above exploration, the bacterial carrier was made, and the degradation efficiency of the immobilized bacteria reached 92.3% in 5 days. The immobilized bacteria were reused for three cycles, and the degradation efficiency of each round could exceed 94%. Immobilization showed advantages at pH 5, pH 11, 10 °C, 40 °C, and 40 g·L−1 NaCl, and the degradation efficiency of the immobilized bacteria was higher than 90%. In the wastewater, the immobilized bacteria could degrade E2 to about 1 mg·L−1 on the 5th day. This study constructed a bacterial immobilization carrier using a new combination, explored the application potential of the carrier, and provided a new choice of bacterial immobilization carrier.

Kinetic and statistical perspectives on the interactive effects of recalcitrant polyaromatic and sulfur heterocyclic compounds and in-vitro nanobioremediation of oily marine sediment at microcosm level

A halotolerant biosurfactant producer Pseudomonas aeruginosa strain NSH3 (NCBI Gene Bank Accession No. MN149622) was isolated to degrade high concentrations of recalcitrant polyaromatic hydrocarbons (PAHs) and polyaromatic heterocyclic sulfur compounds (PASHs). In biphasic batch bioreactors, the biodegradation and biosurfactant-production activities of NSH3 have been significantly enhanced (p < 0.0001) by its decoration with eco-friendly prepared magnetite nanoparticles (MNPs). On an artificially contaminated sediment microcosm level, regression modeling and statistical analysis based on a 2³ full factorial design of experiments were trendily applied to provide insights into the interactive impacts of such pollutants. MNPs-coated NSH3 were also innovatively applied for nanobioremediation (NBR) of in-vitro diesel oil-polluted sediment microcosms. Gravimetric, chromatographic, and microbial respiratory analyses proved the significantly enhanced biodegradation capabilities of MNPs-coated NSH3 (p < 0.001) and the complete mineralization of various recalcitrant diesel oil components. Kinetic analyses showed that the biodegradation of iso- and n-alkanes was best fitted with a second-order kinetic model equation. Nevertheless, PAHs and PASHs in biphasic batch bioreactors and sediment microcosms followed the first-order kinetic model equation. Sustainable NBR overcome the toxicity of low molecular weight hydrocarbons, mass transfer limitation, and steric hindrance of hydrophobic recalcitrant high molecular weight hydrocarbons and alkylated polyaromatic compounds.

Encapsulation of Bacillus pumilus G5 from polyvinyl alcohol‑sodium alginate (PVA-SA) and its implications in improving plant growth and soil fertility under drought and salt soil conditions

Drought and salt stresses adversely affect the growth and yield of plants in agricultural production. Bacillus pumilus, an important plant growth-promoting bacterium, play a significant role in improving plant tolerance to abiotic stresses. In this study, B. pumilus G5 were immobilized in polyvinyl alcohol‑sodium alginate (PVA-SA) microbeads and then applied on the Pharbitis nil under drought and salt stresses by pot experiment. Orthogonal array experiments showed that the optimal immobilization conditions of PVA-SA immobilized G5 microbeads were adsorbent 6.0%, PVA: SA 1:1 (3.0%), CaCl₂ 4.0%, and bacterium: embedding agent (PVA-SA) 3:4; And the G5 microbeads produced at the optimal condition exhibited better cultivable bacteria count, encapsulation rate, expansion rate and mechanical strength. Pot experiment showed that G5 microbeads significantly increased the length and diameter of root and stem, and dry weight of P. nil during experimental stage under drought and salt stress. G5 microbeads also increased the total cultivable bacteria population, the activities of invertase (INV), urease (URE), phosphatase (PHO) and catalase (CAT), and the contents of available nitrogen (AN) and available phosphorus (AP) in the rhizosphere soil of P. nil. Therefore, our study obtained the optimal process of G5 microbeads, and confirmed its effect on improved plant growth and soil chemical and biological properties of P. nil. Thus it can be used as sustainable tool for eco-friendly bio-inoculants at salinity soil within arid and semi-arid areas.

Intermediate accumulation and toxicity reduction during the selective photoelectrochemical process of atrazine in complex water bodies

Selective removal of atrazine (ATZ) in wastewater and clarification of the degradation intermediate-toxicity correlation are of great importance. A newly molecularly imprinted, {001} facets-exposed TiO₂ (MI-TiO_2,001) photoanode with strong catalytic and selective ability was designed. ATZ was selectively removed from pesticide wastewater, reaching 1.9 µg L^-1, approximately 1/10 of the concentration achieved with nonselective treatment. This selective removal originated from the preferential adsorption and enrichment of ATZ onto MI-TiO_2,001. The highly specific recognition relied on the halogen bond and strong hydrogen bond formed between the Cl atom and triazine ring π orbital of ATZ and the surface -OH group of MI-TiO_2,001 as well as the recognition of MI-TiO_2,001 to the shape and size of ATZ. The specific interaction leads to different accumulations of intermediates. The correlation of intermediate and toxicity was also discussed. Aquatic toxicity was rapidly reduced through the direct dealkylation path, and due to the accumulation of highly toxic 2‑hydroxy-4-ethylamino-6-isopropylamino-s-triazine, there will be transient fluctuations via the dechlorination-hydroxylation path first. The final product was identified as nearly nontoxic cyanuric acid, the selective accumulation of which indicated that there was almost 100% removal of aquatic toxicity and cytotoxicity with only 9.8% removal of total organic carbon. This work provides new insight into the correlation of pollutant degradation intermediates and changes in toxicity.

Enhanced removal of trivalent chromium from leather wastewater using engineered bacteria immobilized on magnetic pellets

Leather wastewater contains various toxic contaminants, with trivalent chromium (Cr(III)) having high concentration and adversely affecting wastewater treatment. In this study, a Cr(III) adsorption protein (MerP) was displayed on the cell surface of Escherichia coli and then coupled with a magnetic pellet system to facilitate Cr(III) adsorption. The results showed the engineered strain M-BL21 achieved an in vitro Cr(III) adsorption capacity of 2.38 mmol/g. Next, the magnetic pellets were prepared as component ratios of sodium alginate (2.5%), polyvinyl alcohol (8%), Fe₃O₄ nanoparticles (3.5%), and M-BL21 at 3 g/L. The optimized system was capable of Cr(III) adsorption at an efficiency of 91.29%, which was substantially higher than that of the magnetic carrier alone (67%). Results of scanning electron microscopy with energy-dispersive X-ray analysis proved that Cr(III) was absorbed on the magnetic pellet. The recyclable performance of magnetic property (13.34185 emu/g) and high Cr(III) adsorption efficiency (68.75%) remained after five cycles of Cr(III) absorption. In the medium-scale experiment, 25 L of leather wastewater were treated with magnetic pellet and the Cr(III) removal efficiency reached 88.2%. Thus, our results present an advanced, fully operational, and eco-friendly method for in situ removal of Cr(III) from contaminated wastewater.

Enhancing anammox resistance to low operating temperatures with the use of PVA gel beads

Low temperatures, or a sudden decrease in operating temperature, can seriously inhibit anammox activity, it is, therefore, important to maintain anammox activities at a low temperature. In this study, the use of gel beads to enhance the resistance of anammox biomass to a low temperature was investigated. The performance of three reactors: R1 without gel beads; R2 with polyvinyl alcohol/chitosan (PVA/CS); R3 with PVA/CS/Fe, was studied and compared in a temperature transition from 35 to 8 °C. When the operating temperature was ≥25 °C, there was little difference in nitrogen removal among the three reactors. Decreasing the temperature to < 25 °C created obvious difference between R1 and R2/R3. R1 had a nitrogen removal efficiency (NRE) of 33.1 ± 25.3% at 10 °C, significantly lower than that of R2 (90.5 ± 2.5%) or R3 (87.7 ± 11.1%). Unclassified Candidatus Brocadiaceae was the dominant genus at 10 °C, with an abundance of 44.4, 56.5 and 58.7% in R1, R2 and R3, respectively. These differences were attributed to the use of gel beads, which promoted the granulation of both the non-immobilized sludge and the immobilized biomass, resulting in higher anammox activities in R2/R3. The non-immobilized sludge of R1 was dominated by small particles (<300 μm) at 10 °C, while in R2 and R3 large particles (1000-2000 μm) were the main components. Furthermore, the immobilized biomass on gel beads exhibited much higher anammox activity and maintained a relatively high level of nitrate reductase and nitrite reductase in response to the temperature decrease. The Fe²⁺/Fe³⁺ in the PVA/CS/Fe gel beads further promoted microbial aggregation and led to an improved performance in R3 compared to R2. The results of this study demonstrate an effective approach to increase anammox resistance at low operating temperatures.

Rapid uptake of atrazine from aqueous phase by thermally activated MCM-41

This study was designed to prepare an adsorbent without any complex modification process for the removal of atrazine (AZN) from aqueous phase. Thus, Mobil composition of matter No. 41 (MCM-41) was synthesized and modified by physical activation at high temperature (650 °C). The synthesized adsorbent was tested by XRD, SEM, EDX, FT-IR and BET to confirm the successful synthesis as well as effectiveness for the adsorption of AZN. The average particle size of prepared material was found to be about 500 nm, while the BET calculations showed that adsorbent was porous with a specific surface area of 25.9 m²/g. Later, it was used in batch removal studies of AZN for which, it showed a high adsorption capacity of 89.99 (mg/g). The pH of 6, temperature of 313 K was found to be the optimized conditions for the maximum removal of AZN. Of the four kinetic models studied, the pseudo-first-order yielded a superior fit in comparison with the other three models. The results indicated that the five linearized adsorption equilibrium isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Harkins-Jura models) closely correlate the AZN adsorption removal process with Pearson correlation coefficient (R²) values of 0.9955, 0.8551, 0.8736, 0.8913 and 0.7253, respectively. The energy functions obtained by thermodynamic analysis suggested that the AZN sorption follows a non-spontaneous and endothermic path.

Preparation, Performances and Mechanisms of Co@AC Composite for Herbicide Atrazine Removal in Water

In this study, a high-performance adsorbent Co@AC was prepared by loading cobalt ions (Co2+) on activated carbon (AC) via solution impregnation and high-temperature calcination technology, and was used to remove atrazine in water. The preparation factors on the adsorbent properties were studied, and the characteristics were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrometer (FTIR). The results showed that Co@AC possessed the best performance when the factors were 7.0% of Co2+ (w/v), 7.0 h of immersing time, 500 °C of calcination temperature and 4.0 h of calcination time. The adsorption conditions and mechanisms for atrazine removal by Co@AC were also studied scientifically. As the conditions were pH 4.0, reaction time 90 min and temperature 25 °C, Co@AC had the largest adsorption capacity, which was 92.95 mg/g, and the maximum removal rate reached 94.79%. The correlation coefficient of the Freundlich isotherm was better than that of the Langmuir isotherm, and the adsorption process followed the pseudo-second-order kinetic model. Cycle experiments showed that the removal efficiency of atrazine by Co@AC remained above 85% after five repeated experiments, indicating that Co@AC showed a strong stable performance and is a promising material for pesticides removal.

Optimization, equilibrium, adsorption behavior and role of surface functional groups on graphene oxide-based nanocomposite towards diclofenac drug

Aquatic contamination of diclofenac (DCF), an emergent non-steroidal anti-inflammatory drug (NSAIDs), can result in adverse effects to many ecosystems through biomagnification. Hence, introducing effective remediation techniques to sequester the pharmaceutical wastes is highly fundamental to prevent their accumulation in the environment. Generally, adsorption has been presented as a green and efficient approach. Herein, we report the characterization and application of the novel magnetic nanocomposite (GO@CoFe₂O₄) derived from cobalt-based ferrite (CoFe₂O₄) and graphene oxide (GO) for DCF adsorption. For the optimization procedure, the response surface methodology (RSM) was adopted to investigate the impacts of DCF concentration (1.6-18.4 mg/L), DCF dosage (0.08-0.92 g/L), and solution pH (2.6-9.4) to find the optimum conditions for DCF removal, at 10.5 mg/L, 0.74 g/L, and pH 4, respectively. For the adsorption experiments, the kinetic, isotherm, thermodynamic, and intraparticle diffusion models were systematically studied. Moreover, we have elucidated the role of functional groups on the surface of GO@CoFe₂O₄ in enhancing the adsorption of DCF drug. With good removal efficiency (up to 86.1%), high maximum adsorption capacity (32.4 mg/g), GO@CoFe₂O₄ can be a potential candidate to eliminate DCF drug from water.

Preparation, Performances, and Mechanisms of Microbial Flocculants for Wastewater Treatment

In recent years, close attention has been paid to microbial flocculants because of their advantages, including safety to humans, environmental friendliness, and acceptable removal performances. In this review, the preparation methods of microbial flocculants were first reviewed. Then, the performances of bioflocculants in the removal of suspended solids, heavy metals, and other organic pollutants from various types of wastewater were described and commented, and the removal mechanisms, including adsorption bridging, charge neutralization, chemical reactions, and charge neutrality, were also discussed. The future research needs on microbial flocculants were also proposed. This review would lead to a better understanding of current status, challenges, and corresponding strategies on microbial flocculants and bioflocculation in wastewater treatment.

Enhanced passivation of lead with immobilized phosphate solubilizing bacteria beads loaded with biochar/ nanoscale zero valent iron composite

Phosphate solubilizing bacteria (PSBs) can effectively enhance the stability of lead via the formation of insoluble Pb-phosphate compounds. This research presents a bio-beads, which was implemented with the help of a self-designed porous spheres carrier, by immobilized PSBs strains Leclercia adecarboxylata (hereafter referred as L1-5). In addition, the passivation efficiency of lead via bio-beads under different conditions and its mechanism were also investigated in this study. The results indicated that phosphate solubilized by bio-beads could reach 30 mg/L in Ca₃(PO₄)₂ medium containing 1 mM Pb²⁺, and the highest removal rate of Pb²⁺ in beef peptone liquid medium could reach 93%, which is better than that of free bacteria. Furthermore, it was also concluded that the lead could be transformed into stable crystal texture, such as Pb₅(PO₄)₃Cl and Pb₅(PO₄)₃OH. Both hydrophobic and hydrophilic groups in the bio-beads could capture Pb²⁺, which indicated that electrostatic attraction and ion-exchange were also the mechanism of Pb²⁺ adsorption. All the experimental findings demonstrated that this bio-bead could be consider as an efficient way for the lead immobilization in contaminated soil in the future.

Removal of Congo red from aqueous solution by adsorption using gum ghatti and acrylamide graft copolymer coated with zero valent iron

Gum ghatti (Gg) and acrylamide (AAm) grafted copolymer [poly (Gg-AAm)] coated by zero valent iron (ZVI) was developed to remove toxic Congo red (CR) from waste water. Prepared composite, [poly (Gg-AAm)/ZVI] was characterized by FESEM, TEM, BET, FTIR and XRD. CR adsorption from water using [poly (Gg-AAm)/ZVI] was investigated and several parameters discussed, such as solution pH, contact time, dosage and temperature to find out removal efficiency of polymer composite. The kinetic data for the adsorption of CR followed the pseudo-second-order model and the Langmuir maximum adsorption capacity for CR at pH 7.0 were found to be 153.8, 200 and 250 mg/g at 25, 35 and 45 °C correspondingly. Desorption studies revealed that prepared composite can be used up to three cycles efficiently and thermodynamic parameters such as Gibbs free energy (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) changes showed the adsorption of CR onto [poly (Gg-AAm)/ZVI] was feasible, spontaneous and endothermic.

Magnetite nanoparticle decorated reduced graphene oxide for adsorptive removal of crystal violet and antifungal activities

This work reports the synthesis and application of magnetic rGO/Fe₃O₄ NCs using a pod extract of Dolichos lablab L. as areducing agent. GO was synthesized by a modified Hummers method, however GO was reduced using the plant extract to produce rGO. The as-synthesized rGO/Fe₃O₄ NCs were characterized by UV-vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, FT-Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy supported with energy dispersed X-ray spectroscopy (FESEM-EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The synthesis of magnetic rGO/Fe₃O₄ NCs was confirmed from characterization results of FT-Raman, TEM and VSM. The FT-Raman results showed the D and G bands at 1306.92 cm⁻¹ and 1591 cm⁻¹ due to rGO and a peak at around 589 cm⁻¹ due to Fe₃O₄ NPs that were anchored on rGO sheets; TEM results showed the synthesis of Fe₃O₄ with an average particle size of 8.86 nm anchored on the surface of rGO sheets. The VSM result confirmed the superparamagnetic properties of the rGO/Fe₃O₄ NCs with a saturation magnetization of 42 emu g⁻¹. The adsorption capacity of rGO/Fe₃O₄ NCs towards crystal violet (CV) dye was calculated to be 62 mg g⁻¹. The dye removal behavior fitted well with the Freundlich isotherm and the pseudo-second-order kinetic model implies possible chemisorption. Besides, rGO/Fe₃O₄ NCs showed antifungal activities against Trichophyton mentagrophytes and Candida albicans by agar-well diffusion method with a zone inhibition of 24 mm and 21 mm, respectively. Therefore, rGO/Fe₃O₄ NCs can be used as an excellent adsorbent to remove organic dye pollutants and kill pathogens.

This work reports synthesis of magnetic rGO/Fe₃O₄ NCs using pod extract of Dolichos lablab L. as a reducing agent and its applications.

Bioremediation of gaseous methyl tert-butyl ether by combination of sulfuric acid modified bagasse activated carbon-bone biochar beads and Acinetobacter indicus screened from petroleum contaminated soil

Combination of sulfuric acid modified bagasse activated carbon-bone biochar beads and Acinetobacter indicus screened from petroleum contaminated soil was the best condition for gaseous methyl tert-butyl ether (MTBE) removal. It was found that H₂SO₄ modified bagasse AC in powder form had higher adsorption capacity (989.33 mg g^-1) than that in bead form (1.94 mg g^-1). In addition, bone biochar in powder form (3.51 mg g^-1) also had higher adsorption capacity than that in bead form (1.63 mg g^-1). This was the fact that material beads contained high moisture content that inhibited the penetration of gaseous MTBE into the material. And a mixed material of H₂SO₄ modified bagasse AC-bone biochar beads had the highest adsorption capacity (2.22 mg g^-1) compared to individual H₂SO₄ modified bagasse AC beads (1.94 mg g^-1) and bone biochar beads (1.63 mg g^-1) due to a mixed material had more rough surface and high surface area on its material. So, gaseous MTBE can penetrate through this material more easily. Although the maximum adsorption capacity of H₂SO₄ modified bagasse AC in powder form was the highest but microorganism cannot sustain and survive in this form for a long time. Therefore, the material beads were more suitable for microorganism to grow and degrade gaseous MTBE. Microorganism can degrade MTBE and caused no secondary wastes. Moreover, A. indicus was a novel strain for MTBE removal that has not been previously reported. Therefore, a combination of A. indicus-mixed material beads was a good choice for MTBE removal in a biofilter system.

Efficient total nitrogen removal from wastewater by Paracoccus denitrificans DYTN-1

Bioaugmentation is an effective treatment method to reduce nitrogenous pollutants from wastewater. A strain of DYTN-1, which could effectively remove TN from sewage, was isolated from the sludge of a wastewater treatment plant and was identified as Paracoccus denitrificans. The TN in wastewater reduced to <20 mg l^-1 within 12 h under optimal conditions by free cells of P. denitrificans DYTN-1. To enhance the removal of TN, P. denitrificans DYTN-1 cells were immobilized in sodium alginate (SA) using different divalent metal ions as cross-linking agents. It was found that the immobilized P. denitrificans DYTN-1 cells could reduce the TN concentration from 100 to below 20 mg l^-1 within 8 h. After the optimization of an orthogonal experiment, the immobilized P. denitrificans DYTN-1 cells could reduce the TN concentration from 100 mg l^-1 to below 20 mg l^-1 within 1 h and significantly reduce the fermentation cycle. These findings would provide an economical and effective method for the removal of total nitrogen in wastewater by immobilized cells of P. denitrificans DYTN-1. SIGNIFICANCE AND IMPACT OF THE STUDY: We identified a new Paracoccus denitrificans strain (DYTN-1) for removal of the total nitrogen in wastewater. The total nitrogen could be removed effectively by P. denitrificans DYTN-1 within 12 h in wastewater. Using sodium alginate as the carrier and Ba²⁺ as cross-linking agent, the immobilized P. denitrificans DYTN-1 cells could improve the removal efficiency of total nitrogen in wastewater and significantly reduce the fermentation cycle. The assay has provided an economical and effective method for the removal of total nitrogen in wastewater by immobilized cell.

A Review on Recent Treatment Technology for Herbicide Atrazine in Contaminated Environment

Atrazine is a kind of triazine herbicide that is widely used for weed control due to its good weeding effect and low price. The study of atrazine removal from the environment is of great significance due to the stable structure, difficult degradation, long residence time in environment, and toxicity on the organism and human beings. Therefore, a number of processing technologies are developed and widely employed for atrazine degradation, such as adsorption, photochemical catalysis, biodegradation, etc. In this article, with our previous research work, the progresses of researches about the treatment technology of atrazine are systematically reviewed, which includes the four main aspects of physicochemical, chemical, biological, and material-microbial-integrated aspects. The advantages and disadvantages of various methods are summarized and the degradation mechanisms are also evaluated. Specially, recent advanced technologies, both plant-microbial remediation and the material-microbial-integrated method, have been highlighted on atrazine degradation. Among them, the plant-microbial remediation is based on the combined system of soil-plant-microbes, and the material-microbial-integrated method is based on the synergistic effect of materials and microorganisms. Additionally, future research needs to focus on the excellent removal effect and low environmental impact of functional materials, and the coordination processing of two or more technologies for atrazine removal is also highlighted.

Enhanced activation of peroxymonosulfte by LaFeO3 perovskite supported on Al2O3 for degradation of organic pollutants

In this study, the effect of various supports on activation of peroxymonosulfate and consequent degradation of Acid Orange 7 (AO7) in aqueous solutions was examined at the presence of LaFeO₃ perovskite as catalyst. Results showed that the AO7 degradation efficiency by LaFeO₃ supported on different supports was in an order of LaFeO₃/Al₂O₃ (86.2%) > LaFeO₃ (70.8%) > LaFeO₃/CeO₂ (59.0%) > LaFeO₃/SiO₂ (52.3%) > LaFeO₃/TiO₂ (32.2%). Moreover, the pseudo first-order rate constant for AO7 degradation by LaFeO₃/Al₂O₃ was 3.2 times than that by LaFeO₃. The enhancement was attributed to its large surface area, abundant chemisorbed surface-active oxygen, redox property and faster electron transfer. AO7 degradation and the leaching of iron ions decreased with the increase of pH. Data of electron spin resonance spectroscopy and quenching experiments revealed that sulfate and hydroxyl radicals were generated on LaFeO₃/Al₂O₃ surface, while sulfate radicals were identified to be the main reactive species responsible for AO7 degradation. Mechanisms for peroxymonosulfate activation were consequently proposed. Furthermore, LaFeO₃/Al₂O₃ catalyst exhibited a superior stability after five cycles. This work provides a new approach for design of iron-based perovskite catalysts with high and stable catalytic activity for removal of organic pollutants from aqueous solutions.

NanoFe3O4 accelerates anoxic biodegradation of 3, 5, 6-trichloro-2-pyridinol

3, 5, 6-trichloro-2-pyridinol (TCP) is a widespread organic pollutant with persistent, mobile and high antimicrobial effects. Here, nanoFe₃O₄ was firstly introduced into the anoxic biodegradation of TCP. It was found that nanoFe₃O₄ significantly accelerated TCP biodegradation. The removal rate of TCP (100 mg L^-1) increased from 83.03% to 98.74% within 12 h in the presence of nanoFe₃O₄, and the addition of nanoFe₃O₄ also promoted the accumulation of CO₂. Reductive dechlorination mechanism was involved in anoxic biodegradation of TCP. Molecular approaches further revealed that nanoFe₃O₄ distinctly induced the shifts of bacterial community. The dominant genus Ochrobactrum was converted to genus Delftia in nanoFe₃O₄ treatment, and the relative abundance of Delftia increased from 10.26% to 44.62%. Meanwhile, the total relative abundance of bacteria related to TCP dechlorination and degradation significantly increased in the presence of nanoFe₃O₄. These results indicated that nanoFe₃O₄ induced the enrichment of TCP-degrading bacteria to promote the anoxic biodegradation of TCP.

Biological denitrification using polycaprolactone-peanut shell as slow-release carbon source treating drainage of municipal WWTP

The development of slow-release carbon source is an effective way to reduce the total nitrogen (TN) in low carbon to nitrogen ratio wastewater. In this study, a novel solid slow-release carbon source (PPP) was prepared using polycaprolactone (PCL) and peanut shell (PS) as carbon sources with polyvinyl alcohol-sodium alginate (PVA-SA) as hybrid scaffolds. The carbon release properties of PPP and each carbon source materials were compared. The performances of nitrogen removal and microbial community structure using PPP as external carbon source were investigated. The results showed that PPP had the best slow-release performance, and its release process followed the first-order release equation. The ratio of acetic acid, propionic acid and butyric acid in released organic matter was stable at (75.73 ± 4.62)%:(17.22 ± 4.53)%:(7.06 ± 1.02)%. When using PPP as an external carbon source for denitrification, the relative abundance of Gammaproteobacteria increased from 39.32% to 46.66%, while the Shannon index decreased from 8.59 to 8.29. The utilization efficiency of PPP was determined by the ratio of the organic matter releasing rate to the released organic matter consumption rate. By optimizing the PPP dosage, both high nitrogen removal efficiency and low residual organic matter could be achieved.

Shape stable poly(vinyl alcohol) hydrogels with immobilized activated sludge at repeated dry-rewet cycles

The poly(vinyl alcohol) (PVA) hydrogels can be used as a non-toxic and inexpensive immobilization matrix for microbial cells with capability of degrading organic or inorganic pollutants in wastewaters. This study for the first time produced the PVA hydrogels with immobilized cells by two-stage crosslinking which have high shape stability at dry-rewet cycles and, when recovered after sequentially three 24-hr cultivations, reveal high bioactivity in wastewater treatment. The [B(OH)₃][SO₄^2-] cores inside the PVA-boric acid-sulfate hydrogels are proposed to support the immobilized cells with sufficient structure flexibility and strength to maintain hydrogel structural integrity and of sufficient recalcitrance to biological attack. Conversely, neither the PVA-boric acid hydrogels nor the PVA-borate hydrogels can be applied as organic pollutant degraders with dry storage capability. The PVA-boric acid-sulfate hydrogels are proposed as ideal matrix that can be produced and stored in dry, massive quantity and then applied latter at the same or different sites.

Atrazine degradation using Fe3O4-sepiolite catalyzed persulfate: Reactivity, mechanism and stability

In this study, with sepiolite as a support, a novel magnetic Fe₃O₄-sepiolite composite was fabricated by coprecipitation method. The characterization results reveal that the sepiolite support could anchor Fe₃O₄ nanoparticles with good dispersion. The composite was used as a catalyst to activate persulfate (PS) for atrazine (ATZ) degradation. 71.6% of ATZ and 20.9% of solution TOC could be removed after 60 min with 92 mmol/L of PS ([ATZ]₀ = 10 mmol/L). Due to the good adsorption capacity of Fe₃O₄-sepiolite composite toward ATZ, the degradation was considered to be facilitated by an adsorption process, since the adsorbed ATZ can be more easily transported to the active sites and be degraded in situ. Operation factors, including PS dose and solution pH, were investigated and found to be influential for the ATZ removal. The Fe₃O₄-sepiolite composite maintained its catalytic activity and structural stability with negligible Fe leaching during the recycling batch experiments. The intermediate products were further identified and the possible transformation pathway was then proposed based on the results. The findings of this research promote the application of Fe₃O₄-sepiolite composite as efficient and recyclable heterogeneous catalyst for organic degradation, and provide insights into the development of alternative catalysts with good adsorptive properties.

Biodegradation of Atrazine by the Novel Klebsiella variicola Strain FH-1

Bacterial strain FH-1 with high efficiency of degrading Atrazine is separated by means of enrichment culture from the soil applied with Atrazine for many years. FH-1, recognized as Klebsiella variicola based on phylogenetic analysis of 16S rDNA sequences, can grow with Atrazine which is the sole nitrogen source. In fluid inorganic salt medium, the optimal degradation temperature, pH value, and initial concentration of Atrazine are 25°C, 9.0, and 50 mg L^–1, respectively, and the degradation rate of Atrazine by strain FH-1 reached 81.5% in 11 d of culture. The degrading process conforms to the kinetics equation of pesticide degradation. Among the metal ions tested, Zn²⁺ (0.2 mM) has the most significant effect of facilitation on the degradation of Atrazine. In the fluid medium with Zn²⁺, the degradation rate of Atrazine is increased to 72.5%, while the Cu²⁺ (0.2 mM) inhibits the degradation of Atrazine. The degradation products of Atrazine by strain FH-1 were identified as HEIT (2-hydroxyl-4-ethylamino-6-isopropylamino-1,3,5-triazine), MEET (2-hydroxyl-4,6-bis(ethylamino)-1,3,5-triazine), and AEEO (4,6-bis(ethylamino)-1,3,5-triazin-2(1H)-one) by HPLC-MS/MS. Three genes (atzC, trzN, and trzD) encoding for Atrazine degrading enzymes were identified by PCR and sequencing in strain FH-1. This study provides additional theoretical support for the application of strain FH-1 in bioremediation of fields polluted by Atrazine.

Effects of Ca2+ and fulvic acids on atrazine degradation by nano-TiO2: Performances and mechanisms

In this study, the adsorption and UV photocatalytic degradation of atrazine using nano-TiO₂ particles were studied systematically, and the colloidal stability of nano-TiO₂ particles in solution was also investigated to reveal the removal mechanism. Experiments which contained the first 6.0 hours darkness and 4.0 hours UV illumination later were conducted at different concentrations of Ca²⁺ and/or fulvic acids (FA) at pH = 7.0. Results showed that the adsorption rate of atrazine onto nano-TiO₂ particles decreased with the increase of Ca²⁺ and/or FA concentrations, which could be explained well by the colloidal stability of nanoparticles. When the solution contained Ca²⁺ or Ca²⁺-FA, the nanoparticles were aggregated together leading to the decrease of the contact surface area. Besides, there existed competitive adsorption between FA and atrazine on the particle surface. During photocatalytic degradation, the increase of Ca²⁺ and/or FA concentration accelerated the aggregation of nano-TiO₂ particles and that reduced the degradation efficiency of atrazine. The particle sizes by SEM were in accordance with the aggregation degree of nanoparticles in the solutions. Sedimentation experiments of nano-TiO₂ particles displayed that the fastest sedimentation was happened in the CaCl₂ and FA coexistent system and followed by CaCl₂ alone, and the results well demonstrated the photodegradation efficiency trends of atrazine by nano-TiO₂ particles under the different sedimentation conditions.

The three-dimensional flower-like Bi2WO6 assisted by ethanolamine through a microwave method for efficient photocatalytic activity

The three-dimensional flower-like Bi2WO6 was synthesized through a one-step microwave method (the reaction temperature was 434 K and the reaction took 10 min) with the assistance of ethanolamine (EA). The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, PL, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analysis. Methyl orange was used as target pollutant to evaluate the photocatalysis property of samples. Furthermore, the influence of the mechanism of EA on the structure and catalytic performance of Bi2WO6 was discussed. The detailed characterizations revealed that the three-dimensional flower-like Bi2WO6 was successfully synthesized with the assistance of EA. The results confirmed that EA significantly influenced the morphology of Bi2WO6 products. The addition of EA can effectively alter the pressure of the reaction and improve the crystal phase and structure of Bi2WO6 photocatalysts, enhancing the photocatalytic activity of samples and improving the photocatalytic efficiency. EA can serve as an assembling agent and structure-directing agent resulting in the formation of flower-like architectures. With the increase of the amount of EA, the as-prepared Bi2WO6 sample gradually forms a flower-like structure, leading to a shorter time of light holes migrating to the surface of the catalyst. It makes the compound rate significantly decreased, and improves the photocatalytic efficiency of the sample.

Both cell envelope and cytoplasm were the locations for chromium(VI) reduction by Bacillus sp. M6

Biotreatment is an effective way in remediation of chromium(VI) (Cr(VI)) contamination, but its mechanism and reaction sites are still not clear. Herein, Bacillus sp. M6 was used as a model bacterium in this study to investigate the removal mechanism of Cr(VI) in solution. The results showed that the removal of Cr(VI) was attributed to direct reduction by Bacillus sp. M6, and the reduction locations occurred both on the cell envelope and in the cytoplasm. Meanwhile, bioanalysis of Bacillus sp. M6 by SEM-EDS and TEM-EDS, indicated that Cr(III)-containing precipitates distributed both on the surface and in the cytoplasm of Bacillus sp. In addition, XPS analysis demonstrated that the chromium could be bound to cells by coordination with functional groups (C-based and O-based) on the bacterial surface. This work offers a new and deep insight into the mechanism of Cr(VI) reduction by Bacillus sp.

Application of a novel Mass Bio System to remove low-concentration ammonia nitrogen from water bodies

Water pollution due to ammonia is one of the most serious problems faced by the human beings and other life forms worldwide. With the rapid development of economy, pollution of water resources by ammonium (NH₄⁺) pollutants has increased severely. The water supply system has exceeded its capacity with regard to both quantity and quality of water. Many countries have already established a standard for strict limitation of ammonium nitrogen (NH₄⁺-N) or NH₃ content in drinking water. In this study, a novel Mass Bio System (MBS), a suspended biologically activated carbon granular carrier cubic particle with 2–5 mm side length and a specific gravity of 1.02–1.08, was used for water treatment. In order to find a suitable method for ammonium removal from water resources, synthetic water containing NH₄⁺-N at a concentration of about 10 ppm was treated by MBS. NH₄⁺-N was nitrified to nitrate nitrogen (NO₃⁻-N) by MBS in an inner-circulated fluidized bed reactor continuously. MBS showed an efficient and stable NH₄⁺-N nitrifying performance at temperature of 20–30 °C and DO of 3–4 mg L⁻¹. With an influent concentration of NH₄⁺-N at 10–15 mg L⁻¹, the concentration of effluent NH₄⁺-N and nitrite nitrogen (NO₂⁻-N) was below 0.25 mg L⁻¹, showing an average removal efficiency of above 90% within a hydraulic retention time (HRT) of 30 min. The pH value of effluent water remained at 7.2–7.3 automatically. Removal of load could reach 256.1 mg-N per (L-pellet h) and oxygen uptake rate increased to 1170.9 mg-O₂ per (L-pellet h). The nitrifying process fits to zero-order degradation kinetics. High biomass retention was observed by scanning electron microscopy (SEM).

Removal process of low concentration of ammonia nitrogen (about 10 ppm NH₄⁺-N) by Novel Mass Bio System (MBS).

A facile route to magnetic mesoporous core–shell structured silicas containing covalently bound cyclodextrins for the removal of the antibiotic doxycycline from water

The excessive use of antibiotics has led to various environmental problems; the control and separation of these antibiotics are important in environmental science. Herein, a novel mesoporous nanocomposite, Fe₃O₄@SiO₂@mSiO₂-CD, has been synthesized for the removal of antibiotic compounds from aqueous media. The well-designed nanocomposite is composed of β-cyclodextrin functionalized surfaces, ordered mesoporous silica shells with large radially oriented mesopores, and nonporous silica-coated magnetic cores (Fe₃O₄). The synergistic action of both the mesoporous structure and the accessible cavity of β-cyclodextrin ensures the good adsorption of doxycycline. Furthermore, the Fe₃O₄@SiO₂@mSiO₂-CD nanocomposite can be collected, separated and easily recycled from aqueous solution using an external magnet.

The controllable synthesis of a core–shell structured mesoporous organic–inorganic hybrid nanocomposite, Fe₃O₄@SiO₂@mSiO₂-CD, which demonstrates good adsorption of doxycycline.