Composite Dosage Research Articles

Influential antimony removal from Aquatic Solution using Graphene Nanoplatelet/ Staphylococcus aureus as Novel Composite Adsorbent

Antimony (Sb) is one of the primary pollutants and its compounds and therefore its removal from wastewater and natural waters is significant using effective and eco-friendly adsorbents. Graphene nanoplatelets (GNP) are an important graphene derivative with a varying number of exfoliation cycles which is referred to as multi-layered or few-layered graphene. In this study, Staphylococcus aureus (S. aureus) was immobilized with GNP for adsorption of Sb(III) from the aquatic system. The batch study conditions, composite dosage (100–300 mg/L), Sb(III) initial concentration (1–300 mg/L), pH level (2–8), contact time (10–50 min), and temperature (24–60 °C) were optimized. The adsorption efficiency of the composite was also investigated for wastewater samples including ions K+, Cl−, Na+, Mg2+, Ca2+, NO3−, PO43−, SO42-, and several heavy metal ions. The factorial design is broadly utilized to estimate the statistical correlation among experimental variables and responses. The equilibrium data were studied for Langmuir and Freundlich isotherms under optimized adsorption conditions and the Langmuir adsorption capacity of (qm) of GNP/S. aureus composite was estimated as 116.1 mg g−1. The adsorption kinetic mechanism well followed the pseudo-second order model with a non-linear correlation coefficient (R2 = 0.999). The electrostatic, π–π interactions, and hydrogen bonding interactions as well as surface adsorption make feasible removal of Sb(III) ions onto GNP/S. aureus composite sorbent. The prepared GNP/S. aureus composite is a promising adsorbent to remove Sb(III) ions from aquatic systems.

Preparation and characterization of chitosan-curdlan composite magnetized by zinc ferrite for efficient adsorption of tetracycline antibiotics in water

Tetracycline (TC) antibiotic-related water pollution directly threatens human health and ecosystems. Here, a zinc ferrite/chitosan-curdlan (ZNF/CHT-CRD) magnetic composite was prepared via a co-precipitation method to be used as a novel, green adsorbent for TC removal from water. Benefiting from a multitude of functional groups, CRD was first crosslinked with CHT and then magnetized with ZNF to provide an easy separation from the solution with an external magnetic force. The successful synthesis and magnetization of the composite were verified with different characterization techniques. The effect of solution pH and composite dosage was carefully evaluated. The optimum solution pH and composite dosage were 6 and 0.65 g/L, respectively, with complete TC removal. The adsorption process by the magnetic composite followed the pseudo-first-order kinetics and Langmuir isotherm models. The maximum adsorption capacity determined from the Langmuir model was 371.42 mg/g at 328 K. Thermodynamic parameters indicated endothermic and spontaneous adsorption. Meanwhile, the composite could be readily separated from the aqueous solution thanks to its magnetic property. Then, it was regenerated with acetone and ethanol to be reused for five more successive cycles. Interestingly, the prepared adsorbent was highly stable and performant in removing TC, maintaining approximately 90 % of its first-cycle adsorption capacity. The adsorption mechanism was primarily attributed to electrostatic and hydrogen bonding attractions. Overall, the currently developed adsorbent could be a more favorable, efficient, and cost-effective candidate than other magnetic chitosan-based composites. These features make it applicable for treating water contaminated with various pharmaceutical pollutants with high separation efficiency and easy recovery under successive adsorption-desorption cycles.

Cobalt Ferrite Incorporated Ocimum sanctum Nanocomposite Matrix as an Interface for Adsorption of Organic Dyes: A Sustainable Alternative

AbstractThe preparation of Cobalt ferrite‐Ocimum sanctum nanocomposite, referred to as CoFe2O4/OS, has been reported along with its application for the treatment of water containing hazardous organic contaminants. A simple co‐precipitation approach was applied for synthesis of magnetic nanocomposite, and a thorough analysis for its characterization was conducted using several spectroscopic and microscopic techniques. The characterization results showed that the magnetic nanocomposite exhibited substantial functional groups of Ocimum sanctum powder and magnetic ferrite part. The adsorption investigation of nanocomposite for removal of two cationic dyes was carried out with varying parameters, such as pH, contact time, temperature, concentration, and composite dosage. The sorption process was proved feasible and exothermic at the tested temperatures (303–323 K). The sorption data followed Freundlich and Temkin isotherms which recommended the physisorption progression. The kinetic study revealed a pseudo‐second order rate of sorption process for both dye molecules. The facile preparation, economical cost, significant magnetic character, and high sorption capacity will surely construct the water treatment system more competent with the use of CoFe2O4/OS.

Magnetic Fe3O4/MIL-101 composite as a robust adsorbent for removal of p-arsanilic acid and roxarsenic in the aqueous solution

The p-arsanilic acid (p-ASA) and roxarsenic (ROX) are typical organic arsenic compounds (OACs), which can be evolved into highly poisonous inorganic arsenic species in the aqueous solution. Herein, a magnetic MOFs-based composite of Fe3O4/MIL-101 was successfully obtained by a stepwise solvothermal method and further used in the adsorption of p-ASA and ROX. The structural and physicochemical characteristics of Fe3O4/MIL-101 were firstly investigated in detail. It was found that Fe3O4 microspheres were evenly embedded on the polyhedral MIL-101 surface after the solvothermal process and exhibited a strong superparamagnetic property. After adsorption, a simple external magnetic field can be used to quickly separate the composite from the aqueous solution. The adsorption experiments indicated that the composite is an excellent adsorbent with maximum adsorption capacities of 683.44 and 946.57 mg·g−1 for p-ASA and ROX, respectively. In addition, the effects of composite dosage, initial pH and co-existing anions on the adsorption efficiency were investigated. The main adsorption mechanism consists of the existence of hydrogen bonding, π-π stacking and As-O-Fe coordination between Fe3O4/MIL-101 composite and OACs. We believe that this study would be very meaningful to promote the application of magnetic MOFs based composites for effective adsorption for OACs in the environmental remediation.

The Potential of Spent Coffee Grounds @ MOFs Composite Catalyst in Efficient Activation of PMS to Remove the Tetracycline Hydrochloride from an Aqueous Solution

The efficient removal of Tetracycline Hydrochloride (TC) from wastewater, which is a difficult process, has attracted increasing attention. Aiming to synchronously achieve the goal of natural waste utilization and PMS activation, we have combined the MOFs material with waste coffee grounds (CG). The catalytic activity of the CG@ZIF-67 composite in the TC removal process was thoroughly evaluated, demonstrating that the TC removal rate could reach 96.3% within 30 min at CG@ZIF-67 composite dosage of 100 mg/L, PMS concertation of 1.0 mM, unadjusted pH 6.2, and contact temperate of 293.15 K. The 1O2 and ·SO4- in the CG@ZIF-67/PMS/TC system would play the crucial role in the TC degradation process, with 1O2 acting as the primary ROS. The oxygen-containing functional groups and graphite N on the surface of CG@ZIF-67 composite would play a major role in efficiently activating PMS and correspondingly degrading TC. In addition, the CG@ZIF-67/PMS/TC system could withstand a wide pH range (3-11). The application of CG in preparing MOF-based composites will provide a new method of removing emerging pollutants from an aqueous solution.

Magnetic multi-walled carbon nanotubes as an efficient sorbent for pirimicarb removal from aqueous solutions in continuous (FBAC) and batch formats: thermodynamic, kinetic, isotherm study, optimization and modeling by RSM-ANN

In this study magnetic carbon nanotubes (CNT) were synthesized and used for the removal of pirimicarb insecticide. For characterization of CNT/Fe3O4 nanocomposite, various analyses such as FT-IR, XRD, VSM, SEM, EDX, Map, and TEM were used. The results of this analysis showed that the CNT/Fe3O4 nanocomposite was well-synthesized and had great paramagnetic properties (with Ms = 38.12 emu/g) and effective functional groups. The removal of pirimicarb process by this nanocomposite was performed in fixed bed adsorption column (FBAC) and batch format. In batch format, the effects of pH, contact time, composite dosage, and concentration of pirimicarb were studied using surface response method-central composite design (RSM-CCD) and artificial neural network (ANN). The results of response surface methodology demonstrated that the maximum efficiency of adsorption is 94.62 % while pH, contact time, composite dosage, and concentration of pirimicarb are 6.72, 47.56 min, 1.07 g/L and 43.91 ppm, respectively. Also, RSM-CCD modeling was more capable of expressing the adsorption process than artificial neural network modeling due to higher correlation coefficient and lower error. The equilibrium and kinetic studies showed that the process follows the sips model and pseudo-second-order model respectively and is physically desirable. Also, the mechanism of adsorption was best fitted in double-exponential model and is consisted of both inter and intra-particle diffusion. Thermodynamic studies suggested that pirimicarb adsorption onto CNT/Fe3O4 was a spontaneous and exothermic process. In addition, the results of FBAC showed that the breakthrough time was reduced from 365 min to 9 min by increasing temperature (25 °C, 35 °C and 45 °C) and exhaustion time was diminished by increasing in temperature.

Degradation of Carbamazepine by HF-Free-Synthesized MIL-101(Cr)@Anatase TiO2 Composite under UV-A Irradiation: Degradation Mechanism, Wastewater Matrix Effect, and Degradation Pathway

TiO2 has been hampered by drawbacks such as rapid photoelectron and hole recombination and a wide energy band gap of 3.2 eV. In this study, MIL-101(Cr)@TiO2 was synthesised without any mineraliser (HF) as part of material modification approach to overcome those pitfalls. The composite was well characterized by XRD, FT-IR, TEM, XPS, BET, TGA, and Raman spectroscopy. Under optimal synthesis conditions, the 9.17% MIL-101(Cr)@TiO2 composite exhibited 99.9% CBZ degradation after 60 min under UV-A irradiation. This can be attributed to the delayed recombination of photo-generated h+ and e− and a reduced band gap energy of 2.9 eV. A Type II heterojunction structure was proposed for the composite using the Mulligan function of electronegativity with the calculated Ecb and Evb. Besides, trapping experiments and ESR spectroscopy confirmed O2•− as the main ROS for CBZ degradation. The effects of the operating parameters such as pH, UV intensity, composite dosage, and initial pollutant concentration were also evaluated. The scavenging effects of inorganic and organic constituents of pharmaceutical wastewater on the process were also evaluated, with HCO3−, CO32−, and THF having more significant inhibition on the overall CBZ degradation. The degradation pathways of CBZ were also proposed based on detected intermediates with the aid of LC/MS/MS. The composite illustrated reusability and stability without considerable loss in the degradation performance after repeated runs. This work builds on the development of more effective photocatalysts and provides a glimpse into applications for similar MOF heterojunction photocatalysts.

Corrosion Inhibition of Rumex vesicarius Mediated Chitosan-AgNPs Composite for C1018 CS in CO2-Saturated 3.5% NaCl Medium under Static and Hydrodynamic Conditions

Rumex vesicarius (RVE) mediated chitosan–AgNPs composite was produced in situ by using an aqueous extract of Rumex vesicarius leaves as the reducing agent to reduce Ag+ to Ag0. The synthesized composite was evaluated as a sweet (CO2) corrosion inhibitor (CI) for C1018 carbon steel (CS) in 3.5 wt% NaCl solution under static and hydrodynamic conditions. The corrosion inhibitive performance was evaluated using electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) techniques, as well as scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDAX), and atomic force microscopy (AFM) on corroded C1018 CS without and with additives. The effect of concentration, immersion time, temperature, and rotation speed on the CI performance of the composite was also investigated. The corrosion inhibitive effect increased with increasing composite dosage, with the highest inhibition efficiency (IE) acquired at the maximum composite dosage of 0.3%. Beyond this concentration, the IE decline with increasing concentration. Furthermore, IE was found to increase with immersion time and decline with a temperature rise from 25 to 40 °C, with the optimum temperature of 60 °C found to accelerate corrosion without and with RVE-mediated Chi–AgNPs composite. Under high shear stress, the Chi–AgNPs composite exhibits moderate corrosion inhibition under hydrodynamic conditions. The surface analysis results validate the formation of a protective covering due to composite adsorption on the CS surface. The RVE-mediated chitosan–AgNPs composite could be recommended as a CI for C1018 CS in sweet (CO2) corrosion environments at ambient temperature.

Porous nanocomposites for sorptive elimination of ibuprofen from synthetic wastewater and its molecular docking studies

Pharmaceuticals are a new developing pollutant that is threatening aquatic ecosystems and impacting numerous species in the ecosystem. The aim of this study is the green synthesis of TiO2–Fe2O3-Chitosan nanocomposites in conjunction with Moringa olifera leaves extract and its applicability for ibuprofen removal. Various characterization studies were performed for the synthesized nanocomposites. Box-Behnken design (BBD) is employed to optimize pH, agitation speed, and composite dosage. Equilibrium results show that adsorption process matches with Langmuir isotherm, demonstrating adsorption on the nanocomposite's homogenous surface and follows pseudo-first-order kinetics. Using the BBD, pH, adsorbent dose, and agitation speed were examined as adsorption parameters. Ibuprofen elimination was demonstrated to be most successful at a pH of 7.3, using 0.05 g of nanocomposites at a rotational speed of 200 rpm. Thermodynamic parameters for ibuprofen sorption were carried out and the ΔH and ΔS was found to be 76.23 & 0.233. Molecular Docking was performed to find the interaction between the pollutant and the nanocomposite. UV–vis spectra confirm the 243 nm absorption band corresponding to the nanocomposite's surface plasmon resonances. Fourier transform infrared spectroscopy spectra relate this band to a group of nanocomposites. The findings of this work emphasize the importance of TiO2–Fe2O3-Chitosan nanocomposites for removing ibuprofen from wastewater.

Synthesis and characterization of novel polymeric-sepiolite composite resin for effective water softening: applications in batch and column adsorption

ABSTRACT A novel polymeric composite resin, based on sepiolite and polyacrylonitrile (Sep/PAN), was synthesised and characterized using Fourier transform infrared spectrometry (FTIR), X-ray diffraction spectrometry (XRD), thermogravimetric analysis (TGA), and scanning electron microscope-energy dispersive X-ray (SEM-EDX). The thermal, morphological, and surface properties of the composite were improved by the presence of Sep. Furthermore, the prepared composite was applied for the removal of water hardness using both batch and column techniques. The effects of parameters, such as Sep content ratio, contact time, composite dosage, and hardness concentration, were studied. The Sep/PAN composite increased the removal efficiency of water hardness by 26% when compared to the pure Sep. For synthetic water samples, the Sep/PAN showed 100% removal efficiency within 60 min, with an optimum composite resin dosage of 3 g per 1 L of hard water and a corresponding experimental adsorption capacity of 316 mg/g. The adsorption results were observed to fit a pseudo-second-order kinetic model and a Freundlich adsorption isotherm model. Correspondingly, the column breakthrough capacity of the prepared composite resin was studied under various operating conditions. The composite performance for hardness removal from natural water samples, with a total hardness of 237-680 mg CaCO3/L, was assessed. The results demonstrated an efficiency range of 81-100%. These results suggested potential applications of the Sep/PAN composite for water softening, circumventing some of the difficulties in using clay alone while providing higher levels of efficiency.

One-pot synthesis of metal oxide-clay composite for the evaluation of dye removal studies: Taguchi optimization of parameters and environmental toxicity studies.

The present study demonstrates the synthesis of eco-friendly metal oxide-clay composites (MgO-clay and CaO-clay) with phytochemical functionalization. The physical and chemical properties of prepared composites were characterized using standard techniques viz. scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The effect of pH on the dye adsorption capability of the synthesized composites was studied. The adsorption of an anionic dye methyl orange (MO) and a cationic due methylene blue (MB) was favored in the acidic and basic regions, respectively. The Taguchi design approach was adopted for the removal of MO and MB from wastewater using the synthesized composites. The obtained results suggest that initial dye concentration and composite dosage were the most influential parameters in dye removal among all the studied parameters. The adsorption experiments were carried out using MgO-clay and CaO-clay composites with the optimum conditions obtained from Taguchi optimization to validate the predicted response. The experimental parameters viz. the effect of contact time, initial dye concentration, and solution temperature were studied for screened composite (CaO-clay) with optimized conditions. The obtained results were interpreted using standard isotherms and kinetic models. A maximum adsorption capacity of 571 ± 10 and 859 ± 14mgg-1 was obtained from the Langmuir adsorption isotherm for MO and MB, respectively. Regeneration studies suggested that the CaO-clay composite can be utilized up to 3 cycles with reduced adsorption capacity of the dyes over cycles due to the solid binding nature of dyes on the CaO-clay composite. The fresh and utilized CaO-clay composite were tested for their environmental toxicity analysis using ecologically important soil microorganisms. The obtained results suggested no detrimental effects on soil microbe's functionality, indicating their threat-free disposal in the soil environment.

Adsorption of Cu2+ and Pb2+ from Municipal Wastewater by Intercalation Polymerization Modified Kaolin

Adsorption method has attracted extensive attention in heavy metal wastewater treatment due to its low cost, abundant sources, and simple operation. Kaolin is utilized as raw material, waterborne polyurethane is utilized as dispersion medium, and dimethyl sulfoxide (DMSO) is utilized as intercalation agent, to prepare intercalation polymerization modified kaolin material (KBEP). It is then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry (TG), and other methods. The polymer is utilized for static adsorption of Cu2+ and Pb2+, and the kinetic analysis of the adsorption process is carried out. The results show that the layer spacing of kaolin increases substantially (from 0.69 nm to 0.81 nm) after modification. When the content of kaolin is less than 1.7%, kaolin exists in intercalation or stripping state in waterborne polyurethane matrix. When the content of kaolin is higher than 1.7%, kaolin can exist in the form of agglomeration with waterborne polyurethane matrix. Compared with pure polyurethane, the composite’s thermal stability is improved, and the maximum thermal weight loss of the hard section is increased by 50 °C. When kaolin content is 2.5%, the temperature of the hardness and the fastest thermal decomposition rate of the soft section increases by 30 °C and 26 °C, respectively. The adsorption test reveals that the Cu2+ elimination rate reaches 93.7% when the addition amount of the prepared material reaches 1.5 g/L. When the addition amount of the prepared material reaches 0.6 g/L, the Pb2+ elimination rate reaches 95.8%. With the increase of the dosage of kaolin composite, the adsorbability of the polymer to the two metal ions decreases gradually. Kinetic experiments show that the adsorption of Cu2+ and Pb2+ is in line with the pseudo-second-order kinetic (PSOK) equation. The adsorbability of Cu2+ and Pb2+ is 75.3 mg/g and 268.6 mg/g, respectively. The adsorption way is mainly chemical adsorption.

Removal of Diclofenac-Na from aqueous solution onto H3PO4 modified composite clay

Under batch experiment conditions, this work seeks to successfully remove Diclofenac-Na (DCF-Na) from an aqueous solution utilizing a composite sorbent made of Bentonite, Kaolinite clay, and Worm casting (BKW). This study investigated the structural modification of the H3PO4 Modified Clay by X-ray fluorescence and the effect of selected adsorption factors – DCF-Na concentration and modified BKW composite dosage. The concentration equilibrium data was used to study six isotherm models. Freundlich isotherm model better explained the adsorption of DCF-Na onto modified BKW composite with a correlation coefficient close to 1. Kinetics models were examined, and the Elovich model gave a better fit than other kinetic models studied. Mass diffusion mechanisms and thermodynamics studies were successfully carried out. The enthalpy change values evaluated were negative, which revealed the spontaneity of DCF-Na remediation onto modified BKW, and that DCF-Na adsorption is exothermic and occurred through a physisorption process.

Carboxyl functional poly(ionic liquid)s confined in metal–organic frameworks with enhanced adsorption of metal ions from water

Development of porous adsorption materials tethered with functional groups was favorable to establish a more efficient, stable and broad-spectrum metal ions removal strategy from water. In this work, carboxyl functional poly(ionic liquid)s@MOF composites were prepared through in situ polymerization of ILs monomers inside MOF pores. Their thermophysical property, structure and morphology were characterized by different techniques. These PILs@MOF composites were proposed as universal and efficient adsorbents to remove selected rare earth metal ions (La3+, Sm3+, Nd3+) and heavy metal ions (Pb2+, Cd2+) from water medium. Effect of pH value and composite dosage on the adsorption efficiency were studied in detail. The optimized adsorption efficiency as high as 99.8 % could be found for the selected metal ions by PIL@MIL-101. In addition, the isotherms, kinetics and thermodynamic parametersof the adsorption process were also determined, and these results imply that the Langmuir model and pseudo-second-order model fitted well with the experimental data. Thermodynamic parameters revealed spontaneous and exothermic nature of the adsorption process. A plausible mechanism for the adsorption process was suggested by the electrostatic interaction and coordination between the carboxyl group and metal ions with the aid of FTIR and XPS measurements. Finally, recycling experiments were performed to demonstrate the recyclability and stability of PIL@MOF composites undergoes at least five adsorption–desorption runs. The current research presented a series of poly(ionic liquid)s@MOF composites as a universal adsorption platform that demonstrated great potential for removing metal ions with remarkable efficiency.

Design of xerogel pill with good swallowing performance through wet milling and drop freeze-drying processes

A novel dosage form with dose-adjusting and swallow-assisting functions, named “xerogel pills,” was developed for pediatric or geriatric patients. It is a multiple-unit dosage form in which a single dose is divided into several pills. The pills are double-structured small spheres with an inner drug core and an outer dried-gel layer (xerogel shell). In this research, the preparing method (formulation and process) of the xerogel pills was established by using a combination of wet-milling and drop freeze-drying (DFD) techniques. Fexofenadine hydrochloride (FXF) was used as a poorly water-soluble model drug. Xanthan gum (XG), a gelling agent, was formulated to attain a smooth and soft mouth-feeling. The internal fluid consisting of the FXF nanosuspension prepared through the wet-milling process and the external fluid consisting of an XG solution were separately fed to a two-fluids nozzle composed of central and peripheral nozzles. Both fluids were concentrically dropped together into liquid nitrogen to construct double-structured droplets. After the freeze-drying process, the xerogel pills were formed. Mannitol (MNT), as a filler, was co-formulated with both fluids to strengthen the pills physically. The resultant pills were around 5–6 mm in diameter with a spherical shape, uniform size, and low density, enabling them to be easily swallowed, and quickly gelled upon contact with water. The FXF amount in one pill was 7–9 mg, depending on the XG loading in the external fluid. The relative standard deviation (RSD) of the FXF amount were varied in the range of around 3–10%, suggesting that the content uniformity would be acceptable as a composite dosage unit containing five or more pills. It was assumed that further improvements of the physical strength and drug content uniformity would be required to introduce the xerogel pills to practical use.

Sono-synthesis of cellulose-TiO2 nanocomposite adsorbent for fast cleaning of anionic dyes containing wastewater

This work was devoted to synthesizing a composite of cellulose-TiO2 by the in-situ process using the sol-gel method and applied on representatives of acid dyes to determine the functionality regarding the adsorption of dyes from aqueous solution. The composite particle adsorbed 100% dyes within 3 min of the direct application. XRD, FTIR, SEM, and Zeta potential tests were conducted to investigate the effect of crystal, molecular structure, surface morphology, and surface charges on the absorption speed of cellulose-TiO2 composite particles. The experimental results revealed that the cellulose was partially hydrolyzed by concentrated hydrochloric acid and left some positive charge on the surface of cellulose during the synthesis of the composite structure. The test results demonstrated that nano TiO2 with a thin layer of cellulose covered the surface of undegraded cellulose particles. The structural changes in the composite made them beneficial to fast dye adsorption. The effect of initial dye concentration, composite dosage, and temperatures were also investigated to find the optimum condition for dye adsorption. The optimum condition was found at the initial concentration of 400 mg/l, dosage of 0.10 g, and temperature of 25 °C. The removal efficiency and maximum adsorption capacity at this condition were 100% and 40 mg/g, respectively. The adsorption data suggested that the data was well fitted with a pseudo-second-order model for adsorption kinetics and Langmuir model for adsorption isotherm. Thermodynamic analysis revealed that the adsorption process was physisorption, spontaneous, random, and endothermic. Overall, in this work, the developed cellulose-TiO2 nanocomposite might be an economical and efficient adsorbent to remove dyes from wastewater.

Chromium(VI) removal from synthetic solution using novel zero-valent iron biochar composites derived from iron-rich sludge via one-pot synthesis

In this study, Fe-rich sludge obtained from coagulation–flocculation of swine wastewater was processed into zero-valent iron (ZVI) biochar composites through one-pot pyrolysis at 700 °C under anoxic (MBCN700) and hypoxic (MBCA700) conditions. X-ray diffraction analysis revealed that α-Fe0 and γ-Fe0 were the dominant Fe species in MBCN700 and MBCA700, respectively. The effects of different process parameters, including composite dosage, initial Cr(VI) concentration, pH, dissolved O2 (DO), and contact time on Cr(VI) removal from synthetic solutions were evaluated. The results showed that both the acidic initial pH and DO contributed to Cr(VI) removal; the highest removal rate was observed at pH 3. Based on the Langmuir isotherm model, the predicted maximum removal capacity of MBCA700 was greater than that of MBCN700, primarily because of its core-shell structure, less corrosive ZVI, and higher degree of graphitization. X-ray photoelectron spectroscopy analysis coupled with fitting of the kinetic (pseudo-second-order) and isothermal (Freundlich) data suggested that Cr(VI) removal by MBCN700 occurred via adsorption, FeC micro-electrolysis, and co-precipitation. In contrast, the removal mechanism for MBCA700 included adsorption, reduction, and electrostatic attraction. Thus, ZVI biochar composites can serve as potential remediators of Cr(VI)-contaminated wastewater.

Enhanced removal of glyphosate from aqueous solution by nano-CaO2/AS composite: Oxidation and precipitation

The massive use and accumulation of glyphosate will cause a series of ecological and environmental problems, so there is an urgent need for effective treatment and recovery methods of glyphosate. In this research, based on the properties of CaO2 that can provide both reactive oxygen and Ca2+, nano-CaO2 was selected as the oxidant and precipitant. Meanwhile, an iron-containing alkaline soil (AS) was used as a dispersant for nano-CaO2 as well as a catalyst to reinforce the advanced oxidation. The nano-CaO2/AS composite with high reactivity was successfully prepared by a simple precipitation method. Due to the activation of OH• by the iron-containing substances, the addition of AS greatly enhanced the removal efficiency of glyphosate in the advanced oxidation system. The influences of composite dosage, initial pH value, coexisting substances, and initial glyphosate concentration on the degradation of glyphosate were investigated. The results indicated that acidic conditions were favorable for the advanced reaction process, and common coexisting substances had rarely adverse impacts on the removal of glyphosate. In addition, possible degradation mechanism of glyphosate was proposed based on the free radical quenching experiments and characterization analyses. The removal of glyphosate by nano-CaO2/AS composite was a synergistic action of advanced oxidation and precipitation, and OH• and O- 2• were the main active radicals involved in the reaction system. Most of glyphosate can be oxidized to inorganic anions. The HPO2- 4decomposed by glyphosate combined with Ca2+ dissolved from nano-CaO2 in solution to produce the precipitation of CaHPO4·2H2O. The solid precipitation was rich in available phosphorus and can be recycled as a phosphorus fertilizer, which could promote the plant growth. Therefore, the nano-CaO2/AS composite is a promising material for glyphosate wastewater treatment and phosphorus recovery.

Nano zero-valent iron loaded corn-straw biochar for efficient removal of hexavalent chromium: remediation performance and interfacial chemical behaviour.

To improve the poor stability of nano zero-valent iron (nZVI), corn-straw biochar (BC) was used as a support for the synthesis of composites of nZVI-biochar (nZVI/BC) in different mass ratios. After a thorough characterization, the obtained nZVI/BC composite was used to remove hexavalent chromium [Cr(vi)] in an aquatic system under varying conditions including composite amount, Cr(vi) concentration, and pH. The obtained results show that the treatment efficiency varied in the following order: nZVI-BC (1 : 3) > nZVI-BC (1 : 5) > nZVI alone > BC alone. This order indicates the higher efficiency of composite material and the positive effect of nZVI content in the composite. Similarly, the composite dosage and Cr(vi) concentration had significant effects on the removal performance and 2 g L-1 and 6 g L-1 were considered to be the optimum dose at a Cr(vi) concentration of 20 mg L-1 and 100 mg L-1, respectively. The removal efficiency was maximum (100%) at pH 2 whereas solution pH increased significantly after the reaction (from 2 to 4.13). The removal kinetics of Cr(vi) was described by a pseudo-second-order model which indicated that the removal process was mainly controlled by the rate of chemical adsorption. The thermodynamics was more in line with the Freundlich model which indicated that the removal was multi-molecular layer adsorption. TEM-EDS, XRD, and XPS were applied to characterize the crystal lattice and structural changes of the material to specify the interfacial chemical behaviour on the agent surface. These techniques demonstrate that the underlying mechanisms of Cr(vi) removal include adsorption, chemical reduction-oxidation reaction, and co-precipitation on the surface of the nZVI-BC composite. The results indicated that the corn-straw BC as a carrier material highly improved Cr(vi) removal performance of nZVI and offered better utilization of the corn straw.

Spontaneous nutrient recovery and disinfection of aquaculture wastewater via Mg–coconut shell carbon composites

Aquaculture wastewater contained large amounts of pathogenic microorganisms, nitrogen (N) and phosphorus (P). In this study, the nutrient recoveries and wastewater disinfection were simultaneously achieved using Mg–coconut shell carbon (Mg–CSC). The composites were prepared by a ball milling method. The hydrogen peroxide (H2O2) was in-situ generated by the dissolved oxygen reduction driven by Mg corrosion on the CSC surface, which inactivated the microorganisms. Besides that, Mg corrosion provided sufficient Mg ions and appropriate pH conditions for struvite formation. The results show that 5.4-log E.coli removal was achieved under different conditions. Improving the Mg/CSC ratio and composite dosage could shorten the time required for disinfection. In addition to H2O2, singlet oxygen played a critical role. Reactive oxygen species destroyed the cellular structure and killed the bacteria. The recoveries of NH4+-Nand P under certain conditions were about 60% and 91%, respectively. An increased composite dosage could improve the recovery ratio of P. Excessive dosages were not beneficial for removing NH4+-N. The characterization result revealed that struvite crystals were the main precipitates on the CSC surface. The Mg–CSC composites also revealed satisfied nutrient recovery and disinfection performances in the real aquaculture wastewater treatment process.