Adsorption Capacity For Sulfamethoxazole Research Articles

Unary adsorption of sulfonamide antibiotics onto pozzolan-tyre ash based geopolymers: Isotherms, kinetics and mechanisms

In this contribution, geopolymer composites, GP0, GP5-TA and GP10-TA, were prepared by alkaline activation and substituting pozzolan (Pz) with 0, 5 and 10 wt% of tyre ash (TA), respectively. The geopolymers were characterized using standard methods (XRD, TGA, FTIR, BET, SEM, Boehm titration and methylene blue and iodine indices) and were applied for the abatement of two sulfonamides, sulfamethoxazole (SMX) and sulfadimethoxine (SDM) in single-solute solutions. The effects of pH, salinity, initial concentration and contact time were evaluated. The incorporation of 5 and 10% TA increased the specific surface area (SSA) of pristine geopolymer (GP0) from 13.62 to 21.48 and 29.70 m2.g−1, respectively. The equilibrium data was best described by the Sips isotherm model. Salinity significantly diminished the adsorption of SMX and SDM. In aqueous medium, the geopolymers exhibited higher adsorption capacity for SDM (log Kow, 1.17) relative to SMX (log Kow, 0.86). In contrast, in saline medium, SMX uptake was higher, suggesting a cation-mediated adsorption. Adsorption of SMX was uncharacteristically independent of pH, whereas SDM uptake was significantly pH-dependent. The GP5-TA geopolymer composite exhibited the highest adsorption capacity for SMX in a saline environment (46.69 mg.g−1) and for SDM in non-saline water (107.69 mg.g−1). Adsorption rate was described by the pseudo-second order kinetic law. Adsorption mechanism was multi-mechanistic involving hydrophobic, ion exchange and charge assisted hydrogen bonding and electrostatic interactions in the case of SDM. Future works should optimize the functional groups density of active sites especially for sulfonamides in saline waters.

Characteristics and mechanisms of sulfamethoxazole adsorption onto modified biochars with hierarchical pore structures: Batch, predictions using artificial neural network and fixed bed column studies

A series of modified biochar with hierarchical pore structures (ZnxBC1, x = 0.5, 1, 2, 3) was obtained by ZnCl2 and investigated the adsorption performance of sulfamethoxazole (SMX). The structure and composition of ZnxBC1 were well characterized by the material analysis technique. Compared with unmodified biochar (BC), the specific surface area, pore volume, and adsorption capacity of ZnxBC1 significantly increased. The ZnxBC1 performed a significant adsorption capacity of SMX with the maximum adsorption amount of 597.57 mg/g, leading to a 54-fold increase in that of BC (11.04 mg/g). Multiple linear regression analysis showed that the quantitative relationship of qe with Vmeso and Vmicro was qe = 360.74*Vmeso + 871.58*Vmicro-22.26, which was the novelty of the study to the analysis of SMX adsorption capacity on the different Vmeso/Vmicro ratios of adsorbents. Based on the batch experiment results, an artificial neural network (ANN) model with a topology of 5:5:10:1 was developed to sufficiently describe the adsorption data (R2 > 0.99), and possessed good predictability in different water quality conditions. Additionally, both static adsorption and dynamic adsorption experiments of Zn1BC1 showed excellent regeneration properties. Overall, the ZnCl2 modified biochar with the properties of rapid adsorption rate, high adsorption capacity, multiple reuses, and low-cost performed the potential utilization for the removal of SMX, and the effect of pore structure of biochar on SMX adsorption could guide the design and preparation of efficient antibiotics adsorbents.

Influence of adsorption sites of biochar on its adsorption performance for sulfamethoxazole

In this study, the effects of various types of key adsorption sites on biochar were investigated on its adsorption capacity for sulfamethoxazole (SMX). The biochar obtained by carbonization of corncob at 800 °C (named CC800) was applied to the adsorption of SMX in aqueous environment. The adsorption of SMX by CC800 exhibited a “Three-stage downward adsorption ladder” characteristic in the whole pH range, which was attributed to the different mechanisms corresponding to different adsorption sites of CC800. The organic solvent method and heat treatment method restored the adsorption sites of CC800 after saturated adsorption. And the results revealed that the pore structure and aromatic structure under acidic conditions, and surface functional groups and pore structure under alkaline conditions were confirmed to be key SMX adsorption sites. The adsorption energies of each adsorption mechanism were calculated by density functional theory (DFT), and their order was (−)CAHB (–COO–) > π+−π EDA interaction > (−)CAHB (–O–) > pore filling mechanism > π−π EDA interaction. Based on the above studies, the adsorption performance of biochar to SMX can be improved by targeted modification of its micropore structure, surface functional groups, and aromatic structures.

Molecular imprinting functionalization of magnetic biochar to adsorb sulfamethoxazole: Mechanism, regeneration and targeted adsorption

Sulfamethoxazole (SMX), a typical medical antibiotic, is regarded as a major risk in the surface hydrosphere because of its harmful biological reaction and potential to trigger bacterial resistance. Ameliorating the hydrosphere will become more convenient if the challenging adsorption and separation of SMX in hydrosphere are achieved. To reveal the mechanism, regeneration and targeted adsorption of SMX on a novel surface-imprinted polymer (MIP-MBC) and batch experiments were carried out in this study. MIP-MBC was prepared in organic solution using a Fe-Mn-modified biochar to selectively adsorb SMX in a water solution. Owing to the mesopores and oxygen-containing functional groups of MIP-MBC, imprinted cavities in pores are found to lead to a remarkable adsorption efficiency for SMX. The maximum adsorption capacity for SMX reaches up to 25.65 mg g−1, which is 1.34 times that of the non-molecularly imprinted magnetic biochar (NIP-MBC). The adsorption process matches well with the second-order kinetics and Freundlich thermodynamic model, which indicates that hydrogen bonds and electrostatic interactions are simultaneously involved in the adsorption process. After five cycles, the adsorption rate for MIP-MBC reaches 88.34%. Furthermore, MIP-MBC is applied to the binary system to remove SMX, and it can be used to accurately identify and adsorb SMX due to K`> 1 and being independent of the ion concentration. The high affinity site plays a major role in the imprinting process for SMX. This study furnishes a novel perspective for promoting the practical application and economic benefits of targeted biochar material to capture SMX in sewage purification.

Evaluation of a ZnCl2-modified biochar derived from activated sludge biomass for adsorption of sulfamethoxazole

Sulfamethoxazole (SMX) was effectively removed from aqueous solution via adsorption to a chemically modified biochar created using a simple and rapid microwave (MW) pyrolysis of activated municipal wastewater sludge. Response surface methodology (RSM) was used to maximize SMX adsorption capacity optimizing three independent synthesis parameters including ZnCl2 concentration (0.5–1.5 mol/L), MW time (3–10 min), and MW power (400–1000 W). ZnCl2 modified biochar (ZnBC) synthesized under the optimized conditions (ZnCl2 concentration = 1.5 mol/L, MW time = 8 min, and MW power = 915 W) was analyzed by different characterization techniques including Brunauer Emmett and Teller (BET) surface area analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), and point of zero charge (pHpzc). ZnCl2 impregnation coupled with a homogenous MW heating profile led to improved accessibility of surface functional groups with a specific surface area of 214 m2/g and robust porous structure with an average pore volume of 0.127 cm3/g. Adsorption experiments using the optimized ZnBC resulted in a 89% SMX removal efficiency and maximum SMX adsorption capacity of 50.6 mg/g. Isotherm and kinetic analysis suggested multilayer chemical adsorption of SMX over a heterogeneous biochar surface followed by heterogenous pore diffusion into the ZnBC pores. Results showed that acidic pH favors SMX removal through a spontaneous and exothermic process. The application of modified activated sludge-based biochar introduces a new sustainable method for treating pharmaceuticals and recycling waste sludges from wastewater treatment plants.

Efficient Adsorption of a Sulfonamide Antibiotic in Aqueous Solutions with N-doped Magnetic Biochar: Performance, Mechanism, and Reusability.

Conventional biochar has limited effectiveness in the adsorption of sulfonamide antibiotics, while modified biochar exhibits greater adsorption potential. Residues of sulfamethoxazole (SMX) in the aquatic environment can threaten the safety of microbial populations as well as humans. In this study, iron-nitrogen co-doped modified biochar (Fe-N-BC) was prepared from palm fibers and doped with Fe and urea via synthesis at 500 °C. Fe-N-BC has a richer surface functional group based on elemental content, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller (BET) specific surface area test exhibited Fe-N-BC, which possessed a greater surface area (318.203 m2/g) and a better developed pore structure (0.149 cm3/g). The results of the hysteresis loop and the Raman spectrum show that Fe-N-BC has a higher degree of magnetization and graphitization. Fe-N-BC showed a remarkable adsorption capacity for SMX (42.9 mg/g), which could maintain 93.4% adsorption effect after four cycles, and 82.8% adsorption capacity in simulated piggery wastewater. The adsorption mechanism involves pore filling, surface complexation, electrostatic interactions, hydrogen bonding, and π-π EDA interactions. The results of this study show that Fe-N-BC prepared from palm fibers can be a stable, excellent adsorbent for SMX removal from wastewater and has promise in terms of practical applications.

Do microplastics affect sulfamethoxazole sorption in soil? Experiments on polymers, ionic strength and fulvic acid

Microplastics (MPs) and sulfamethoxazole (SMX) are emerging contaminants that are ubiquitous in the soil environment. In this study, we investigated MPs polymer type and soil environmental factor effects on SMX adsorption behavior in the soil system. Our results showed that MPs dosage affected the soil particles' SMX adsorption rate and capacity (Qe). Adding 1 % polystyrene (PS) increased the SMX adsorption rate significantly. The value of K1, which represented the adsorption rate, increased from 0.569 h−1 to 1.019 h−1. However, the addition of MPs reduced the soil's SMX equilibrium adsorption capacity slightly. Moreover, increasing salinity strength enhanced SMX adsorption capacity by MPs significantly. However, increasing calcium ions concentration decreased SMX adsorption in the MPs amended soil due to multivalent cationic bridging and competitive adsorption mechanisms. In addition, we observed that fulvic acid addition inhibited SMX adsorption. This study suggests that the addition of MPs reduced the adsorption of SMX in the soil slightly due to dilution effect. Meanwhile, changes in environmental factors also affected the adsorption behavior of SMX in soil amended with MPs.

Converting Hybrid Mechanisms to Electron Transfer Mechanism by Increasing Biochar Pyrolysis Temperature for the Degradation of Sulfamethoxazole in a Sludge Biochar/Periodate System

In this study, sludge biochar was prepared under four pyrolysis temperatures (SBC300, SBC500, SBC700, and SBC900) and then was employed to activate periodate (PI) for the degradation of sulfamethoxazole (SMX). Various characterization methods were employed to investigate the effect of pyrolysis temperature on the physicochemical properties of sludge biochar and the activation capacity of periodate. The SMX adsorption capacity of SBCs and the ability of activating PI to degrade SMX increased with the increasing pyrolysis temperature. The degradation of SMX by the SBCs/PI systems was highly dependent on the initial pH of the solution and the dosage of SBCs. Mechanistic studies indicated that the degradation of SMX by the SBCs/PI system was mainly based on an electron-mediated transfer mechanism. Additionally, the electron transfer capacity of the SBCs affected the defects and the degree of graphitization. The contribution of free radicals to SMX degradation decreases with increasing pyrolysis temperature. Toxicity experiments demonstrated that the toxic elimination of SMX by the SBCs/PI system was enhanced with increasing pyrolysis temperature.

Evaluation of the adsorption of sulfamethoxazole (SMX) within aqueous influents onto customized ordered mesoporous carbon (OMC) adsorbents: Performance and elucidation of key adsorption mechanisms

Antibiotic resistance genes represent treatment challenges for wastewater treatment systems. These resistance genes are a direct outcome of insufficient treatment of antimicrobial substances within wastewater treatment plants. Thus, this research work concentrated on a typical antibiotic sulfamethoxazole (4-amino-N-[5-methyl-3-isoxazolyl]-benzene sulfonamide or SMX). In this study, the effectiveness of SMX adsorption onto ordered mesoporous carbon (OMC) was first systematically evaluated. SEM, TEM, and BET were used to examine the morphology of OMCs, while XPS, FTIR, and Boehm titration were used to determine the functional groups present on OMCs. The specific surface was found to be 1395.31 m2/g for OMC-900. The behavior of adsorbing SMX onto OMCs was evaluated using kinetics and isotherms studies. The influence of solution pH, temperature, coexisting ions, and natural organic matter (NOM) were also evaluated as to their impacts on SMX adsorption. The results revealed that the mesopores in OMC contributed significantly to SMX adsorption capacity. Adsorption achieved equilibrium after 4 h with an adsorption capacity of 334 mg/g. The Pseudo Second Order Kinetic Model provided a good fit for the adsorption kinetic processes of SMX. The Freundlich Isotherm Model, which suggests physical adsorption, provides a better fit for adsorption isotherm data. The adsorption of SMX onto OMC was exothermic and spontaneous, according to thermodynamic analyses. Most importantly, the adsorption mechanisms of SMX onto OMC include hydrogen bonding and electrostatic interaction. Additionally, a key adsorption mechanism was found to be the affinity (π- π interactions) between the aromatic structures of OMC and the benzene ring in SMX molecule. This study reports a thorough understanding of adsorption components and mechanisms involved in the adsorption of SMX onto OMCs and also the regeneration of OMCs after adsorption.

FeCl3-activated biochar catalyst for heterogeneous Fenton oxidation of antibiotic sulfamethoxazole in water

One-step FeCl3-mediated pyrolysis/activation was developed for preparation of bermudagrass (BG)-derived FeCl3-activated biochars (FA-BCs) from bermudagrass (BG) as a heterogenous Fenton catalyst for heterogeneous Fenton oxidation of sulfamethoxazole (SMX) in water. The FA-BC prepared at the FeCl3 to BG mass ratio of 2 (FA-BC) exhibited higher adsorption and Fenton oxidation of SMX than other mass ratios of the FeCl3 to BG. FA-BC presented the great surface area (835 m2/g) and high SMX adsorption capacity (195 mg SMX/g BC), which was higher than various BCs in the previous studies. Additionally, the surface of FA-BC was attached with Fe2O3, Fe0, and Fe3O4 after the FeCl3 activation. Under the optimal conditions for Fenton reaction (SMX concentration, 100 mg/L; loading of FA-BC, 0.1 g/L; dose of H2O2, 200 mg/L; temperature, 20 °C; pH 3; reaction time, 12 h), SMX and COD removal efficiencies reached 99.94% and 65.19%, respectively. Increasing reaction temperature from 20 to 50 °C significantly improved the SMX oxidation rate from 0.46 to 1.04 h−1. The HO· radicals were proved to play a major role during the Fenton oxidation of SMX. In addition, the SMX solution treated by Fenton oxidation showed much less toxicity than the initial SMX solution. Additionally, the reusability tests of FA-BC indicated that 89.58% removal efficiency for SMX was still achieved after 3 cycles of Fenton oxidation under the optimal conditions. Furthermore, FA-BC can also efficiently remove SMX from the dairy wastewater. Therefore, FA-BC showed a high potential to eliminate aqueous SMX through adsorption and heterogeneous Fenton oxidation.

Insight into the activation mechanisms of biochar by boric acid and its application for the removal of sulfamethoxazole

Sulfamethoxazole (SMX) is frequently detected in the environment and causes a huge threaten to human health. Biochar (BC) is a metal-free adsorbent and generally exhibits a good adsorption capacity for SMX. However, the current activated methods usually result in the high energy consumption and low yield of the biochar. In this study, biochar was activated by boric acid under limited oxygen condition. The yield of biochar was increased by 103% after the activated by boric acid. The specific surface area of BC was significantly increased from 766.6 m2·g−1 to 1190.6 m2·g−1. The intensity of the (111) diamond peak of B-BC was higher than that of BC, suggesting that boric acid affected the surface pyrolysis temperature of biochar. The proposed roles of boric acid in the activation process were to: 1) enhance the generation of micropores during the pyrolysis process; 2) improve the yield of biochar via the transformation pathways of C-corresponding bonds and physical blocking. The boric acid activated biochar (B-BC) had a higher adsorption capacity for SMX than BC under the various aqueous conditions. Hence, boric acid activated biochar is a promising porous adsorbent to enhance the removal of SMX and achieve practical application.

Adsorption removal of sulfamethoxazole from water using UiO-66 and UiO-66-BC composites

The adsorption removal of anti-inflammatory drugs from water by diverse materials has drawn great attention. This study investigated the adsorption of sulfamethoxazole (SMX) by two types of materials, UiO-66 and UiO-66-BC composites. Highly porous MOF composites with functional groups were synthesized by combining UiO-66 with corncob-based biochar at different molar ratios. SEM results showed that macroporosity of UiO-66-BC composites was increased by increasing the ratio of biochar. It was found that UiO-66-BC composites displayed highly improved adsorption performance of SMX relative to pristine UiO-66. UiO-66-BC (5%) had the highest SMX adsorption capacity, about 2.4 times those of pristine UiO-66. It was the high surface area of UiO-66 and redundant functional groups of biochar that increased the adsorption performance of composites. Moreover, UiO-66-BC can be reused and displayed the competitive adsorption efficiency after successive adsorption, which made it a potential adsorbent for the removal of SMX from water.

Sorption of Sulfamethoxazole on Inorganic Acid Solution-Etched Biochar Derived from Alfalfa.

The properties of alfalfa-derived biochars etched with phosphoric (PBC) or hydrochloric acid (ClBC) compared with raw materials (BC) were examine in this paper. SEM, FT-IR, XRD, BET and elemental analysis were performed to characterize the micromorphology and chemical structure comprehensibly. The results showed that the porous structure was enhanced, and surface area was increased via etching with inorganic acids. Batch adsorption experiments were performed for sulfamethoxazole (SMX) to biochars. The experimental data showed that modified biochars exhibited higher adsorption capacity for SMX, i.e., the adsorption quantity of ClBC and PBC had risen by 38% and 46%. The impact on pH values suggested that the physisorption, including pore-filling and electrostatic interaction, might be applied to original biochar. In addition, chemisorption also played a role, including hydrogen bonding, π-π electron donor acceptor interaction (π-π EDA), and so on. Furthermore, both pH and coexisting ions also had a certain effect on sorption. Enhancement of the electrostatic attraction between biochar and SMX might also account for the enhanced capacity of SMX at pH < 7, and coexisting ions could decrease the amount of SMX adsorbed onto biochars, mainly because of competition for adsorption sites.

Enhanced adsorption of sulfonamides by a novel carboxymethyl cellulose and chitosan-based composite with sulfonated graphene oxide

A novel multiple active sites sponge was fabricated from carboxymethyl cellulose (CMC) and genipin crosslinked carboxyalkyl-chitosan (GCC) combined with sulfonated graphene oxide (CMC/SGO–GCC) and used as a material for adsorbing sulfonamide antibiotics. The GO contains a variety of carboxyl and hydroxyl groups, which can interact with the hydroxyl groups of chitosan and CMC to form strong hydrogen bonds. This adsorption process is spontaneous and pH dependent, and shows high sulfamethoxazole (SMX) and sulfapyridine (SPD). Removal efficiency from aqueous solutions. Equilibrium adsorption studies showed that the maximum adsorption capacities of SMX and SPD decreased from 312.28 to 272.83 mg/g and 161.89 to 146.56 mg/g, respectively, as the temperature increased from 298 to 318 K. Reusability experiments indicated that CMC/SGO–GCC maintained a high adsorption capacity for SMX and SPD upon its reuse. This study shows that CMC/SGO-GCC is an ideal material for adsorbing SMX and SPD.

Aqueous adsorption of sulfamethoxazole on an N-doped zeolite beta-templated carbon

A zeolite beta-templated carbon (BTC) and its N-doped form (nBTC) were prepared and used for the adsorptive removal of sulfamethoxazole (SMX) antibiotic from water. Both demonstrated excellent adsorption properties, and the maximum adsorption capacity of nBTC (1367 mg/g) was exceptionally high, and surpassed those of other adsorbents reported to date. Adsorption kinetic studies indicated that the adsorption was efficient, and adsorption equilibrium was reached within 10 min. The excellent adsorption performance of nBTC was attributed to the high-surface-area hydrophobic carbons with strong π–π interactions and H-bonding in the uniform microporous geometry of the material. The effect of the solution pH and thermodynamics of the adsorption process were subsequently investigated. nBTC was easily regenerated by washing with acetone, and a recyclability test confirmed that ~88% of the initial SMX adsorption capacity of nBTC was retained after the fifth adsorption–desorption cycle. Moreover, nBTC presented excellent capacity for the adsorptive removal of bisphenol A from water.

Iron-activated bermudagrass-derived biochar for adsorption of aqueous sulfamethoxazole: Effects of iron impregnation ratio on biochar properties, adsorption, and regeneration

This work focused on the impacts of FeCl3 impregnation ratio on the properties of FeCl3-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m2/g), IA-BCs made via pyrolysis with FeCl3 to BG mass ratio between 1 and 3 (1–3 g FeCl3/g BG) resulted in significantly enhancing surface area (1014–1035 m2/g), hydrophobicity, Fe content in IA-BCs (3.87–7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32–265 mg SMX/g BC) than the control BC (6–14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl3 to BG mass ratio of 2 (IA-BC2.0) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC2.0 over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.

Fabrication of hydrophobic/hydrophilic bifunctional adsorbent for the removal of sulfamethoxazole and bisphenol A in Water

Abstract Powdered activated carbon embedded chitosan-polyvinyl alcohol composite (PAC/CS/PVA) beads were designed via a simple method for the adsorptive removal of hydrophilic sulfamethoxazole (SMX) and hydrophobic bisphenol A (BPA) from water. The as-prepared hydrogel was characterized, and the adsorption performances were comprehensively investigated. The maximum adsorption capacities of SMX and BPA on the adsorbent are 9.1 mg g−1 and 64.6 mg g−1, respectively. The optimal pH was around 4 for SMX and 2–9 for BPA, respectively. Higher adsorbent dosages benefited the removal efficiencies but lowered the adsorption capacities. Both temperature and ionic strength slightly affect the adsorption of SMX and BPA. Pseudo-second-order model can well describe the adsorption of SMX and BPA on the hydrogel through spontaneous and endothermic process. Langmuir isotherm model performed better than Freundlich model to fit the equilibrium data. The stable adsorption capacities of SMX and BPA after used the hydrogel for 5 cycles evidenced its excellent reusability. The high adsorption capacities (> 7 mg g−1 for SMX, > 50 mg g−1 for BPA) in the presence of typical water matrices including Cl−, SO42−, Cu2+ and humic acid further suggest the good application potential of the fabricated PAC/CS/PVA beads.

Chemical Activation of Forage Grass-Derived Biochar for Treatment of Aqueous Antibiotic Sulfamethoxazole.

Chemically activated forage Bermudagrass-derived biochar (A-BC) was produced, characterized, and utilized for adsorption of sulfamethoxazole (SMX) in water for the first time. After NaOH activation, A-BC showed a higher surface area (1991.59 m2/g) and maximum adsorption capacity for SMX (425 mg SMX/g BC) than those of various biochars and commercial activated carbons. The detailed analysis for adsorption of SMX onto A-BC indicated the efficient sorption of SMX through π–π EDA and hydrophobic and hydrogen bond interactions. Additionally, the adsorption of SMX on A-BC was limited by pore and liquid film diffusions. The SMX adsorption on A-BC was found to be endothermic and spontaneous from thermodynamic studies. Furthermore, the highly efficient regeneration of SMX-saturated A-BC over multiple cycles was achieved by NaOH-driven desorption, indicating that the adsorption of SMX onto A-BC would have high potential for cost-effective solution for elimination of SMX from water.

Photocatalytic degradation of sulfonamides by Bi2O3-TiO2/PAC ternary composite: Mechanism, degradation pathway

The photocatalytic degradation of sulfamethoxazole (SMX), sulfadiazine (SDZ) and sulfamethazine (SMT) by Bi2O3-TiO2/PAC under solar light irradiation was studied. The results exhibited that Bi2O3-TiO2/PAC composite prepared by two-stage calcination method contained of rutile and anatase mixed crystal phases, and it had visible light response capability. In addition, Bi2O3-TiO2/PAC had a certain adsorption capacity for SMX, SDZ and SMT, and its saturated adsorption mass was 30.88, 11.28 and 26.24 mg/g, respectively. Compared to photolysis and adsorption process, the photocatalytic degradation efficiencies of the three sulfonamides were significantly improved, and more than 99 % of photocatalytic degradation efficiency was achieved. The EPR measurements showed that both hydroxyl radicals (·OH) and superoxide radicals (·O2−) were produced in the photocatalytic process. However, trapping experiments confirmed that photo-generated hole (h+) played a lead role in the photocatalytic degradation of SMX. Contrarily, the ·O2- was the main oxidative species for SDZ and SMT degradation. Furthermore, the effects of initial pH of solution, sodium bicarbonate, humic acid and natural water (lake and river water) on the photocatalytic degradation were investigated. The photocatalytic degradation pathways of Bi2O3-TiO2/PAC for sulfonamides were discussed. There were differences degradation pathways of the SDZ, SMT and SMX by Bi2O3-TiO2/PAC mainly reflected in: Hydroxylation of benzene ring, extrusion of SO2. While, similar pathways existed in the process of sulfanilamide degradation, such as the breaking of SN bond and the cracking of N-containing benzene ring.

Enhanced adsorption of sulfamethoxazole from aqueous solution by Fe-impregnated graphited biochar

An increasing amount of antibiotics has been released into the aquatic environment and caused a serious threat to public health. In this study, a series of magnetic biochars (MBCs) were prepared via one-step graphitization and magnetization for sulfamethoxazole (SMX) removal. The effects of pyrolysis temperature and impregnated FeCl3 concentration on SMX adsorption were investigated. Characterization of MBC were carried out through SEM, BET, XRD, FTIR, Raman and XPS analyses. The performance for sulfamethoxazole removal was evaluated with the adsorption kinetics and isotherms studies, and the influence of pH, temperature, ion and NOM on SMX adsorption capacity was also examined in batch studies. The results show that the physicochemical properties of the MBCs were dominated by the pyrolysis temperatures and the iron weight ratio. The iron species in MBCs contributed significantly to the enhancement of SMX adsorptive capacity, including increasing the carbonization degree, promoting the formation of oxygen-rich functional groups and providing more adsorption sites. The prepared MBCs was proved to be highly efficient for SMX removal, and the 300-MBC800 was the optimal sorbent with the maximum adsorption capacity of 187.31 mg g−1, which was 5.3 times of the pristine biochar. The primary mechanisms for SMX adsorption include electrostatic interaction, π-π electron-donor-acceptor (EDA) interaction, hydrogen bonding, and Lewis acid-base electron interactions, mainly resulting from the graphitized structures and enriched functional groups on MBCs. This study demonstrated promise of MBC as an effective and environmentally friendly sorbent for removing SMX from wastewater with high adsorption capacity and cost effectiveness.