Adsorption Of Sulfonamides Research Articles

Implications of polystyrene and polyamide microplastics in the adsorption of sulfonamide antibiotics and their metabolites in water matrices

Microplastics (MP) and antibiotics coexist in the environment and their combined exposure represents a source of increasing concern. MP may act as carriers of antibiotics because of their sorption capacity. Knowledge of the interactions between them may help improve understanding of their migration and transformation. In this work, the adsorption behaviour of a group of sulfonamides and their acetylated metabolites on different sizes of polyamide (PA) and polystyrene (PS) MP were investigated and compared. Sulfonamides were adsorbed on both MP (qmax up to 0.699 and 0.184 mg/g, for PA and PS, respectively) fitting to a linear isotherm model (R2 > 0.835). A low particle size and an acidic and salinity medium significantly enhances the adsorption capacity of sulfonamides (i.e. removal of sulfamethoxazole increased from 8 % onto 3 mm PA pellets to 80 % onto 50 mm of PA pellets). According to characterization results, adsorption mechanism is explained by pore filling and hydrogen bonds (for PA) and hydrophobic interactions (for PS). After adsorption, surface area was increased in both MP as result of a potential ageing of the particles and the intensity of XRD peaks was higher denoting a MP structure more amorphized. Metabolites were adsorbed more efficiently than their parent compounds on PS while the opposite effect was observed on PA explained by the acetylation of the amine group and, subsequently the reduction of hydrogen bond interactions. Although the dissolved organic matter inhibits sulfonamides adsorption, removal up to 65.2 % in effluent wastewater and up to 72.1 % in surface water were observed in experiments using real matrices denoting the role of MP as vectors of sulfonamide antibiotics in aquatic media.

A review on carbon-based biowaste and organic polymer materials for sustainable treatment of sulfonamides from pharmaceutical wastewater.

Frequent detection of sulfonamides (SAs) pharmaceuticals in wastewater has necessitated the discovery of suitable technology for their sustainable remediation. Adsorption has been widely investigated due to its effectiveness, simplicity, and availability of various adsorbent materials from natural and artificial sources. This review highlighted the potentials of carbon-based adsorbents derived from agricultural wastes such as lignocellulose, biochar, activated carbon, carbon nanotubes graphene materials as well as organic polymers such as chitosan, molecularly imprinted polymers, metal, and covalent frameworks for SAs removal from wastewater. The promising features of these materials including higher porosity, rich carbon-content, robustness, good stability as well as ease of modification have been emphasized. Thus, the materials have demonstrated excellent performance towards the SAs removal, attributed to their porous nature that provided sufficient active sites for the adsorption of SAs molecules. The modification of physico-chemical features of the materials have been discussed as efficient means for enhancing their adsorption and reusable performance. The article also proposed various interactive mechanisms for the SAs adsorption. Lastly, the prospects and challenges have been highlighted to expand the knowledge gap on the application of the materials for the sustainable removal of the SAs.

ZIF-8 templated mesoporous triazine covalent-organic polymer for adsorptive removal of sulfonamides from water

A highly porous covalent-organic polymer with mesoporosity (named MT-MCTP) was prepared for the first time via ZIF-8 (a zeolitic imidazolate framework, comprised of ZnN4 tetrahedral units interconnected by methyl imidazolate linkers) templated synthesis of microporous triazine polymer (MCTP) and subsequent removal of ZIF-8. MT-MCTP had higher porosity and wider pore size than the conventional MCTP. The prepared MT-MCTP, together with MCTP and commercial activated carbon (AC), was applied to the adsorptive elimination of sulfonamides like sulfamethoxazole and sulfachlorpyridazine from water. MT-MCTP showed the highest kinetic constants among the three adsorbents in the sulfonamides adsorption because of the developed mesopores obtained with the sacrificial ZIF-8 template. Additionally, the adsorbed amounts of sulfamethoxazole and sulfachlorpyridazine over the adsorbents decreased in the order: MT-MCTP > MCTP > AC. MT-MCTP had a maximum adsorption capacity (Q0) of 557 and 534 mg/g for sulfamethoxazole and sulfachlorpyridazine, respectively, which are much higher than the capacity observed with AC. Importantly, MT-MCTP is a recyclable adsorbent with the highest Q0 for sulfamethoxazole compared with any reported results, so far, in near-neutral conditions. Based on the adsorption and surface charge under wide pH ranges, the noticeable sulfamethoxazole adsorption over MT-MCTP could be interpreted with the favorable pore structure (mesopore), surface charge, π–π interaction, and hydrogen bonding interaction.

The effects of UiO-66 ultrafine particles on the rapid detection of sulfonamides in milk: Adsorption performance and mechanism.

Nanoscale MOFs particles possess both excellent adsorption and dispersion properties. In this study, ultrafine particles UiO-66 (UP/UiO-66) with a particle size below 50nm were synthesised by a template-controlled method. UP/UiO-66 was able to achieve a maximum adsorption capacity of 139.64mg/g for 5 methoxylated sulfonamides. Adsorption studies showed that UP/UiO-66 adsorption of sulfonamides can be classified as a pseudo-secondary kinetic adsorption model for single molecular layer adsorption. ELISA (validated by Raman and molecular docking) showed that the sulfonamide molecule was still immunoreactive with antibodies after adsorption by UP/UiO-66. In 15min, UP/UiO-66 could be used directly in the ELISA test for sulfonamides in milk without elution and separation. The LOQ (IC20) of UP/UiO-66-ELISA for sulfonamides in milk was 0.21-2.05ng/mL. The ultrafine particle strategy of UiO-66 is expected to be applied to other MOFs and used as a general pretreatment material for residue monitoring in complex matrices.

Adsorption of sulfonamides on polyamide microplastics in an aqueous solution: behavior, structural effects, and its mechanism

Although microplastics (MPs) and sulfonamides (SAs) are emerging aquatic pollutants, the structural effects of SAs following their adsorption on MPs and underlying mechanisms of the same remain unelucidated. In this study, the characteristics of the adsorption of 10 SAs on polyamide (PA) were analyzed, and significant structural effects of the former were observed at different pH values (P < 0.01). The highest adsorption distribution coefficient (Kd) was ∼7.83–43.57 times the lowest one. The key processes and micromechanisms of SA adsorption on PA were revealed using the quantitative structure–activity relationship model and partial least squares structural equation model (PLS-SEM). The results suggest that both the octanol–water partition coefficients (Kow) of SAs and the valid adsorption energies (Ead-v) between PA and SAs are vital in the observed structural effects of SAs. Furthermore, the density functional theory results demonstrated that during the adsorption of SAs on PA, the different adsorption energies were engendered by equilibrium configurations and interactions, such as hydrophobic, hydrogen bond (H-bond), van der Waals, and electrostatic interactions. Moreover, the developed PLS-SEM models revealed that during the adsorption of cationic (PA–SA+) and anionic (PA–SA−) SAs, the structural effects were partially driven by the electrostatic interactions. Conversely, the structural effects of neutral SA (SA0) adsorption on PA were partially due to H-bond interactions. Overall, we pioneered a theoretical basis to understand the structural effects of SAs following their adsorption on MPs.

Enhanced Adsorption of Sulfonamides by Attapulgite-Doped Biochar Prepared with Calcination.

The extensive use of sulfonamides seriously threatens the safety and stability of the ecological environment. Developing green inexpensive and effective adsorbents is critically needed for the elimination of sulfonamides from wastewater. The non-modified biochar exhibited limited adsorption capacity for sulfonamides. In this study, the attapulgite-doped biochar adsorbent (ATP/BC) was produced from attapulgite and rice straw by calcination. Compared with non-modified biochar, the specific surface area of ATP/BC increased by 73.53−131.26%, and the average pore width of ATP/BC decreased 1.77−3.60 nm. The removal rates of sulfadiazine and sulfamethazine by ATP/BC were 98.63% and 98.24%, respectively, at the mass ratio of ATP to rice straw = 1:10, time = 4 h, dosage = 2 g∙L−1, pH = 5, initial concentration = 1 mg∙L−1, and temperature = 20 °C. A pseudo-second-order kinetic model (R2 = 0.99) and the Freundlich isothermal model (R2 = 0.99) well described the process of sulfonamide adsorption on ATP/BC. Thermodynamic calculations showed that the adsorption behavior of sulfonamides on the ATP/BC was an endothermic (ΔH > 0), random (ΔS > 0), spontaneous reaction (ΔG < 0) that was dominated by chemisorption (−20 kJ∙mol−1 > ΔG). The potential adsorption mechanisms include electrostatic interaction, hydrogen bonding, π−π interaction, and Lewis acid−base interactions. This study provides an optional material to treat sulfonamides in wastewater and groundwater.

Decipher the molecular descriptors and mechanisms controlling sulfonamide adsorption onto mesoporous carbon: Density functional theory calculation and partial least-squares path modeling

Mesoporous carbons (MCs) exhibit excellent removal efficiencies to various organic chemicals. However, how the properties of chemicals influence the adsorption mechanisms and further determine their adsorption onto MCs are poorly understood. We investigated the adsorption of 22 sulfonamides (SAs) onto four MCs, and further uncovered the major molecular descriptors and adsorption mechanisms influencing the adsorption by density functional theory (DFT) and partial least-squares path modeling (PLS-PM). The results revealed that the excess molar refraction (E), McGowan’s molar volume (V), energy of the highest occupied molecular orbital (EHOMO), hardness (H), and most positive net charge on carbon atom (Qc+) were identified as the indirect factors affecting the distribution coefficient (logKD), by influencing the BE(π-π), BE(H), and logKow. BE(π-π) and logKow displayed significant direct impacts on logKD (p < 0.05), while BE(H) showed insignificant direct influences on logKD (p > 0.05). The PLS-PM results indicate the main driving forces for SAs adsorption including π-π interactions, hydrophobic effects, and hydrogen bonding. This study provides a new perspective on revealing the adsorption mechanisms, and the identified factors can be used to develop the quantitative model to further predict the adsorption of SAs onto MCs.

Metal-organic framework modified carbon cloth for electric field enhanced thin film microextraction of sulfonamides in animal-derived food

Sulfonamides (SAs) were widespread in animal-derived food at trace level, which could trigger hazards to human health. Herein, electric field enhanced thin-film microextraction (EE-TFME) was developed based on carbon cloth (CC) modified with metal-organic frameworks (MOFs) for extraction of SAs (sulfadiazine, sulfathiazole, sulfamerazine, sulfadimidine, sulfamethoxazole and sulfisoxazole), which were a series of polar analytes. MIL-101(Cr) was in situ synthesized on CC via hydrothermal reaction and then was used as positive electrode in EE-TFME for adsorption of SAs. Compared with traditional TFME, EE-TFME shortened extraction equilibrium time from 30 min to 15 min. Coupled with high-performance liquid chromatography (HPLC), the limits of detection (LODs) were 2.5–4.5 µg/L, while the repeatability and intermediate precision was lower than 9.1%. Quantitative determination of SAs in extracts of animal-derived samples, such as honey, pork, chicken and milk, was achieved with recoveries from 81.7% to 114.2%. The developed MOF/CC-based EE-TFME has a great potential in rapid extraction of similar polar or ionic analytes from complex food matrices.

Response of fungi-microalgae pellets to copper regulation in the removal of sulfonamides and release of dissolved organic matters

Both sulfonamides (SAs) and copper (Cu(II)) were frequently detected together in swine wastewater. In this study, the regulation of Cu(II) on SAs adsorption and release of dissolved organic matters (DOMs) by fungi-microalgae pellets (FM-pellets) were investigated. Aspergillus oryzae pellets were prepared for combination with Chlorella vulgaris and the optimal conditions were at agitation speed of 130 rpm, fungi to microalgae ratio of 10:1 and the combined time of 3 h with the highest combination efficiency of 98.65%. The results showed that adsorption was the main mechanism for SAs removal. FM-pellets exhibited a high SAs adsorption potential within 6 h, and the adsorption capacity of sulfamethazine (SMZ), sulfamonomethoxine (SMM) and sulfamethoxazole (SMX) was 1.07, 0.94 and 1.67 mg/g, respectively. Furthermore, the removal of SMX, SMZ and SMM was greatly promoted from 62.31% to 85.21%, 58.71–67.91% and 64.17–80.31%, respectively, under the presence of 2 mg/L Cu(II) through ion exchange and adsorption bridging. DOMs were analyzed by the parallel factor (PARAFAC) to demonstrate the response mechanism of FM-pellets to Cu(II). Protein-like substances and NADH in DOMs released by FM-pellets formed complexes with Cu(II) to alleviate the damage on the organism. These findings provide new insights into the mechanism and response of Cu(II) in the removal of SAs by FM-pellets.

A magnetic molecularly imprinted polymer hierarchical composite adsorbent embedded with a zinc oxide carbon foam nanocomposite for the extraction of sulfonamides

A hierarchical composite adsorbent incorporated a nanocomposite of zinc oxide and carbon foam embedded in a magnetic molecularly imprinted polymer (ZnO@CF@Fe3O4-SiO2-NH2@MIP). The adsorbent was used to extract, preconcentrate and determine sulfonamides. The fabricated adsorbent was characterized, the fabrication and extraction conditions were investigated and the extracted sulfonamides were determined using high performance liquid chromatography. The zinc oxide carbon foam nanocomposite helped to improve the adsorption of sulfonamides. The MIP provided highly specific recognition cavities for three sulfonamides and the magnetic material enabled the simple and rapid separation of the adsorbent after adsorption and desorption. Under optimum conditions, the developed strategy provided a good linearity from 2.0 to 150.0 μg L-1 with R2 better than 0.995. The LOD and LOQ were 2.0 and 5.0 μg L-1, respectively. The developed strategy determined sulfonamides in milk and water with extraction recoveries between 84.3 and 96.2% and RSDs lower than 7%. Concentrations of sulfadiazine were found in some milk and water samples at 2.50 and 2.05 μg L-1, respectively. The advantages of the developed nanocomposite adsorbent are high specificity and extraction efficiency, simplicity and convenience, and good stability that enables reuse.

Covalent-organic polymer-derived carbons: An effective adsorbent to remove sulfonamide antibiotics from water

A new mesoporous N-doped carbonaceous material was prepared for the first time from a microporous triazine polymer (MCTP) (a covalent-organic polymer) by high-temperature pyrolysis after loading Zn(OH)2. The material, denoted ZCDC, was successfully applied for the adsorptive removal of sulfonamides like sulfamethoxazole (SMX) and sulfachlorpyridazine (SCP) from aqueous solutions. ZCDC showed better performance compared with the carbon prepared from MCTP only (without loading Zn(OH)2) due to the increased mesoporosity. The kinetic studies indicated that a practical equilibrium on ZCDC adsorption can be achieved within 1 h and 4 h for SMX and SCP, respectively. The adsorption isotherms can be fitted with the Langmuir adsorption model and one ZCDC, ZCDC(10), had a maximum adsorption capacity (Q0) of 514 and 430 mg/g for SMX and SCP (at pH 7.0), respectively. Moreover, the ZCDC(10) ranked the third position (with a Q0 value of 514 mg/g), after N-doped beta zeolite-derived carbon and MOF-545, in SMX adsorption. Based on the adsorption and surface charge under wide pH ranges, the adsorption could be attributed to the favorable pore structure, π–π, and H-bonding interactions. The ZCDC(10), showing the excellent performance in sulfonamides adsorption, was easily regenerated by washing with acetone for up to five adsorption-desorption cycles.

Adsorption of Sulfonamides in Aqueous Solution on Reusable Coconut-Shell Biochar Modified by Alkaline Activation and Magnetization.

Biochar is a low-cost adsorbent for sorptive removal of antibiotics from wastewater, but the adsorption efficiency needs to be improved. In this study, coconut-shell biochar was activated with KOH to improve the adsorption efficiency and magnetically modified with FeCl3 to enable recycling. The amount of KOH and the concentration of FeCl3 were optimized to reduce the pollution and production cost. The KOH-activated and FeCl3-magnetized biochar gave good sulfonamide antibiotic (SA) removal. The maximum adsorption capacities for sulfadiazine, sulfamethazine and sulfamethoxazole were 294.12, 400.00 and 454.55 mg g−1, respectively, i.e., five to seven times higher than those achieved with raw biochar. More than 80% of the adsorption capacity was retained after three consecutive adsorption-desorption cycles. A combination of scanning electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, Fourier-transform infrared and Raman spectroscopies, and magnetic hysteresis analysis showed that KOH activation increased the specific surface area, porosity, and number of oxygen-rich functional groups. Iron oxide particles, which were formed by FeCl3 magnetization, covered the biochar surface. The SAs were adsorbed on the modified biochar via hydrogen bonds between SA molecules and -OH/-COOH groups in the biochar. Investigation of the adsorption kinetics and isotherms showed that the adsorption process follows a pseudo-second-order kinetic model and a monolayer adsorption mechanism. The adsorption capacity at low pH was relatively high because of a combination of π+-π electron-donor-acceptor, charge-assisted hydrogen-bonding, electrostatic, and Lewis acid-base interactions, pore filling, van der Waals forces and hydrophobic interactions. The results of this study show that magnetically modified biochar has potential applications as an effective, recyclable adsorbent for antibiotic removal during wastewater treatment.

Adsorption of sulfonamides from aqueous solution by carbon nanotubes: determination of kinetics, equilibrium and thermodynamic parameters

Adsorption of sulfonamides from aqueous solution by carbon nanotubes: determination of kinetics, equilibrium and thermodynamic parameters

Growth of MOF@COF on corncob as effective adsorbent for enhancing adsorption of sulfonamides and its mechanism

MOF@COF composite was fabricated for greater adsorption capacity through the utilization of corncob, which is a natural, sustainable, and cellulose-rich resource. An in-situ growth strategy was implemented to graft UiO-66-NH2 on carboxyl-terminal corncob induced by the thermal esterification of critic acid. Subsequently, corncob@UiO-66-NH2@TpBD was constructed through the Schiff base reaction between 2,4,6-triformylphloroglucinol (Tp) and UiO-66-NH2 as well as benzidine (BD). The ratio of UiO-66-NH2 and TpBD was optimized to be 5:3 for enhancing adsorption capacity. Based on the π-π, hydrogen bonding, and -SO2-Zr-O- coordination effect, sulphonamides (SAs) were chosen to investigate the adsorption capacity of adsorbent using an in-syringe solid phase extraction (IS-SPE) method. The binding energy calculated using density functional theory (DFT) reached −37.45 Kcal/mol, which indicated the strong interactions between SAs and corncob@UiO-66-NH2@TpBD. Combined with ultra-performance liquid chromatography (UPLC), a high sensitivity was obtained with low detection of 0.10 μg/L. The prepared corncob@UiO-66-NH2@TpBD exhibited good reproducibility within relative standard deviations (RSDs) 3.1%-3.4% in intra-batch and 4.3%-8.4% in inter-batch. Moreover, the extraction capacity of adsorbent was not decreased in 20 recycles adsorption–desorption within RSDs 3.8%-8.5%. With features of permanent porosity, multiple active sites, and good renewability, corncob@UiO-66-NH2@TpBD shows great potential towards industrial applications in the field of adsorption.

Contrasting effects of microplastic aging upon the adsorption of sulfonamides and its mechanism

The aging behavior of microplastics (MPs) is unavoidable in the natural environment, but the mechanisms underlying the differences in MP aging affecting the adsorption performance of different MPs remain unclear. In this work, the adsorption characteristics of sulfonamides (SAs) on virgin MPs (thermoplastic polyurethanes (TPUs), polyamides (PAs)) and aged MPs were determined under simulated conditions (ultraviolet (UV), ultraviolet combined hydrogen peroxide (UV + H2O2)). Contrasting effects of MP aging on SA adsorption were observed. That is, the adsorption capacities of aged PAs were decreased from 14.45% to 58.53%, whereas those of aged TPUs were increased from 13.93% to 171.30%. To interpret this interesting phenomenon, the structural characteristics of the tested MPs were determined, and the results indicated that the surface structures of MPs changed with aging, which resulted in differences in hydrophobicity and surface charge and a significant difference in the concentrations of oxygen-containing functional groups (P < 0.05). Furthermore, density functional theory (DFT) results revealed that the equilibrium configurations and the interactions (H bond, electrostatic effect, van der Waals (vdW) forces were significantly influenced by the change in the concentration of oxygen-containing functional groups of MPs (P < 0.05), with the strength of H bonds increasing for aged TPUs-SAs and the strength of electrostatic interactions decreasing for aged PA-SAs. Our findings are the first to provide a theoretical basis for an improved understanding of the role of aging in SAs adsorption onto MPs.

Adsorption behavior of Cd (II) on TEMPO-oxidized cellulose in inorganic/ organic complex systems

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) was oxidized to produce TEMPO-oxidized cellulose (TOCS) with a nanofunctionalized surface and abundant carboxyl groups. In a batch experiment, three pH values (2, 5 and 7), three modes (single, binary and multiple systems), and systems with inorganic and organic materials were applied to explore the adsorption of coexisting metals and antibiotics on TOCS. The adsorption capacity of TOCS was substantially influenced by these factors, and the adsorption behaviors were also different in these systems. In general, the coordination behaviors and electrostatic attraction between Cd(II) and carboxyl groups were identified as the mechanism employed by the single system, while hydrophobic interactions, π interactions, hydrogen bonding and pore filling contributed to the adsorption of sulfonamides (SAs) on TOCS in the binary system. The bridging effect was determined to be the key mechanism; i.e., most Cd(II) and SAs in the form of [SA-Cd] complexes interacted with carboxyl groups, especially in the presence of high concentrations of Cd(II) and SAs. These adsorption behaviors were determined quantitatively by performing density functional theory (DFT) calculations. In addition, TOCS showed excellent adsorption capacity in a more complex interference system, and the maximum adsorption capacity was 5.83 mg/g.

Sulfonamide antibiotics in groundwater and their migration in the vadose zone: A case in a drinking water resource

Vadose zone is an important channel for sulfonamide contamination into groundwater, and the processes of adsorption and migration in the vadose zone are complicated. In this study, we focused on three sulfonamide antibiotics (sulfamethoxazole, sulfamethazine and sulfamethoxypyridazine) in the groundwater of Limin drinking water resource in northeastern China and assessed their migration potential in aquifers. Analysis was based on adsorption batch tests, a column experiment. Some key influencing factors including pH, iron, manganese and ammonia were considered. The results showed that the concentration of sulfamethoxypyridazine in groundwater is higher, ranging between 7 and 30 ng/L, the concentrations of sulfamethoxazole and sulfamethazine are relatively lower and no more than 1 ng/L. The adsorption capacity of the three antibiotics on vadose zone materials shows the following order: sulfamethoxypyridazine > sulfamethazine > sulfamethoxazole. Furthermore, for the three sulfonamides, the adsorption is higher in the medium of 0–20 cm (finer particle size, higher clay content and lower sand content) than that in 80–100 cm. Coexisting ions (iron, manganese and ammonia) promote the adsorption of sulfonamides, and the adsorption of sulfonamides decreases as the water pH increases. The column experiment also shows that the three sulfonamides have strong migration abilities and pose a considerable risk to groundwater.

Adsorption of sulfonamides to marine diatoms and arthropods

Sulfonamides are frequently detected in the environment, where these compounds adsorb to soil particles and are retained in the environment. However, adsorption of sulfonamides to planktonic particles in the sea is not known. Here we demonstrate that sulfonamides adsorb to a diatom (Chaetoceros) and an arthropod (Artemia), albeit at low levels, under laboratory conditions. In both plankton, sulfamethazine (SMT) was more readily adsorbed than was sulfamethoxazole (SMX). The adsorption occurred quickly and the concentration on the plankton was stable for at least 24 h (Chaetoceros) or 5 h (Artemia). These data suggest that marine plankton may retain sulfonamides, although the adsorbed concentration per cell or individual is not high.

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.

Adsorption of sulfonamides on biochars derived from waste residues and its mechanism

Waste residues have been prepared as biochar (BC) adsorbents to remove sulfonamides (SAs) at low cost, but the mechanisms of the differences in the SA adsorption performance of different BCs are not clear. Thus, the adsorption characteristics of two SAs (sulfadiazine and sulfathiazole) on three BCs derived from waste residues (sewage sludge (SB), pig manure (PB), and rice straw (RB)) were investigated. The results showed that the adsorption mechanism was chemisorption and RB was the preferred BC under the different tested conditions (pH, Ca2+, and humic acid), followed by PB and SB. To interpret the phenomena, FTIR, XRD, and XPS analyses were performed and results indicated that SB had the lowest C content, and there was a very significant difference in the concentrations of the two O functional groups (C˭O and C‒O) for PB and RB (P < 0.01). Density functional theory calculations revealed that the mechanisms of SA adsorption onto BCs were mainly through π–π electron donor acceptor interactions and H bonds. There was no significant difference in the π interactions between the SAs-BC containing C‒O (BC(OH)) and the SAs-BC containing C˭O (BC(C˭O)), whereas the H bond strength of SAs-BC(OH) was much stronger than that of SAs-BC(C˭O).