Adsorption Of Sulfamethoxazole Research Articles

Adsorption of sulfamethoxazole, sulfadiazine and sulfametazine in single and ternary systems on activated carbon. Experimental and DFT computations

In this work the single and ternary removal of sulfonamides (sulfamethoxazole, sulfadiazine and sulfametazine) from water was investigated using granular activated carbon. The single adsorption mechanism was elucidated by obtaining the adsorption isotherms supported by computational calculations. The ternary adsorption was analyzed by using an experimental Box-Behnken type response surface design. The results showed that the total adsorption capacity of activated carbon duplicates in ternary systems compared to single systems. Besides, in both cases the activated carbon showed a greater affinity for removing sulfamethoxazole followed by sulfadiazine and sulfametazine, correspondingly. It was shown that hydrogen bonding interactions presented the highest adsorption energies followed by π-π interactions. From the design of experiments three statistically reliable mathematical models were proposed to estimate the adsorption capacity for each sulfonamide as a function of the solution pH, temperature and initial concentration. Finally, it was shown that sulfonamide ternary adsorption is an endothermic process and that the adsorption rate decreases as a result of partial blockage of the pores due to simultaneous adsorption.

Solution pH affects single, sequential and binary systems of sulfamethoxazole and cadmium adsorption by self-assembled cellulose: Promotion or inhibition?

A new self-assembled cellulose (SACS) containing multi-functional amine, carboxyl and hydroxyl groups was successfully obtained through etherification, cross-linking and grafting processes. Then, the adsorption of sulfamethoxazole (SMZ) and Cd(II) onto SACS at pH values of 3, 5.7 and 7.5 was systematically investigated by batch experiments of single, sequential and binary systems, characterization and density functional theory (DFT) calculations. The presence of Cd(II) decreased the adsorption of SMZ because of hydrophilic site competition, while SMZ inversely increased the adsorption of Cd(II), which was attributed to bridging and especially to electrostatic shielding effects; moreover, both the inhibitory and synergistic effects were more obvious in the binary system and at a pH of 7.5. There was a dynamic balance between the inhibitory and synergistic effects that depended on the system, pH value and concentration ratio. DFT results further indicated that SMZ– more easily coordinated with Cd(II) at sulfonyl oxygen and nitrogen sites, and the cationic bridge of Cd(II) with SMZ– mainly occurred in the sequential system. Moreover, a complexation–decomplexation–complexation balance of SMZ– and Cd(II) probably occurred in the binary system.

Comprehensive evaluation of adsorption performances of carbonaceous materials for sulfonamide antibiotics removal.

Sulfonamide antibiotics have highly toxic effects on humans and other organisms within the food chain. Adsorption by various carbonaceous materials is an effective method for removing them from the aqueous environment. Batch adsorption experiments were conducted between adsorbents and sulfamethoxazole (SMX) by studies of characterization, isotherm model, and kinetic model. The adsorption performances and mechanism of fifteen carbonaceous materials to remove SMX have been comprehensively evaluated. Results of the characterization showed that not only porosity, but also surface chemistry plays an important role in the adsorption process. Changes in the type and quantity of functional groups before and after adsorption are positive for the recyclability of carbonaceous materials. Moreover, kinetic studies showed that the adsorption process followed the pseudo-second-kinetic model and the intra-particle diffusion model. Four adsorbents (i.e., W-GAC, 3M-GAC, GP, and PAC) in this study have the best performance in each corresponding category in terms of the adsorption of SMX. Therefore, the results provide an indispensable reference for evaluating the adsorption performances of a variety of carbonaceous materials, and thus can support the selection of adsorbents for different applications. Graphical abstract.

Machine learning for the selection of carbon-based materials for tetracycline and sulfamethoxazole adsorption

Antibiotics as emerging pollutants have attracted extensive attention due to their ecotoxicity and persistence in the environment. Adsorption of antibiotics on carbon-based materials (CBMs) such as biochar and activated carbon was recognized as one of the most promising technologies for wastewater treatment. This study applied machine learning (ML) methods to develop generic prediction models of tetracycline (TC) and sulfamethoxazole (SMX) adsorption on CBMs. The results suggested that random forest outperformed gradient boosting trees and artificial neural network for both TC and SMX adsorption models. The random forest models could accurately predict the adsorption capacity of antibiotics on CBMs using material properties and adsorption conditions as model inputs. The developed ML models presented better generalization ability than traditional isotherm models under variable environmental conditions (e.g., temperature, solution pH) and adsorbent types. The relative importance analysis and partial dependence plots based on ML models were performed to compare TC and SMX adsorption on CBMs. The results indicated the critical role of specific surface area for both TC (24%) and SMX (45%) adsorption, while the other material properties (e.g., H/C, (O + N)/C, pHpzc) showed variable influences due to the differences in molecular structures, functional groups, and pKa values of TC and SMX. The accurate ML prediction models with generalization ability are useful for designing efficient CBMs with minimal experimental screening, while the relative importance and partial dependence plot analysis can guide rational applications of CBMs for antibiotics wastewater treatment.

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.

Adsorption of sulfamethoxazole and sulfadiazine on phosphorus-containing stalk cellulose under different water pH studied by quantitative evaluation.

To improve the high-value application of corn stalk, phosphorus-containing stalk cellulose (PFC) was prepared, characterized, and utilized for the adsorption of sulfamethoxazole (SMZ) and sulfadiazine (SD), with maximum adsorption capacities of 1.385 and 2.527 mg/g at pH 7. As expected, the adsorption efficiency of PFC was strongly affected by pH, and the preferential adsorption order of SMZ- (SD0) > SMZ0 (SD-) > SMZ+ (SD+) was obtained from the experimental results and due to the charges of PFC and the SMZ and SD species. Furthermore, these results were qualitatively linked to the adsorption mechanism, e.g., π+-π electron donor-acceptor (EDA), anion-π bond electrostatic, and hydrophobic interactions. In particular, the adsorption mechanism was further characterized in terms of structure and analyzed systematically using density functional theory (DFT), frontier orbital theory (FOT), and molecular dynamics (MD) simulation, with the aim to explain the theoretical calculation and experimental results. As a result, the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) orbitals revealed the key role of the rings and functional groups of PFC and SMZ (or SD) and validated the optimized structures of PFC+ sulfonamides (SAs)+, PFC- SAs0, and PFC- SAs-, in which their binding energy values, energy gaps, and relevant molecular lengths determined their stability. Additionally, the van der Waals (vdW) energy confirmed the effect of various interactions on adsorption.

Effect of straw-derived dissolved organic matter on the adsorption of sulfamethoxazole to purple paddy soils

The presence of sulfamethoxazole (SMX) in croplands has become an international concern. The environmental behavior and fate of SMX in agricultural soils are not well understood, especially when the adsorption behavior is disturbed by the dissolved organic matter (DOM) released by crop straw. As canola straw is one of the biomasses widely returned to farmlands, we characterized DOM derived from pristine and decomposed canola straw, and explored the effects and mechanisms of the DOMs on regulating SMX adsorption to purple paddy soils. The spectral analysis showed that the molecular weight, aromaticity, and hydrophobicity of canola straw-derived DOM increased as decomposition proceeded. These physicochemical properties collectively determined the effects of the DOM on SMX adsorption. The DOM derived from pristine canola straw increased SMX maximum adsorption capacity of the soils by approximately 2.6 times, but this positive effect gradually decreased to a steady state by day 90 in the straw decomposition period. Nevertheless, the SMX adsorption behavior in the soils was invariably determined by the DOM extracts. These adsorption processes of SMX were well fitted by the double-chamber kinetics model and the Langmuir and Freundlich thermodynamic models. Thermodynamic parameters indicated that SMX adsorption onto the soils was spontaneous and endothermic, and this adsorption characteristics was not significantly (p > 0.05) changed by the DOM extracts. However, the adsorption kinetics were altered by those DOMs, i.e., the fast and slow adsorption processes were both diminished. Correspondingly, co-adsorption and cumulative adsorption were identified as the main mechanisms determining SMX adsorption to the purple paddy soils in the presence of the straw-derived DOMs. These results collectively indicated that the DOMs released by straw in croplands may decrease the ecological risks of organic pollutants by inhibiting their migration processes.

Degradation of sulfamethoxazole with persulfate using spent coffee grounds biochar as activator

In the present study, biochar from spent coffee grounds was synthesized via pyrolysis at 850 °C for 1 h, characterized and employed as catalyst for the degradation of sulfamethoxazole (SMX) by persulfate activation. A variety of techniques, such as physisorption of N2, scanning electron microscopy, Fourier transform infrared spectroscopy, X–ray diffraction, thermogravimetric analysis, and potentiometric mass titration, were employed for biochar characterization. The biochar has a surface area of 492 m2/g, its point of zero charge is 6.9, while mineral deposits are limited.SMX degradation experiments were performed mainly in ultrapure water (UPW) at persulfate concentrations between 100 and 1000 mg/L, biochar concentrations between 50 and 200 mg/L, SMX concentrations between 500 and 2000 μg/L and initial solution pH between 3 and 10. Real matrices, besides UPW, were also tested, namely bottled water (BW) and treated wastewater (WW), while synthetic solutions were prepared spiking UPW with bicarbonate, chloride, humic acid or alcohols. Almost complete removal of SMX can be achieved using 200 mg/L biochar and 1000 mg/L sodium persulfate (SPS) within 75 min. The presence of biochar is important for the degradation process, while the activity of the biochar increases linearly with SPS concentration. Degradation follows a pseudo–order kinetic model and the rate increases with increasing biochar concentration and decreasing SMX concentration. Although SMX adsorption onto the biochar surface is favored at acidic conditions, degradation proceeds equally fast regardless of the initial solution pH. Reactions in either real matrix are slower, resulting in 55% SMX removal in 60 min for WW. Bicarbonate causes severe inhibition as only 45% of SMX can be removed within 75 min in UPW. The addition of alcohol slightly inhibits degradation suggesting that the reaction pathway is either under electron transfer control or due to the generation of surface oxygen radicals with higher oxidation potential than the homogeneously produced radicals.

Core-Shell Molecularly Imprinted Polymers on Magnetic Yeast for the Removal of Sulfamethoxazole from Water.

In this work, magnetic yeast (MY) was produced through an in situ one-step method. Then, MY was used as the core and the antibiotic sulfamethoxazole (SMX) as the template to produce highly selective magnetic yeast-molecularly imprinted polymers (MY@MIPs). The physicochemical properties of MY@MIPs were assessed by Fourier-transform infrared spectroscopy (FT-IR), a vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), specific surface area (SBET) determination, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out to compare MY@MIPs with MY and MY@NIPs (magnetic yeast-molecularly imprinted polymers without template), with MY@MIPs showing a better performance in the removal of SMX from water. Adsorption of SMX onto MY@MIPs was described by the pseudo-second-order kinetic model and the Langmuir isotherm, with maximum adsorption capacities of 77 and 24 mg g−1 from ultrapure and wastewater, respectively. Furthermore, MY@MIPs displayed a highly selective adsorption toward SMX in the presence of other pharmaceuticals, namely diclofenac (DCF) and carbamazepine (CBZ). Finally, regeneration experiments showed that SMX adsorption decreased 21 and 34% after the first and second regeneration cycles, respectively. This work demonstrates that MY@MIPs are promising sorbent materials for the selective removal of SMX from wastewater.

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.

Three-dimensional porous graphene-like biochar derived from Enteromorpha as a persulfate activator for sulfamethoxazole degradation: Role of graphitic N and radicals transformation

Three-dimensional graphene-like biochar derived from Enteromorpha (EGB) was prepared as a persulfate (PS) activator for sulfamethoxazole (SMX) degradation. The graphitic N in the EGB samples not only endowed the superior binding energy towards SMX adsorption, but also promote the PS binding with the EGB, which was crucial to the catalytic degradation of SMX in EGB/PS system. Different from the radical-based oxidation in biochar prepared at 400 °C via the persistent free radicals (PFRs), both 1O2 and surface electron transfer served as non-radical pathways in the EGB samples prepared above 500 °C, acting together with free radicals (O2∙−) on SMX degradation. Oxidation of SMX and its substructural analogues indicated that the selective oxidizing reaction occurred in the EGB/PS system and the isoxazole ring in SMX molecule was insensitive to be attacked 1O2. In addition, toxicity predication indicated that the overall biotoxicity of the intermediates during SMX degradation was decreased.

A remarkable adsorbent for removal of bisphenol S from water: Aminated metal-organic framework, MIL-101-NH2

Purification of water contaminated with organics has recently attracted much attention. In this study, the adsorptive removal of bisphenol S (BPS) from water was studied by using a metal-organic framework (MOF) MIL-101 with or without –NH2 functionality. In order to understand the adsorption of BPS in detail, adsorption of other relevant materials, such as bisphenol A (BPA) and sulfamethoxazole (SMZ), was also carried out. The adsorbed quantity increased significantly for SMZ and BPS (different from BPA adsorption) with the introduction of –NH2 groups onto MIL-101 even though the surface area of MIL-101-NH2 is much smaller than that of the pristine MIL-101. Moreover, adsorption of BPS was carried out over a wide pH range in order to understand the adsorption mechanism. It could be suggested that hydrogen bonding (with six-membered ring structure) between –S(O)2 and NH2 of MIL-101-NH2 could be an important contribution to the adsorption of BPS and SMZ. Moreover, H-bonding between –NH2 of the MOF and –OH (of BPS and BPA) or –NH2 (of SMZ) might also be possible. SMZ adsorption could remarkably be increased by loading –NH2 on MIL-101, because of another mechanism of ion-dipole interaction between the anionic N of SMZ and the –NH2 of MIL-101-NH2. Finally, MIL-101-NH2 showed the highest adsorption capacity for BPS (513 mg/g, at pH 7), compared with any reported results, and was recyclable after simple ethanol washing, suggesting the possible application of aminated MOFs in the adsorption of organics with sulfonyl group like BPS.

Effect of biochar-derived dissolved organic matter on adsorption of sulfamethoxazole and chloramphenicol

Biochar-derived dissolved organic matter (DOM) plays a crucial role in controlling the interactions between pollutants and biochars. Here, we determined the compositions of DOMs extracting from biochars (BCs) and acid-modified-biochars (MBCs) at different pH using UV, 3D-fluorescence and ultra-high-resolution mass spectroscopy (ESI-FTICR MS), which allowed us, for the first time, to distinguish the effect of DOM from biochars on sulfamethoxazole (SMX) and chloramphenicol (CAP) adsorbed onto biochars. The detailed results showed DOM shortened SMX and CAP adsorption equilibrium time, and more DOM increased SMX adsorbed, while inhibit CAP adsorbed onto biochar. Low-temperature biochar with a high extracting solution pH could release more DOM, and the polarity index of DOM was opposite with corresponding biochar. The correlation between the polarity of biochar and adsorption capacity was opposite to the correlation between the DOM released from corresponding biochars and adsorption capacity. Moreover, we found the fulvic and humic acid-like of DOMs inhibited biochar adsorption for SMX, however, the more compounds fulvic and humic acid-like of DOMs and CcHhOoNnSs molecular structure would promote biochar adsorption of CAP. This study demonstrates the potential of DOM as a new mechanism in adsorption and remediation studies but also reveals challenges for the future application of biochar.

Dynamic Adsorption of Sulfamethoxazole from Aqueous Solution by Lignite Activated Coke.

In this paper, lignite activated coke was used as adsorbent for dynamic column adsorption experiments to remove sulfamethoxazole from aqueous solution. The effects of column height, flow rate, initial concentration, pH and humic acids concentration on the dynamic adsorption penetration curve and mass transfer zone length were investigated. Results showed penetration time would be prolonged significantly by increasing column height, while inhibited by the increasement of initial concentration and flow rate. Thomas and Yoon-Nelson model and the Adams-Bohart model were used to elucidate the adsorption mechanism, high coefficients of R2 > 0.95 were obtained in Thomas model for most of the adsorption entries, which revealed that the adsorption rate could probably be dominated by mass transfer at the interface. The average change rates of mass transfer zone length to the changes of each parameters, such as initial concentration, the column height, the flow rate and pH, were 0.0003, 0.6474, 0.0076, 0.0073 and 0.0191 respectively, revealed that column height may play a vital role in dynamic column adsorption efficiency. These findings suggested that lignite activated coke can effectively remove sulfamethoxazole contaminants from wastewater in practice.

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.

Carbon nanotube supported sludge biochar as an efficient adsorbent for low concentrations of sulfamethoxazole removal

A novel adsorbent of sludge biochar (SBC) and multi-walled carbon nanotube (CNT) composite was synthesized (CNT-SBC) to remove low concentrations of sulfamethoxazole (SMX) from water. The key factors of dose, contact time, pH and temperature were investigated. Higher dose of adsorbents provided more active sites for SMX adsorption. The effect of pH was due to the electrostatic interaction. Increasing the temperature was beneficial to SMX adsorption, which was a spontaneous endothermic process and the strength of the spontaneous increased with CNT supporting. As pseudo-second-order, Elovich, Langmuir and Freundlich models fitted the experimental data better, this suggested that both physisorption and chemisorption played vital roles during the adsorption process. In addition, liquid film diffusion was the main rate-limiting step of adsorption. Compared with SBC (5.43 × 103 μg g−1), CNT-SBC-1 (CNT:SBC = 1:2), CNT-SBC-2 (CNT:SBC = 1:4) and CNT-SBC-3 (CNT:SBC = 1:6) exhibited better adsorption performance with up to 2.35 × 104, 1.49 × 104 and 1.22 × 104 μg g−1 at 25 °C, respectively. The characterization analysis demonstrated that the stronger adsorption capacity of CNT-SBC was mainly attributed to the pore filling, functional groups complexation and π-π interaction. In summary, as an efficient and environment-friendly adsorbent, CNT-SBC has promising potential for low concentrations of SMX and other emerging contaminants removal from water.

Highly efficient adsorptive removal of sulfamethoxazole from aqueous solutions by porphyrinic MOF-525 and MOF-545

The metal-organic frameworks MOF-525 and MOF-545 comprised of Zr-oxide clusters and porphyrin moieties in different geometries were synthesized solvothermally and applied for the adsorptive removal of the broadly used organic contaminant sulfamethoxazole (SMX) from water. Both MOFs were found highly efficient for the adsorption of SMX with the maximum adsorption capacities of 585 and 690 mg/g for MOF-525 and MOF-545, respectively. The latter value is the highest adsorption capacity reported so far for the adsorption of SMX molecules on any adsorbent. The adsorption equilibrium could be modeled successfully by the Langmuir model, which showed close to matching with the experimental data. Their adsorption equilibriums were attained within 120 and 30 min for MOF-525 and MOF-545, respectively. MOF-545 with mesopores demonstrated superior adsorption kinetics to MOF-525 with micropores, and the simulation by the pseudo-second-order kinetic model indicated ca. 20 times faster adsorption by MOF-545 than MOF-525. Both showed pH-dependent adsorption of SMX with a gradual reduction at high pH due to the repulsion between negatively charged adsorbent and SMX. The adsorption of SMX conducted over a group of representative MOFs with different physicochemical properties and detailed characterization confirmed that the high adsorption capacity of the porphyrin MOFs is achieved by H-bonding between the SMX molecule and the N-sites of the porphyrin units in the MOFs, π-π interaction, and the high surface area. The adsorbents were easily regenerated by simple washing with acetone and reusable with >95% efficiency during 4 repeated adsorption-desorption cycles.

Super-magnetization of pectin from orange-peel biomass for sulfamethoxazole adsorption

In recent decades, the release of emerging pharmaceutical contaminants has been recognized as a challenging environmental issue. This study focuses on the adsorption of sulfamethoxazole (SMX) by pectin (Pec)-based bio-adsorbent. Pec was extracted from orange peel-waste biomass (OPB) by a microwave-assisted extraction method. Further, different concentrations of Pec from OPB (Pec-OPB); 0.5, 1, 2 and 4g were super-magnetized with Fe3O4 nanoparticles (denoted as Fe3O4@Pec-OPB(0.5g), Fe3O4@Pec-OPB(1g), Fe3O4@Pec-OPB(2g) and Fe3O4@Pec-OPB(4g), respectively). Among these synthesized bio-adsorbents, Fe3O4@Pec-OPB(1g) gave significant SMX adsorption and hence studied further in detail. Surface-morphology, structure, functional-groups, magnetic-property, and elemental-composition of facile of Fe3O4@Pec-OPB(1g) was characterized by standard analytical techniques. Different parameters for SMX adsorption on Fe3O4@Pec-OPB(1g) were investigated, such as optimal pH (4.0), kinetics (best-fitted pseudo-second-order kinetic model) and isotherm models (best-fitted Redlich-Peterson model). The maximum adsorption capacity (qm) of Fe3O4@Pec-OPB(1g) was 120 mg g−1 of SMX. Thermodynamic analysis corroborated the endothermic nature of the adsorption process. Therefore, the nano-bio-adsorbent Fe3O4@Pec-OPB(1g) exhibits excellent potential for capturing the SMX from water, suggesting that Fe3O4@Pec-OPB(1g) could be a viable option for adsorptive reclamation of hazardous cationic pollutants from water.