Efficient removal of oxytetracycline from aqueous solution using magnetic montmorillonite-biochar composite prepared by one step pyrolysis

Adsorptive removal of oxytetracycline hydrochloride using bagasse-based biochar powder and beads

Oxytetracycline Hydrochloride (OTC), a common antibiotic used to treat specific illnesses in humans and animals, is characterized by poor absorption into cells, low volatility, and high hydrophilicity. It is a potent contaminant that poses a serious threat to the ecosystem, particularly the aquatic sources. Adsorption onto natural adsorbents is one of the most successful, economical, and ecologically friendly ways to remove antibiotics from waste water. The present work focuses on the adsorption of OTC utilizing alginate biochar beads (AlBCB) and biochar powder (BC) derived from bagasse. The influence of several factors were studies and optimized through batch studies employing BC and AlBCB. After 50 min BC displayed a removal of 97%, at an initial concentration of 10 ppm. The experimental data was discovered to follow PFO kinetics and fit with the Freundlich isotherm adsorption model. AlBCB, after a contact time of 40 min, indicated a maximum percentage removal of 86% for initial concentration of 10 ppm OTC. Al-biochar beads showed the maximum percentage removal at pH 10. 0.5 g of adsorbent was used to carry out all batch experiments at room temperature. The adsorption fitted Freundlich adsorption isotherm and intraparticle diffusion kinetics.

Removal of oxytetracycline from pharmaceutical wastewater using kappa carrageenan hydrogel

This study investigated the adsorption of Oxytetracycline (OTC) from pharmaceutical wastewater using a kappa carrageenan based hydrogel (KPB). The aim of the present study was to explore the potential of KPB for long-term pharmaceutical wastewater treatment. A sustainable adsorbent was developed to address oxytetracycline (OTC) contamination. The hydrogel's structural and adsorption characteristics were examined using various techniques like Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-ray powder diffraction (XRD), and kinetic models. The results revealed considerable changes in the vibrational modes and adsorption bands of the hydrogel, suggesting the effective functionalization of Bentonite nano-clay. Kappa carrageenan based hydrogel achieved the maximum removal (98.5%) of OTC at concerntration of 40 mg/L, pH 8, cotact time of 140 min and adsorbent dose of 0.1 g (KPB-3). Adsorption of OTC increased up to 99% with increasing initial concentrations. The study achieved 95% adsorption capacity for OTC using a KPB film at a concentration of 20 mg/L and a 0.1 g adsorbent dose within 60 min. It also revealed that chemisorptions processes outperform physical adsorption. The Pseudo-Second-Order model, which emphasized the importance of chemical adsorption in the removal process, is better suited to represent the adsorption behavior. Excellent matches were found that R2 = 0.99 for KPB-3, R2 = 0.984 for KPB-2 and R2 = 0.989 for KPB-1 indicated strong chemical bonding interactions. Statisctical analysis (ANOVA) was performed using SPSS (version 25) and it was found that pH and concentration had significant influence on OTC adsorption by the hydrogel, with p-values less than 0.05. The study identified that a Kappa carrageenan-based hydrogel with bentonite nano-clay and polyvinyl alcohol (PVA) can efficiently remove OTC from pharmaceutical effluent, with a p-value of 0.054, but weak positive linear associations with pH, temperature, and contact time. This research contributed to sustainable wastewater treatment and environmental engineering.

Synergistic interactions and reaction mechanisms of biochar surface functionalities in antibiotics removal from industrial wastewater

Biochar, a carbon-rich material with a unique surface chemistry (high abundance of surface functional groups, large surface area, and well-distributed), has shown great potential as a sustainable solution for industrial wastewater treatment as compared to conventional industrial wastewater treatment techniques demand substantial energy consumption and generate detrimental byproducts. This critical review emphasizes the surface functionalities formation and development in biochar to enhance its physiochemical properties, for utilization in antibiotics removal. Factors affecting the formation of functionalities, including carbonization processes, feedstock materials, operating parameters, and the influence of pre-post treatments, are thoroughly highlighted to understand the crucial role of factors influencing biochar properties for optimal antibiotics removal. Furthermore, the research explores the removal mechanisms and interactions of biochar-based surface functionalities, hydrogen bonding, encompassing electrostatic interactions, hydrophobic interactions, π-π interactions, and electron donor and acceptor interactions, to provide insights into the adsorption/removal behavior of antibiotics on biochar surfaces. The review also explains the mechanism of factors influencing the removal of antibiotics in industrial wastewater treatment, including particle size and pore structure, nature and types of surface functional groups, pH and surface charge, temperature, surface modification strategies, hydrophobicity/hydrophilicity, biochar dose, pollutant concentration, contact time, and the presence of coexisting ions and other substances. Finally, the study offers reusability and regeneration, challenges and future perspectives on the development of biochar-based adsorbents and their applications in addressing antibiotics. It concludes by summarizing the key findings and emphasizing the significance of biochar as a sustainable and effective solution for mitigating antibiotics contamination in industrial wastewater.

Transport and release behaviors of PFOA in saturated and unsaturated porous media with biochar amendment

The widespread usage of perfluorooctanoic acid (PFOA) in daily consumer products and its high mobility in porous media have resulted in ubiquitous contamination of PFOA in the natural environment. Developing techniques to immobilize and inhibit the transport of PFOA thus is critical to reduce its potential risks. In present study, biochar, one type of environmental-friendly material produced from cellulose, was utilized in porous media to test its addition on inhibiting the transport and release of PFOA before and after aging process. We found that although PFOA had high mobility in saturated/unsaturated porous media, biochar addition could significantly inhibit PFOA transport in porous media with different saturations due to its high adsorption capacity towards PFOA. The inhibited transport of PFOA by biochar also held true in solution with copresence of natural organic matter and in actual river water. Moreover, we found that negligible PFOA was released from porous media with biochar amendment even after exposure to freeze-thaw/dry-wet treatment. PFOA adsorbed onto biochar could be completely desorbed and the biochar could be reused for subsequent cycles after desorption. Clearly, amendment of porous media with biochar would be a feasible and cost-effective method to immobilize PFOA in natural environment and reduce its environmental risks.

Cellulose nanocrystals intercalated clay biocomposite for rapid Cr(VI) removal

The application of bentonite (Bt) as an adsorbent for heavy metals has been limited due to its hydrophobicity and insufficient surface area. Herein, we present cellulose nanocrystal (CNC) modified Bt composite (CNC@Bt) with enhanced efficiency for Cr(VI) removal. CNC@Bt exhibited an increased specific surface area and a porous structure, while maintaining the original crystal structure of Bt. This was achieved through a synergistic function of ion exchange, hydrogen bonding, electrostatic interactions, and steric hindrance. The adsorption of Cr(VI) by CNC@Bt followed the pseudo-second-order kinetic and Langmuir isotherm adsorption model. Moreover, the process was endothermic and spontaneous. At an initial Cr(VI) concentration of 20 mg/L and pH = 4.0, 10 g/L CNC@Bt achieved a removal rate of 92.7%, and the adsorption capacity was 1.85 mg/g, significantly higher than bare Bt (37.9% and 0.76 mg/g). The removal efficiency remained consistently above 80% over a wide pH range, indicating the potential practical applicability of CNC@Bt. With its fast adsorption rate, pH adaptability, and stable performance, CNC@Bt presents promising prospects for the rapid treatment of Cr-contaminated wastewater.

An Updated Overview of Magnetic Composites for Water Decontamination

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

Enhanced adsorption performance of oxytetracycline in aqueous solutions by Mg-Fe modified suaeda-based magnetic biochar

Oxytetracycline (OTC) in the waste water can be removed by biochar adsorption. How to separate the biochar adsorbed antibiotics from the wastewater was also a problem. The nontoxic magnetic biochar was prepared from Suaeda biochar (800SBC) by mafic bimetal modification, and used for the removal of OTC. The results of XRD and VSM indicated that the main composition of biochar was ferrite. Then through batch adsorption experiments, the adsorption kinetics, isothermal adsorption, thermodynamics, and coexisting ion and adsorbent regeneration experiments were studied. Through the fitting of the adsorption model, it was found that Mg-Fe@800SBC(1:1) and 800SBC belonged to chemisorption. 800SBC was consistent with the Langmuir model, mainly monolayer adsorption, and Mg-Fe@800SBC(1:1) was consistent with the Freundlich model, mainly multilayer adsorption. The adsorption processes of the two materials were spontaneous, endothermic and entropic decreasing processes. The maximum adsorption capacity of the Mg-Fe@800SBC(1:1) for OTC from the Sips L-F model was 82.83 mg/g. Through various characterizations of magnetic biochar, it was found that the adsorption mechanism of the modified biochar included the hydrogen bonds between the oxygen-containing functional group of biochar and the -NH2 group of OTC, π-π EDA interaction, electrostatic attraction and complexation. Coexistence anions (CO32- and PO43-) have a negative effect on the adsorption process.

Improvement of the specific surface area of biochar by calcium-precipitated nanoparticles synthesized by microbial induction as a template skeleton: Removal mechanism of tetracycline in water

The template method is an effective means to improve the specific surface area and porosity of biochar, but the synthesis of template agents and the way they are integrated with biomass materials still need further development. Therefore, the free Pseudomonas sp. Y1 was used to synthesize calcium-precipitated nanoparticles (CPN) on sludge as a fused template skeleton to enlarge the surface area of sludge biochar facilitating the adsorption of tetracycline (TC) in this work. The modified biochar (FBC) showed excellent specific surface area (448.55 m2 g-1) and porosity (0.0053 cm³ g-1), stable morphological structure, abundant active functional groups, and appreciable adsorption capacity (65.43 mg g-1) based on several characterization and adsorption experiments. Moreover, the adsorption model postulated that the removal of TC is mainly a chemisorption-based heat-trapping, disordered multilayer interaction. In detail, this process involved the joint contribution from electrostatic interactions, ligand exchange, hydrogen bonding, π-π bonding, complexation, and pore filling. Meanwhile, the adaptability and stability of FBC were examined by pH and coexisting substances. This template skeleton induced by microorganisms can provide new insight into the modification of biochar with the template method.

Adsorptive removal of oxytetracycline using MnO2-engineered pine-cone biochar: thermodynamic and kinetic investigation and process optimization

Indiscriminate use of oxytetracycline is linked to the development of antibiotic-resistant genes, posing a serious threat to human health and ecosystem balance. This article reports the adsorptive elimination of oxytetracycline (OTC) from aqueous solution using a newly developed MnO2-modified pine-cone biochar (MnO2/PCBC). The MnO2/PCBC was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, CHNS analyzer, inductively coupled plasma-optical emission spectroscopy, and Brunauer-Emmett-Teller N2 adsorption analyzer. Batch adsorption experiments, designed using the central composite design framework of response surface methodology, were conducted to investigate the influence of process variables on the adsorption of OTC onto MnO2/PCBC. The optimized conditions for achieving maximum removal (88.1%) were found to be at pH 8, MnO2/PCBC dose 0.44 g/L, initial OTC concentration 200 mg/L, and temperature 303 K. The adsorption process follows Langmuir (R2=0.95) and Freundlich (R2=0.95) isotherms and pseudo-second-order (R2=0.99) adsorption kinetics. The adsorption process was found to be endothermic (ΔH0 = 33.04 kJ/mol) and spontaneous in nature (ΔG0 from -1.33 kJ/mol at 283 K to -5.65 kJ/mol at 313 K). The synthesized MnO2/PCBC could be recycled and reused for OTC removal with a percentage removal of around 80% after fifth cycle. The results indicate an effective removal of oxytetracycline with only 0.44 g/L MnO2/PCBC with maximum adsorption capacity of 357.14 mg/g which demonstrates improved performance in comparison to many adsorbents reported in literature. This implies that MnO2/PCBC offers potential to be developed into a cost-effective technique for antibiotic removal from water.

Study of the Efficiency of a Polycation Using the Diafiltration Technique in the Removal of the Antibiotic Oxytetracycline Used in Aquaculture

The presence of antibiotics in aquatic systems in recent years has become a global environmental and public health concern due to the appearance of strains resistant to these antibiotics. Oxytetracycline (OXT) is a high-impact antibiotic used for both human and veterinary consumption, and it is the second most used antibiotic in aquaculture in Chile. Based on the above, this problem is addressed using a linear polymer whose structure is composed of aromatic rings and quaternary ammonium groups, which will help enhance the removal capacity of this antibiotic. To obtain the polycation, a radical polymerization synthesis was carried out using (4-vinylbenzyl)-trimethylammonium chloride as the monomer. The polycation was characterized via Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The removal studies were conducted under different experimental conditions such as pH levels (3.0, 5.0, 7.0, 8.0, and 11.0), ionic strength (0.0-0.50 mg L-1 of NaCl), polymer dose (0.25-25.5 mg), variation of the antibiotic concentration (1-100 mg L-1), and evaluation of the maximum retention capacity, as well as load and discharge studies. The antibiotic retention removal was higher than 80.0%. The antibiotic removal performance is greatly affected by the effect of pH, ionic strength, molar ratio, and/or OXT concentration, as these parameters directly affect the electrostatic interactions between the polymer and the antibiotics. The diafiltration technique was shown to be highly efficient for the removal of OXT, with maximum removal capacities of 1273, 966, and 778 mg OXT g-1 polycation. In conclusion, it can be said that coupling water-soluble polymers to the diafiltration technique is an excellent low-cost way to address the problem of antibiotics in aquatic systems.

Removal of oxytetracycline from wastewater by biochar modified with biosynthesized iron oxide nanoparticles and carbon nanotubes: Modification performance and adsorption mechanism

The pollution problem of oxytetracycline (OTC) from wastewater becomes more serious, so an efficient, economical, and green adsorption material is urgently explored. In this study, the multilayer porous biochar (OBC) was prepared by coupling carbon nanotubes with iron oxide nanoparticles synthesized by Aquabacterium sp. XL4 to modify corncobs under medium temperature (600 °C) conditions. The adsorption capacity of OBC could reach 72.59 mg g-1 after preparation and operation parameters were optimized. In addition, various adsorption models suggested that OTC removal resulted from the combined effect of chemisorption, multilayer interaction, and disordered diffusion. Meanwhile, the OBC was fully characterized and exhibited a large specific surface area (237.51 m2 g-1), abundant functional groups, stable crystal structure, high graphitization, and mild magnetic properties (0.8 emu g-1). The OTC removal mechanisms mainly included electrostatic interactions, ligand exchange, π-π bonding reactions, hydrogen bonds, and complexation. pH and coexistence substance experiments revealed that the OBC possesses a wide pH adaptation range and excellent anti-interference ability. Finally, the safety and reusability of OBC were confirmed by repeated experiments. In summary, OBC as a biosynthetic material shows considerable potential for application in the field of purifying new pollution from wastewater.

The role of anthocyanin and kaolinite in modifying cabbage leaves biochar for removal of potentially toxic elements and pharmaceutical from aqueous solution

We investigated the feasibility of two novel engineered biochar composites by pyrolyzing cabbage leaves at 350 °C after pre-treating them with anthocyanin, followed by a post-treatment with kaolinite for the removal of two potentially toxic elements (copper and lead) and a pharmaceutical compound, metoprolol. Results showed that the Kaolinite-biochar composite (KB) exhibited the highest adsorption capacity, 188.67 and 48.07 mg/g for Pb and Cu at pH 5, and the anthocyanin-biochar composite (AB) exhibited the highest adsorption capacity: 41.15 mg/g for metoprolol at pH 6, compared to raw biochar respectively. The enhancement of the adsorption of heavy metal and metoprolol by KB and AB was due to an increase in certain oxygen functional groups, as confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results. The pseudo-second order kinetic model, along with Langmuir isotherm model, best described the kinetic and the isotherms for Pb, Cu and metoprolol in KB and AB composites, respectively. FTIR, XPS, and zeta potential measurements indicated that the sorption mechanisms involved electrostatic interaction, ion exchange, and complexation for the metals, while electrostatic interaction, H-bonding, π-πinteraction, and hydrophobic bonding were postulated as the contributing mechanisms in the sorption process of metoprolol. Anthocyanin and kaolinite could potentially be considered as alternative sustainable materials for modifying raw biochar and remediating toxic elements and pharmaceuticals in aqueous media.

Characterization and Co-Adsorption Mechanism of Magnetic Clay-Biochar Composite for De-Risking Cd(II) and Methyl Orange Contaminated Water

The application of the adsorption method in sewage treatment has recently become a hot spot. A novel magnetic clay-biochar composite (BNT-MBC) was fabricated by co-pyrolysis of bentonite and biomass after being impregnated with Fe (NO3)3·9H2O. Its adsorption capacity for Cd(II) and methyl orange was approximately doubled, reaching a maximum of 26.22 and 63.34 mg/g, and could be easily separated from the solution by using external magnets with its saturation magnetization of 9.71 emu/g. A series of characterizations including surface morphology and pore structure, elemental analysis, functional group analysis and graphitization were carried out, showing that the specific surface area was increased 50 times by loading 20 wt.% bentonite, while its graphitization and oxygen-containing functional groups were also enhanced. The isotherm fitting indicated that Cd(II) was adsorbed in multiple layers, while methyl orange was in both monolayer and multilayer adsorptions. The kinetic fitting indicated that chemisorption was the rate-limiting step of both, and it was also a complex process controlled by two steps with the fitting of intra-particle diffusion. In the binary system of Cd(II) and methyl orange, the co-existing pollutants facilitated the adsorption of the original one, and there was no competition between adsorption sites of Cd(II) and methyl orange. BNT-MBC also exhibited good reusability and can be magnetically recovered for recycling. Thus, the magnetic clay-biochar composite BNT-MBC is a cost-effective and promising adsorbent for simultaneous removing Cd(II) and methyl orange from wastewater.

Carbon nanotube-loaded copper-nickel ferrite activated persulfate system for adsorption and degradation of oxytetracycline hydrochloride

In this study, a new composite (MWCNTs-CuNiFe₂O₄) prepared by loading magnetic CuNiFe₂O₄ particles onto carboxylated carbon nanotubes (MWCNTs) through co-precipitation was applied to remove oxytetracycline hydrochloride (OTC-HCl) in solution. The magnetic properties of this composite could address of the issue of difficulty associated with the separation of MWCNTs from mixtures when applied as an adsorbent. In addition to the good adsorption properties recorded for MWCNTs-CuNiFe₂O₄ towards OTC-HCl, this developed composite could be used to activate potassium persulfate (KPS) for an efficient degradation of OTC-HCl. The MWCNTs-CuNiFe₂O₄ was systematically characterized using Vibrating Sample Magnetometer (VSM), Electron Paramagnetic Resonance (EPR) and X-ray Photoelectron Spectroscopy (XPS). The influence of dose of MWCNTs-CuNiFe₂O₄, the initial pH, the amount of KPS and the reaction temperature on the adsorption and degradation of OTC-HCl by MWCNTs-CuNiFe₂O₄ were discussed. The adsorption and degradation experiments showed that MWCNTs-CuNiFe₂O₄ exhibited an adsorption capacity of 270 mg·g^-1 for OTC-HCl with the removal efficiency 88.6% at 303 K (at an initial pH 3.52, 5 mg KPS, 10 mg composite, 10 mL reaction concentration 300 mg·L^-1 of OTC-HCl). The Langmuir and Koble-Corrigan models were used to describe the equilibrium process while the Elovich equation and Double constant model were suitable to describe the kinetic process. The adsorption process was based on single-molecule layer reaction and non-homogeneous diffusion process. The mechanisms of adsorption were complexation and hydrogen bond whereas active species such as SO₄^‧-, ^‧OH and ¹O₂ were confirmed to have played a major role in the degradation of OTC-HCl. The composite was also found to be very stable with good reusability property. These results confirm the good potential associated with the use of MWCNTs-CuNiFe₂O₄/KPS system for the removal of some typical pollutants from wastewater.

Mechanistic insight into adsorptive removal of ionic NOR and nonionic DEP organic contaminates by clay-biochar composites

The synthesis of clay-biochar composite has been recognized as an effective way to enhance the removal of pollutants. The interaction between clay mineral and biomass during thermal pyrolysis and the sorption capacity for ionic/nonionic organic containments have not been elaborated. In this study, two types of biochar were obtained from pyrolytic carbonization of the cellulosic-rich corn straw (C) and lignin-rich pine wood (P) at 500 or 700 °C. Typical clay minerals kaolinite and montmorillonite were selected to prepare clay-biochar composite. The results showed that the addition of clay mineral could strengthen dehydration reaction of corn straw biomass and reinforce its carbon structure. Montmorillonite-biochar composite owned more CC functional groups and porous structure than kaolinite-biochar composite. The addition of clay minerals could promote electrostatic attraction of ionic formed norfloxacin (NOR) on clay-pine wood biochar. However, the sorption capacity of nonionic diethyl phthalate (DEP) adsorption on clay-corn straw biochar decreased, owing to that clay increased the compactness of the biochar carbon structure, thus inhabited hydrophobic partition of nonionic organic compounds on disordered carbon fraction. The results from this study provide insights into the suitable contaminated site remediation by clay-biochar composite.

Enhanced removal of oxytetracycline from wastewater using bimetallic Fe/Ni nanoparticles combined with ZIF-8 nanocomposites

The integration of metal-organic frameworks with other functional materials has recently emerged as a promising approach for creating innovative materials for environmental remediation. Here, a nano-sized iron/nickel (Fe/Ni) functionalized zeolitic imidazolate framework-8 (ZIF-8-Fe/Ni) was fabricated for oxytetracycline (OTC) removal from wastewater. Cyclic voltammetry and amperometric I-t measurements indicated that OTC was degraded by ZIF-8-Fe/Ni. X-ray diffraction spectroscopy (XRD), transmission electron microscopy mapping (TEM-mapping) and X-ray photoelectron spectroscopy (XPS) indicated that Fe/Ni was evenly dispersed throughout ZIF-8 and partially oxidized after reaction with OTC. OTC adsorption isotherms and kinetics best fitted the Langmuir isotherm (R² > 0.982) and pseudo-second-order model (R² > 0.997), respectively. Reduction kinetics data followed the pseudo-first-order model (R² > 0.905), where the apparent activation energy (Ea) was 22.9 kJ mol^-1, demonstrating that OTC degradation was mainly via a chemical process. The practical removal efficiency of OTC from real wastewater by ZIF-8-Fe/Ni was 92.6%, where even after application of ZIF-8-Fe/Ni for 5 consecutive removal cycles, a high OTC removal of 74.9% was maintained. Thus ZIF-8-Fe/Ni exhibited both high removal efficiency and good recyclability.

Co-adsorption capabilities and mechanisms of bentonite enhanced sludge biochar for de-risking norfloxacin and Cu2+ contaminated water

Various bentonite-sludge biochar composites were fabricated by a sequence of loading and pyrolysis for the simultaneous removal of norfloxacin (NOR) and copper (Cu²⁺) from an aqueous solution. The morphology and characteristics of obtained composites were reflected through cation exchange capacity (CEC), BET specific surface area (S_BET), SEM, XRD, FTIR and XPS. The isothermal adsorption results showed that Sips adsorption model fitted better for the adsorption of NOR and Cu²⁺ during co-adsorption. The theoretical maximum adsorption capacity of BT:2 SB (the mass ratio of bentonite to sludge is 1:2) for NOR and Cu²⁺ was 89.36 mg g^-1 and 104.10 mg g^-1 at 25 °C in the co-adsorption system. The thermodynamic results showed the capture of NOR and Cu²⁺ was spontaneous, accompanied by an endothermic reaction with different randomness. In the co-adsorption system, the two were antagonistic to each other due to competition for the adsorption sites of hydroxyl, carboxylic acid and negatively charged provided by bentonite-sludge biochar. This study suggests that using natural mineral as a pyrolysis improver for sludge biochar can product the value-enhanced biochar for simultaneous removal of antibiotic and metal contaminants.

Performance and mechanism of sycamore flock based biochar in removing oxytetracycline hydrochloride

In this study, sycamore flocs (SF), which caused environmental and health problems, were utilized to prepare biochar. SFB_2-900 obtained under the conditions of activation agent K₂CO₃, pyrolysis temperature 900℃ and m(K₂CO₃):m(BC) 2 had the strongest adsorption capacity (730 mg/g) for oxytetracycline hydrochloride (OTC-HCl). The pseudo-second-order kinetic model and Langmuir model described the adsorption kinetics and isotherms best. SFB_2-900 exhibited high OTC-HCl adsorption capacity in both higher ionic strength and wide pH range. The theoretical simulation indicated that the closest interaction distance between OTC-HCl and SFB_2-900 was 2.44 Å via π-π stacking configuration. Pore filling, π-π electron donor acceptor (EDA) interaction, H-bonding and electrostatic interactions were also involved in the process of OTC-HCl removal. SFB_2-900 showed great removal efficiency for OTC-HCl in different water matrices and good regeneration ability. This study solved the problems caused by SF, realized waste biomass recycling, and achieved preparing high-efficient adsorbent for antibiotic.

Advances in decontamination of wastewater using biomass-basedcomposites: A critical review

Contaminant removal from wastewater using natural biosorbents has been widely studied as a suitable and environmentally benign alternative for conventional techniques. Currently, researchers are working on various biomass-based composites for wastewater remediation to improve the performance of natural biosorbents. This review takes into focus a wide range of biomass-based composites like hydrogel composites, metal oxide composites, magnetic composites, polymer composites, carbon nanotubes (CNTs) and graphene composites, metal organic framework composites (MOFs) and clay composites for the removal of various contaminants from wastewater. It is evident from the literature survey that the composite fabrication involves the modification of morphological and textural features of the biomass which results in significant enhancement of adsorption capacity. Apart from this, regeneration of the used biomass-based composite is also studied in depth in order to overcome the problem of solid waste generation. This review would prove to be beneficial for researchers who are currently focusing on the development of cost-effective, easily available, recyclable biomass-based composites with enhanced adsorption capacities for wastewater treatment.

Functionalizing non-smectic clay via methoxy-modification for enhanced removal and recovery of oxytetracycline from aqueous media

Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir's models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g^-1. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C-N bonds in the N1s peaks by forming tertiary amide C-N and methoxy O-CH₃ bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.

Facile Fabrication of Flocculent Magnesium Silicate for the Adsorption of Oxytetracycline

The discharge of antibiotics and the potential threat to organisms posed by this have received increasing attention. In this work, flocculent magnesium silicate (FMS) was fabricated by a facile hydrothermal and freeze-drying process, and its adsorption behavior for antibiotic oxytetracycline (OTC) was investigated. FMS presented a sepiolite-type structure and the alkaline solution promoted its hydroxylation. A hierarchical pore structure ranging from micropores to macropores and a high specific surface area of 660 m2/g were exhibited. FMS exhibited a higher adsorption amount in neutral solution than in acidic or alkaline conditions as the physicochemical properties of FMS and OTC were significantly affected by the pH. Adsorption isotherm could be well-described by the Langmuir model, and the calculated saturated adsorption capacity was as high as 265 mg/g. Adsorption kinetics followed the pseudo-second-order kinetic model, and the adsorption rate-controlling step was intraparticle diffusion. Thermodynamic parameters indicated that the adsorption was a spontaneous physicochemical reaction. After five cycles, around 91% of the adsorption performance was still maintained, demonstrating the excellent reusability of FMS. The sepiolite-type FMS fabricated in this work could be applied to remove OTC from wastewater.