Adsorption behavior of doxycycline antibiotic on NaY zeolite from wheat ( Triticum aestivum ) straws ash

Lignocellulosic biomass for biochar production: A green initiative on biowaste conversion for pharmaceutical and other emerging pollutant removal

Lignocellulosic waste generation and their improper disposal has accelerated the problems associated with increased greenhouse gas emissions and associated environmental pollution. Constructive ways to manage and mitigate the pollution associated with lignocellulosic waste has propelled the research on biochar production using lignocellulose-based substrates. The sustainability of various biochar production technologies in employing lignocellulosic biomass as feedstock for biochar production not only aids in the lignocellulosic biomass valorization but also helps in carbon neutralization and carbon utilization. Functionalization of biochar through various physicochemical methods helps in improving their functional properties majorly by reducing the size of the biochar particles to nanoscale and modifying their surface properties. The usage of engineered biochar as nano adsorbents for environmental applications like dye absorption, removal of organic pollutants and endocrine disrupting compounds from wastewater has been the thrust areas of research in the past few decades. This review presents a comprehensive outlook on the up-to-date research findings related to the production and engineering of biochar from lignocellulosic biomass and their applications in environmental remediation especially with respect to wastewater treatment. Further a detailed discussion on various biochar activation methods and the future scope of biochar research is presented in this review work.

Magnetic NH2-MIL-101(Al)/Chitosan nanocomposite as a novel adsorbent for the removal of azithromycin: modeling and process optimization

In the present study, the magnetic NH₂-MIL-101(Al)/chitosan nanocomposite (MIL/Cs@Fe₃O₄ NCs) was synthesized and used in the removal of azithromycin (AZT) from an aqueous solution for the first time. The as-synthesized MIL/Cs@Fe₃O₄ NCs was characterized by SEM, TEM, XRD, FTIR, BET, and VSM techniques. The effect of various key factors in the AZT adsorption process was modeled and optimized using response surface methodology based on central composite design (RSM-CCD). The low value of p-value (1.3101e-06) and RSD (1.873) parameters, along with the coefficient of determination > 0.997 implied that the developed model was well fitted with experimental data. Under the optimized conditions, including pH: 7.992, adsorbent dose: 0.279 g/L, time: 64.256 min and AZT concentration: 10.107 mg/L, removal efficiency and AZT adsorption capacity were obtained as 98.362 ± 3.24% and 238.553 mg/g, respectively. The fitting of data with the Langmuir isotherm (R²: 0.998, X²: 0.011) and Pseudo-second-order kinetics (R²: 0.999, X²: 0.013) showed that the adsorption process is monolayer and chemical in nature. ΔH° > 0, ΔS° > 0, and ∆G° < 0 indicated that AZT removal was spontaneous and endothermic in nature. The effect of Magnesium on AZT adsorption was more complicated than other background ions. Reuse of the adsorbent in 10 consecutive experiments showed that removal efficiency was reduced by about 30.24%. The performance of MIL/Cs@Fe₃O₄ NCs under real conditions was also tested and promising results were achieved, except in the treatment of AZT from raw wastewater.

Reducing the negative impact of ceftriaxone and doxycycline in aqueous solutions using ferrihydrite/plant-based composites: mechanism pathway

The adsorption of ceftriaxone (CET) and doxycycline (DOX) from aqueous solution using ferrihydrite/plant-based composites (silica rice husk) to reduce their negative impact on the ecosystem was adequately studied. On the other hand, phosphate and humic acid are often found in water and soil; in view of this, their effects on the adsorption of CET and DOX were investigated. The results showed that the removal of ceftriaxone decreased with an increase in pH, while that of doxycycline did not. Ferrihydrite with 10% silica rice husk (Fh-10%SRH) has the highest maximum adsorption capacity of 139 and 178 mg g^-1 for CET and DOX, respectively, at room temperature based on Liu's adsorption isotherm. This implies that the presence of silica rice husk increases CET and DOX uptake due to an increase in the pore volume of FH-10%SRH. The results showed that phosphate had a significant inhibition role on CET adsorption and minor on DOX, whereas humic acid salt affected neither case. Increase in temperature up to 333 K favored the adsorption of both contaminants. The proposed adsorption mechanisms of ceftriaxone are electrostatic interaction, n-π interaction, and hydrogen bond, while that of DOX entails n-π interaction and hydrogen bond.

Antibiotic adsorption by natural and modified clay minerals as designer adsorbents for wastewater treatment: A comprehensive review

Increased antibiotic use worldwide has become a major concern because of their health and environmental impacts. Since most antibiotic residues can hardly be removed from wastewater using conventional treatments, alternative methods receive great attention. Adsorption is one of the most efficient and cost-effective treatment methods for antibiotics. Among the adsorbents, clay minerals have garnered increasing attention due to their unique properties including availability, high specific surface area, low cost, cation exchange capacity, and good removal efficiency. This paper reviews the recent progress made in the use of natural and modified clay minerals for the removal of antibiotics from water. First, the sources, occurrence, removal and health effects of the antibiotics commonly encountered in water bodies are described. Antibiotic concentration levels and average removal efficiencies measured in conventional activated sludge treatment systems worldwide are also provided to better address the problem. Second, the review explores the characteristics of clay minerals as adsorbent of antibiotics and the factors affecting the adsorption. The review identifies and discusses the future trends and strategies used to increase the adsorption capacity of clay minerals by modification and combination techniques (intercalation of novel functional groups such as organocations, biopolymers and metal pillared-clay minerals, combination with biochar or thermal activation). The quantitative comparisons of clay minerals' ability for antibiotic removal are given. Some natural clay minerals have good removal potential for antibiotics, with maximum adsorption capacities over 100 mg/g. For most other adsorbents, surface modifications and combination techniques resulted in improved adsorption properties (including higher surface area, enhanced adsorption capacity, increased stability and mechanical strength). Finally, the application of these adsorbents at pilot scale, using real wastewater samples, their reuse, economic analysis and life cycle assessment are other issues that have been considered.

Salt sealing induced in situ N-doped porous carbon derived from wheat bran for the removal of doxycycline from aqueous solution

In situ N-doped porous carbon (NPC) derived from wheat bran via a convenient salt sealing and air-assisted strategy was prepared for the removal of doxycycline (DOX) from aqueous solution. The NPC was precisely characterized by SEM, FTIR, XPS and BET analysis. Additionally, the experimental variables including contact time, adsorbent dosage of NPC and pH were optimized by using Box-Behnken design (BBD) under response surface methodology (RSM). The predicted adsorption capacity of DOX was found to be 291.14 mg g-1 under optimalizing experimental conditions of 196 min contact time, 0.2 g L-1 adsorbent dosage and pH 5.78. The adsorption experimental data fitted Langmuir, Koble-Corrigan and Redlich-Peterson models well, and the pseudo-second-order model perfectly described the DOX adsorption process onto NPC. Thermodynamic parameters of DOX adsorbed onto NPC indicated that the adsorption process was spontaneous and endothermic. Moreover, the adsorption of DOX on NPC was mostly controlled by electrostatic interaction, π-π electron-donator-acceptor (EDA) interaction, hydrogen-bonding and Lewis acid-base effect. Besides, the N element of NPC also played a role in capturing DOX. The maximum monolayer adsorption capacity of DOX was turn out to be 333.23 mg g-1 at 298 K, which suggested that the NPC could be a prospectively adsorbent for the removal of DOX from wastewater.

Co-Cu oxide nano-flake adsorbent for tetracycline removal from aqueous solution

In this study, a new adsorbent based on Co-Cu oxide nano-flakes was investigated to remove tetracycline from aqueous systems. Ultrasonic-assisted co-precipitation method has been used to synthesize the adsorbent nanoparticles with different precursor concentration of Cu2+/Co2+. The properties of the adsorbents have been investigated using BET, FESEM/EDS, XRD, and FTIR techniques. The removal experiment results show that the maximum tetracycline adsorption (qmax=195mg·gr-1) was obtained for the adsorbent synthesized by Cu2+:Co2+ molar ratio of 1:5. The adsorbent nanoparticles have a Co3O4 spinel crystal structure and a flake-shape morphology with thickness of 20 nm. Incorporation of copper atoms in the spinel structure was confirmed by XRD and FTIR results and hence, effectively promotes the removal of the tetracycline. The effect of various parameters such as adsorbent weight, pH, and time on the kinetics of adsorption was investigated. The results showed that the Langmuir isotherm was in better agreement with the experimental data of tetracycline adsorption. The overall rate of adsorption follows the first-order kinetic model, although the results of intraparticle diffusion model showed that diffusion mechanism is one of the controlling steps during the adsorption process.

Effective removal of doxycycline from aqueous solution using CuO nanoparticles decorated poly(2-acrylamido-2-methyl-1-propanesulfonic acid)/chitosan

The primary focus of the present study was to synthesize CuO nanoparticles decorated poly(2-acrylamido-2-methyl-1-propanesulfonic acid)/chitosan to explore its potential for uptake of doxycycline (DXN) from water. The composite material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction and thermogravimetric analysis-differential thermal analysis. Central composite design under response surface methodology was opted to optimize the process variables (pH, adsorbent dosage, contact time and initial concentration of DXN) for obtaining the highest removal efficiency. The removal of DXN reached 98.84% at 303 K under the optimum conditions of pH 7.0, equilibrating time of 70 min, adsorbent dose of 20 mg/25 mL and initial concentration of 50 mg L-1. The Langmuir isotherm and pseudo-second-order kinetic models fitted best with the experimental data. The values of ΔG° (- 29.159 to - 31.997 kJ mol-1), ΔH° (56.768 kJ mol-1) and ΔS° (283.382 J mol-1 K-1) demonstrated the spontaneous and endothermic nature of adsorption process. The adsorption/desorption study revealed the reusability of the prepared composite material for DXN uptake up to six cycles.

Silica-clay nanocomposites for the removal of antibiotics in the water usage cycle

The increasingly frequent detection of resistant organic micropollutants in waters calls for better treatment of these molecules that are recognized to be dangerous for human health and the environment. As an alternative to conventional adsorbent material such as activated carbon, silica-clay nanocomposites were synthesized for the removal of pharmaceuticals in contaminated water. Their efficiency with respect to carbamazepine, ciprofloxacin, danofloxacin, doxycycline, and sulfamethoxazole was assessed in model water and real groundwater spiked with the five contaminants. Results showed that the efficacy of contaminant removal depends on the chemical properties of the micropollutants. Among the adsorbents tested, the nanocomposite made of 95% clay and 5% SiO₂ NPs was the most efficient and was easily recovered from solution after treatment compared with pure clay, for example. The composite is thus a good candidate in terms of operating costs and environmental sustainability for the removal of organic contaminants.

Removal of Antibiotics from Aqueous Solutions by a Carbon Adsorbent Derived from Protein-Waste-Doped Biomass

Antibiotic pollution in water is an urgent environmental problem. A novel carbon adsorbent derived from powdery puffed waterfowl feather (PPWF)-doped Phragmites australis (PA) was proposed for enhancing the removal of antibiotics from water in this study. Amoxicillin (AMX) and cephalexin (CEX) were selected as typical antibiotics. PPWF-doped (FPAC) and -undoped (PAC) carbon adsorbents were developed to test the adsorption capacities and mechanisms of AMX and CEX. Characterization techniques such as N₂ adsorption/desorption, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, elemental analysis, and Boehm titration were used to determine the properties of adsorbents. Results showed that more microporous structure and surface functional groups are exhibited in FPAC compared to PAC. The nitrogen-containing functional groups were introduced in FPAC. Adsorption capacities at different contact times, pH, and initial concentration were investigated by batch experiments. The AMX and CEX maximum adsorption capacities of FPAC are 25.2 and 30.1% higher than those of PAC, respectively. The kinetic data were well represented by the pseudo-second-order model for AMX and CEX adsorption. The equilibrium data agreed well with the Langmuir model for AMX adsorption and the Freundlich model for CEX adsorption. The adsorption mechanism of AMX and CEX was chemisorption, such as electrostatic attraction and covalent bonding.

Comparative adsorption mechanism of doxycycline and Congo red using synthesized kaolinite supported CoFe2O4 nanoparticles

Kaolinite supported CoFe₂O₄ (KCF) was synthesized and employed to adsorb doxycycline (DOX), an antibiotic and Congo red (CR), a dye from aqueous solution. The prepared KCF nanocomposite was treated in a muffle furnace at 300, 500 and 700 °C, and thereafter characterized. X-ray diffractogram revealed structural damage of kaolinite and appearance of distinct peaks of CoFe₂O₄ with an increase in calcination temperature, while transmission electron microscopy (TEM) images showed that CoFe₂O₄ nanoparticles were supported on the lamellar surface of kaolinites. Comparative adsorption mechanism of the two targeted contaminants showed that adsorption of DOX was influenced by hydrogen bond and n-π interaction, while that of CR was due to hydrophobic interaction and hydrogen bond. However, the adsorption of the two contaminants was best fitted to the isotherm that was proposed by Langmuir, with a monolayer maximum adsorption capacity of 400 mg g^-1 at 333 K for DOX, and 547 mg g^-1 at 298 K for CR. The removal of DOX from aqueous solution was favored by an increase in temperature (endothermic), while that of CR was exothermic. Thermodynamics studies confirmed that the adsorption of the two contaminants is feasible and spontaneous. The presence of natural organic matter (NOM) did not affect the removal of the two contaminants. Regeneration and reusability study showed that KCF is economically viable. Therefore, introducing inorganic particles like cobalt ferrite into the matrix of kaolinites provides a composite with promising adsorption capacity.

Effect of Cu(II) on adsorption of tetracycline by natural zeolite: performance and mechanism

The purpose of this study was to investigate the effect of Cu(II) on the adsorption performance and mechanism of tetracycline (TC) adsorption by natural zeolite (NZ) in aqueous solution. Low levels of Cu(II) (<0.01 mmol/L) enhanced the extent of TC adsorption from ∼0.4 mg/g (in the absence of Cu(II)) to ∼0.5 mg/g (with 0.01 mmol/L Cu(II)), resulting in 99% removal of the total TC content. The TC adsorption gradually decreased with increase in the initial pH, but the coexistence of Cu(II) lowered the extent of decrease. The adsorption process was better simulated by the pseudo-second-order kinetics model, but the isotherm model that was more fitting changed from the Langmuir to the Freundlich model as Cu(II) increased, indicating the coexistence of Cu(II) and TC altered the adsorption mechanisms. However, the residual TC in solution increased from 0 to ∼6 mg/L as the concentration of Cu(II) increased from 0 to 1 mmol/L, suggesting a competition between TC and Cu(II) for the adsorption sites in NZ. Fourier transform infrared spectroscopy analysis showed that the functional groups on the surface of NZ changed after the adsorption of TC, suggesting that complex reactions had occurred on the surface of the adsorbent.

An investigation on the capability of magnetically separable Fe3O4/mordenite zeolite for refinery oily wastewater purification

Damage to the water resources and environment as a consequence of oil production and use of fossil fuels, has increased the need for applying various technologies and developing effective materials to remove contaminates from oily wastewaters resources. One of the challenges for an economic industrial wastewater treatment is separation and reusability of the developed purifying agents. Development of magnetic materials could potentially facilitate easier and more economic separation of purifying agents. Therefore, herein we have synthesised an efficient and easily recyclable Fe₃O₄/mordenite zeolite using a hydrothermal process to investigate its purification capability for wastewater from Kermanshah oil refinery. The synthesised Fe₃O₄/mordenite zeolite was characterised using XRD, FTIR, SEM, EDX, XRF and BET analysis. XRD result showed that the synthesised Fe₃O₄/mordenite zeolite comprised sodium aluminium silicate hydrate phase [01-072-7919, Na₈(Al₆Si₃₀O₇₂)(H₂O)_9.04] and cubic iron oxide phase [04-013-9808, Fe₃O₄]. Response Surface Method (RSM) combined with Central Composite Design (CCD) was used to identify the optimum operation parameters of the pollutant removal process. The effect of pH, contact time and Fe₃O₄/mordenite zeolite amount on the Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and Nephelometric Turbidity Unit (NTU) were investigated. It was found that pH was the most significant factor influencing COD and BOD removal but the quantity of Fe₃O₄/mordenite zeolite was the most influential factor on the turbidity removal capacity. The optimum removal process conditions were identified to be pH of 7.81, contact time of 15.8 min and Fe₃O₄/mordenite zeolite amount of 0.52% w/w. The results show that the regenerated Fe₃O₄/mordenite zeolite can be reused for five consecutive cycles in purification of petroleum wastes.

Lignin xanthate resin-bentonite clay composite as a highly effective and low-cost adsorbent for the removal of doxycycline hydrochloride antibiotic and mercury ions in water

Natural-occurring polymer intercalated inorganic clay composites have received increasing interests in water cleanup for the features of eco-friendliness, cost-effectiveness, and availability. Herein, a new lignin xanthate resin (LXR) intercalated bentonite clay composite (LXR-BT) for the adsorption of representative organic doxycycline hydrochloride (DCH) antibiotic and inorganic Hg(II) in water was created through a feasible process. Structural characterizations by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Thermo gravimetric analysis (TG), and scanning electron microscopy (SEM) confirmed LXR was successfully intercalated between the layers of bentonite clay. The adsorption performance of DCH/Hg(II) by LXR-BT was studied in detail with varied dosage, solution pH, contact time, and initial DCH/Hg(II) concentration. The results indicated that the adsorption capacities of DCH/Hg(II) on LXR-BT were much higher than that on bentonite, and the adsorption kinetics and isotherms followed the pseudo-second-order model and Langmuir model, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the adsorption mechanisms of DCH (or Hg(II)) was mainly due to π-π interaction and hydrogen bonding interaction of DCH (or the complexation of Hg(II)) with the functional groups in the LXR-BT. This study suggested the possibility of LXR-BT as a new cost-effective adsorbent for both organic and inorganic pollutants removal in water.

Chemically stable polyarylether-based covalent organic frameworks

The development of crystalline porous materials with high chemical stability is of paramount importance for their practical application. Here, we report the synthesis of polyarylether-based covalent organic frameworks (PAE-COFs) with high crystallinity, porosity and chemical stability, including towards water, owing to the inert nature of their polyarylether-based building blocks. The PAE-COFs are synthesized through nucleophilic aromatic substitution reactions between ortho-difluoro benzene and catechol building units, which form ether linkages. The resulting materials are shown to be stable against harsh chemical environments including boiling water, strong acids and bases, and oxidation and reduction conditions. Their stability surpasses the performance of other known crystalline porous materials such as zeolites, metal-organic frameworks and covalent organic frameworks. We also demonstrate the post-synthetic functionalization of these materials with carboxyl or amino functional groups. The functionalized PAE-COFs combine porosity, high stability and recyclability. A preliminary application of these materials is demonstrated with the removal of antibiotics from water over a wide pH range.