Batch and column study on tetracycline removal using green synthesized NiFe nanoparticles immobilized alginate beads

Adsorptive removal of norfloxacin from aqueous solutions by Fe/Cu CNS-embedded alginate-carboxymethyl cellulose-chitosan beads

The pervasive application of pharmaceuticals in aquatic environments has acquired much focus owing to their nonbiodegradability and eco-toxicity, which might readily destroy the ecological balance. Developed chitosan-coated Fe-Cu CNS alginate-CMC beads (NBs) were utilized in this study to adsorb the quinolone antibiotic norfloxacin (NOR) from water for the first time. Under ideal conditions (CNOR: 20 mg L-1; sorbent conc.: 2000 mg L-1; sorbent dosage: 0.15 g; interaction time: 300 min; solution pH: 6.0), about 86% NOR removal was achieved through batch mode. The removal performance for NOR was examined concerning pH, ionic strength, and coexisting micropollutants. The greatest NOR removal was attained on NBs with the greatest Langmuir adsorption capacity of 355 mg g-1 due to numerous mechanisms such as sorbent pore filling, electrostatic attraction, π-π attraction and hydrogen bonding. Studies using environmentally significant algae, such as Scenedesmus sp., to analyze the residual toxicity of treated NOR solution revealed a significant reduction in their toxic effects. Current research has demonstrated that nanocomposite beads are an excellent wastewater treatment material with promising industrial applications due to their ease of synthesis, exceptional surface adsorption properties, stability, and environmentally friendly reaction.

Sodium carbonate/biochar-supported sodium alginate-modified nano zero-valent iron for complete adsorption and degradation of tetracycline in aqueous solution

The aggregation of nanoscale zero-valent iron (NZVI) is one of the biggest challenges for its application when treating contaminants in aquatic environment. We report a study on synthesis of sodium carbonate-modified biochar (BC-600) combined with sodium alginate (SA)-modified NZVI (SA/NZVI@BC-600) for the removal of tetracycline (TC). When the initial concentration of TC was 20 mg/L, 100% TC was removed by SA/NZVI@BC-600 at an initial pH of 7 under room temperature of 25 °C within 90 min. In addition, the reactivity of the SA/NZVI@BC-600 composites toward TC removal was not obviously declined after 4 cycles. SA/NZVI@BC-600 shows high reactivity, stability, and reusability. This excellent performance of SA/NZVI@BC-600 was related to the addition of SA and BC-600. The best performance of the SA/NZVI@BC-600 system was observed under weakly acidic and neutral conditions. Increasing the initial concentration and lowering the reaction temperature had a slight negative effect on the removal of TC by SA/NZVI@BC-600. In addition, the presence of CO32- and HCO3- had a significant negative effect on the degradation of TC. Meanwhile, ·OH and ·O2- played the leading role in TC degradation. This study not only reported a novel strategy of synthesizing an excellent BC modified NZVI based catalyst but also evaluated its promising application for antibiotic degradation in aqueous solution.

Doped graphitic carbon nitride (g-C3N4) catalysts for efficient photodegradation of tetracycline antibiotics in aquatic environments

Tetracyclines (TCs) antibiotics are very common and often used in both human and veterinary medicines. More than 75% of TCs are excreted in an active condition and released into the environment, posing a risk to the ecosystem and human health. Residual antibiotics are in global water bodies, causing antibiotic resistance and genotoxicity in humans and aquatic organisms. The ever-increasing number of multi-resistant bacteria caused by the widespread use of antibiotics in the environment has sparked a renewed interest in developing more sustainable antibiotic degradation processes. In this regard, photodegradation technique provides a promising solution to resolve this growing issue, paving the way for complete antibiotic degradation with the generation of non-toxic by-products. As a fascinating activity towards visible light range shown by semiconductor, graphitic carbon nitride (g-C₃N₄) has a medium bandgap, non-toxicity, chemically stable complex, and thermally great strength. Recent studies have concentrated on the performance of g-C₃N₄ as a photocatalyst for treating wastewater. Pure g-C₃N₄ exhibits limited photocatalytic activity due to insufficient sunlight usage, small surface area, and a high rate of recombination of electron and hole ([Formula: see text] & [Formula: see text]) pairs created in photocatalytic activity. Doping of g-C₃N₄ is a very effective method for improving the activity as element doped g-C₃N₄ shows excellent bandgap and electronic structure. Doping significantly broadens the light-responsive range and reduces recombination of e^- & h⁺ pairs. Under above context, this review provides a systematic and comprehensive outlook of designing doped g-C₃N₄ as well as efficiency for TCs degradation in aquatic environment.

Novel biologically synthesized metal nanopowder from wastewater for dye removal application

A novel adsorbent based on metal sulfide nanoparticles (MeSNPs) was biologically synthesized from metallic wastewater and examined for azo dyes removal from aqueous solution in batch and continuous systems. The size of the MeSNPs was in the range of 8-10 nm, with an average specific surface area of 120.4 m²/g. Batch adsorption study was then carried out using Direct Red 80 (DR 80) and Mordant Blue 9 (MB 9) as the model azo dyes by varying MeSNPs dosage, contact time, pH, and initial dye concentration. More than 99% removal efficiency of both the dyes was achieved by using MeSNPs at the following optimum conditions: 200 mg dosage, pH 2, 6 min contact time, and 100 mg L^-1 initial dye concentration. The batch sorption isotherm results were described using the Sips model, with the maximum predicted capacity values of 143.7 and 198.3 mg of dye per gram of adsorbent for DR 80 and MB 9, respectively. Besides, the sorption kinetic data for both the dyes followed the pseudo-second-order rate. Furthermore, maximum desorption efficiency values of 93% for DR 80 and 97% for MB 9 were achieved using an aqueous solution of pH 12, thus indicating that the adsorbent can be regenerated and reused further. Dynamic adsorption of the dyes was studied using a fixed-bed column with the MeSNPs as a function of liquid flow rates. The results showed an increase in breakthrough time with a decline in the flow rates for both DR 80 and MB 9 and the breakthrough behavior was explained using Thomas, Clark, and Yoon-Nelson models.

Antibiotic Resistance in the Drinking Water: Old and New Strategies to Remove Antibiotics, Resistant Bacteria, and Resistance Genes

Bacterial resistance is a naturally occurring process. However, bacterial antibiotic resistance has emerged as a major public health problem in recent years. The accumulation of antibiotics in the environment, including in wastewaters and drinking water, has contributed to the development of antibiotic resistant bacteria and the dissemination of antibiotic resistance genes (ARGs). Such can be justified by the growing consumption of antibiotics and their inadequate elimination. The conventional water treatments are ineffective in promoting the complete elimination of antibiotics and bacteria, mainly in removing ARGs. Therefore, ARGs can be horizontally transferred to other microorganisms within the aquatic environment, thus promoting the dissemination of antibiotic resistance. In this review, we discuss the efficiency of conventional water treatment processes in removing agents that can spread/stimulate the development of antibiotic resistance and the promising strategies for water remediation, mainly those based on nanotechnology and microalgae. Despite the potential of some of these approaches, the elimination of ARGs remains a challenge that requires further research. Moreover, the development of new processes must avoid the release of new contaminants for the environment, such as the chemicals resulting from nanomaterials synthesis, and consider the utilization of green and eco-friendly alternatives such as biogenic nanomaterials and microalgae-based technologies.

Adsorption and detoxification of pharmaceutical compounds from wastewater using nanomaterials: A review on mechanism, kinetics, valorization and circular economy

Antibiotics overuse, inappropriate conduct, and discharge have led to adverse effects on various ecosystems. The occurrence of antibiotics in surface and drinking water is a matter of global concern. It is responsible for multiple disorders, including disruption of endocrine hormones and high chronic toxicity. The hospitals, pharmaceutical industries, households, cattle farms, and aquaculture are the primary discharging sources of antibiotics into the environment. This review provides complete detail on applying different nanomaterials or nanoparticles for the efficient removal of antibiotics from the diverse ecosystem with a broader perspective. Efforts have been made to focus on the degradation pathways and mechanism of antibiotic degradation using nanomaterials. More light has been shed on applying nanostructures in photocatalysis, which would be an economical and efficient solution. The nanoscale material or nanoparticles have incredible potential for mineralizing pharmaceutical compounds in aqueous solutions at low cost, easy handling characteristics, and high efficacy. Furthermore, nanoparticles can absorb the pharmaceutical by-products and wastes at a minimum cost as they can be easily recycled. With the increasing number of research in this direction, the valorization of pharmaceutical wastes and by-products will continue to expand as we progress from old conventional approaches towards nanotechnology. The utilization of nanomaterials in pharmaceutical wastewater remediation is discussed with a major focus on valorization, energy generation, and minimization and its role in the circular economy creating sustainable development.

Efficient Adsorption of Tetracycline from Aqueous Solutions by Modified Alginate Beads after the Removal of Cu(II) Ions

This work dealt with a potential and effective method to reuse modified alginate beads after the removal of Cu(II) ions for efficient adsorption of tetracycline (TC) from aqueous solutions. The modified alginate beads were fabricated by a polyacrylamide (PAM) network interpenetrated in alginate-Ca2+ network (PAM/CA) decorated with polyethylene glycol as a pore-forming agent. The porous PAM/CA was characterized using scanning electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The adsorption kinetics, isotherms, adsorption stability, and reusability studies of the adsorbent toward Cu(II) ions were scrutinized. The column performance of porous PAM/CA was tested with Cu(II)-containing electroplating wastewater. After Cu(II) adsorption, the Cu(II)-adsorbed PAM/CA (PAM/CA@Cu) was applied to remove TC from aqueous solutions without any regeneration process. The effects of pH, initial TC concentration, ionic strength, and coexisting ions on the adsorption were also discussed in detail. Compared with many reported adsorbents, the PAM/CA@Cu exhibited an excellent adsorption performance toward TC with a maximum adsorption capacity of 356.57 mg/g predicted by the Langmuir model at pH 5.0 and 30 °C with the absence of coexisting ions. The possible adsorption mechanism of TC onto the PAM/CA@Cu was revealed.

Removal of dye using peroxidase-immobilized Buckypaper/polyvinyl alcohol membrane in a multi-stage filtration column via RSM and ANFIS

The feasibility and performance of Jicama peroxidase (JP) immobilized Buckypaper/polyvinyl alcohol (BP/PVA) membrane for methylene blue (MB) dye removal was investigated in a customized multi-stage filtration column under batch recycle mode. The effect of independent variables, such as influent flow rate, ratio of H₂O₂/MB dye concentration, and contact time on the dye removal efficiency, were investigated using response surface methodology (RSM). To capture the inherent characteristics and better predict the removal efficiency, a data-driven adaptive neuro-fuzzy inference system (ANFIS) is implemented. Results indicated that the optimum dye removal efficiency of 99.7% was achieved at a flow rate of 2 mL/min, 75:1 ratio of H₂O₂/dye concentration with contact time of 183 min. The model predictions of ANFIS are significantly good compared with RSM, thus resulting in R² values of 0.9912 and 0.9775, respectively. The enzymatic kinetic parameters, K_m and V_max, were evaluated, which are 1.98 mg/L and 0.0219 mg/L/min, respectively. Results showed that JP-immobilized BP/PVA nanocomposite membrane can be promising and cost-effective biotechnology for the practical application in the treatment of industrial dye effluents.

Tetracycline removal by polyelectrolyte copolymers in conjunction with ultrafiltration membranes through liquid-phase polymer-based retention

In this study, we used a liquid-phase polymer-based retention technique assisted by polyelectrolyte copolymers containing quaternary ammonium and sulfonate groups that are capable of removing the antibiotic tetracycline (TC) through electrostatic interactions. The polymers were synthesized using zwitterionic, anionic, and cationic monomers with the aim of obtaining copolymers with different charge balances at the ratios of 1:1, 2:1, and 1:2 (negative: positive). The parameters investigated for each copolymer included the pH, ionic strength, concentration of polymer, maximum retention capacity, and sorption-elution process at pH 11.0 and 3.0. The copolymers with a charge ratio of 1:2 achieved the highest retention (80.0%) at alkaline pH, while the copolymers with charge ratios of 2:1 and 1:1 exhibited the maximum retention (72.0%) at acidic pH. Based on these results, the pH and charge of the polyelectrolyte copolymers play important roles in the TC removal processes. Additionally, the maximum retention capacity (MRC) recorded was 731.2, 176.8, and 214.8 mg TC/g of copolymer in the first charge for the three copolymer polyelectrolytes, and the second charge of the MRC process did not improve compared with the first load.