Mechanism of sonication time on structure and adsorption properties of 3D peanut shell/graphene oxide aerogel

Environmental remediation of the norfloxacin in water by adsorption: Advances, current status and prospects

Antibiotics are considered as the new generation water pollutants as these disturb endocrine systems if water contaminated with antibiotics is consumed. Among many antibiotics norfloxacin is present in various natural water bodies globally. This antibiotic is considered an emerging pollutant due to its low degradation in aquatic animals. Besides, it has many side effects on human vital organs. Therefore, the present article discusses the recent advances in the removal of norfloxacin by adsorption. This article describes the presence of norfloxacin in natural water, consumption, toxicity, various adsorbents for norfloxacin removal, optimization factors for norfloxacin removal, kinetics, thermodynamics, modeling, adsorption mechanism and regeneration of the adsorbents. Adsorption takes place in a monolayer following the Langmuir model. The Pseudo-second order model represents the kinetic data. The adsorption capacity ranged from 0.924 to 1282 mg g-1. In this sense, the parameters such as the NFX concentration added to the adsorbent textural properties exerted a great influence. Besides, the fixed bed-based removal at a large scale is also included. In addition to this, the simulation studies were also discussed to describe the adsorption mechanism. Finally, the research challenges and future perspectives have also been highlighted. This article will be highly useful for academicians, researchers, industry persons, and government authorities for designing future advanced experiments.

Systematic review: External carbon source for biological denitrification for wastewater

Nitrogen mitigation is serious environmental issue around the globe. Several methods for wastewater treatment have been introduced, but biological denitrification has been recommended, particularly with addition of the best external carbon source. The key sites of denitrification are wetlands; it can be carried out with different methods. To highlight the aforementioned technology, this paper deals to review the literature to evaluate biological denitrification and to demonstrate cost effective external carbon sources. The results of systematic review disclose the denitrification process and addition of different external carbon sources. The online literature exploration was accomplished using the most well-known databases, that is, science direct and the web of science database, resulting 625 review articles and 3084 research articles, published in peer-reviewed journals between 2015 and 2021 were identified in first process. After doing an in-depth literature survey and exclusion criteria, we started to shape the review from selected review and research articles. A number of studies confirmed that both nitrification and denitrification are significant for biological treatment of wastewater. The studies proved that the carbon source is the main contributor and is a booster for the denitrification. Based on the literature reviewed it is concluded that biological denitrification with addition of external carbon source is cost effective and best option in nitrogen mitigation in a changing world. Our study recommends textile waste for recovery of carbon source.

Development and Evaluation of Cellulose/Graphene-Oxide Based Composite for Removing Phenol from Aqueous Solutions

In this study, a graphene oxide/cellulose composite (GO-cellulose) was prepared usingcellulose and graphene oxide (GO) through ultrasonication, followed by the freeze-dried method. The Brunauer-Emmett-Teller (BET) specific surface area of GO-cellulose (~6.042 m²/g) was higher compared to cellulose (1.023 m²/g).The UV-Visible spectraindicated that the prepared GO-cellulose composite removedphenol efficiently from aqueous solutions with high adsorption power. The effectiveness of the composite for phenol adsorption was examinedunder diverse conditions.The results reveal that the composite optimally improved the adsorption at pH 7 with a dose of 0.125 g/30 L in about 40 min. The adsorption process showed that in optimum conditions, 86 ± 2% of phenol was removed in 40 min with an adsorption capacity of 6.192 mg g^-1. The adsorption behavior was well fitted to the pseudo-second-order kinetic model and the Langmuir isotherms at all temperatures.The present study suggests that synthesized GO-cellulose is useful inthe removal of phenol pollutants from aqueous solutions.

A review of the adsorption method for norfloxacin reduction from aqueous media

Norfloxacin (NRFX) is one of a class of antibiotics known as broad-spectrum fluoroquinolone antibiotic that is frequently used to treat infectious disorders in both animals and humans. NRFX is considered an emergent pharmaceutical contaminate. This review's objective is to evaluate empirical data on NRFX's removal from aqueous medium. The environmental danger of NRFX in the aquatic environment was validated by an initial ecotoxicological study. Graphene oxide/Metal Organic Framework (MOF) based composite, followed by Magnesium oxide/Chitosan/Graphene oxide composite gave the highest NRFX adsorption capacities (Qmax) of 1114.8 and 1000 mg/g, respectively. The main adsorption mechanisms for NRFX uptake include electrostatic interactions, H-bonds, π-π interactions, electron donor-acceptor interactions, hydrophobic interactions, and pore diffusion. The adsorptive uptake of NRFX were most suitably described by Langmuir isotherm and pseudo-second order implying adsorbate-to-adsorbent electron transfer on a monolayer surface. The thermodynamics of NRFX uptake is heavily dependent on the makeup of the adsorbent, and the selection of the eluent for desorption from the solid phase is equally important. There were detected knowledge gaps in column studies and adsorbent disposal method. There's great interest in scale-up and industrial applications of research results that will aid in management of water resources for sustainability.

Fabrication of superhydrophobic Enteromorpha-derived carbon aerogels via NH4H2PO4 modification for multi-behavioral oil/water separation

Hydrophobic and oleophilic biomass-based block materials are considered to be highly promising candidates used for oil/water separation. However, the crucial hydrophobic modification process often involves various toxic and hazardous organic substances or requires high energy inputs. Inspired by the flame retardant principle of phosphorus-containing flame retardants, herein, an Enteromorpha-derived carbon (ADP-EP) aerogel with a water contact angle of 144.2° was prepared by successive freeze-shaping, freeze-drying and low-temperature carbonization treatment (300 °C), using NH₄H₂PO₄ (ADP) as a modifier. The results demonstrated that the introduction of NH₄H₂PO₄ could largely facilitate the removal of oxygenated groups from the pristine EP aerogels and enhance their surface roughness, thereby achieving surface hydrophobic modification. Featuring intrinsic low density, rich porosity and strong lipophilicity, the as-fabricated ADP-EP aerogels exhibited exceptional performance in both oil spill adsorption (~140 g/g) and water-in-oil emulsion separation. Moreover, the good reusability for oil uptake was also realized thanks to its robust mechanical compressibility and thermal stability. This work provides a facile, economical and eco-friendly route to obtain a desirable hydrophobic/oleophilic surface.

Synthesis of a highly recoverable 3D MnO2/rGO hybrid aerogel for efficient adsorptive separation of pharmaceutical residue

Water contamination by non-steroidal anti-inflammatory drugs, such as acetaminophen, is an emerging ecological concern. In this study, a new three-dimensional manganese dioxide-engrafted reduced graphene oxide (3D MnO₂/rGO) hybrid aerogel was developed for acetaminophen sequestration. The synthesis involved firstly the self-assembly of GO aerogel, followed by thermal reduction and in-situ MnO₂ growth by redox-reaction. The aerogel demonstrated interlinked planes with smooth surfaces deposited with MnO₂ nanospheres and pores of 138.4 - 235.3 µm width. The influences of adsorbent dosage, initial pH, acetaminophen concentration, temperature and contact time were investigated. It was determined that the adsorption of acetaminophen occurred on uniform sorption sites in the aerogel, as suggested by the best fit of data to the Langmuir isotherm, yielding a maximum adsorption capacity of 252.87 mg/g. This highest adsorption performance of the 3D MnO₂/rGO aerogel was attained at a dosage of 0.6 g/L, initial pH of 6.2 and temperature of 40°C. The process kinetics were in-line with the pseudo-first-order and pseudo-second-order kinetics at 10 and 20 - 500 mg/L concentrations, respectively. Thermodynamic assay showed the spontaneity and endothermicity features of the 3D MnO₂/rGO-acetaminophen system. The acetaminophen adsorption mechanisms were mainly hydrogen bonding and pore entrapment. Moreover, the as-synthesised aerogel was effectively regenerated using acetone and re-utilised in four adsorption-desorption cycles. Overall, the results highly recommend the implementation of the 3D MnO₂/rGO hybrid aerogel for purification of wastewater polluted by acetaminophen residue.

One-step synthesis of garlic peel derived biochar by concentrated sulfuric acid: Enhanced adsorption capacities for Enrofloxacin and interfacial interaction mechanisms

This study put forward a one-step carbonization method by concentrated sulfuric acid to prepare garlic peel derived biochar, and the synthetic conditions were optimized by L₁₆(4⁵) orthogonal experiments. Notably, in order to study the differences between the proposed synthetic method and the conventional pyrolysis method, the concentrated sulfuric acid carbonized garlic peels biochar (CSGPB) was compared with pyrolysis derived garlic peel biochar (HTGPB) in characterization and adsorption capacities for Enrofloxacin (ENR). Results showed that CSGPB exhibited more graphite-like structures with more active functional groups on the surface, and the equilibrium adsorption capacity of CSGPB (142.3 mg g^-1) was 13.7 times of HTGPB (10.4 mg g^-1) under identical conditions. Moreover, the adsorption behaviors including adsorption kinetics, isotherms and thermodynamics of CSGPB for ENR were fully investigated and discussed. Based on the above experiments, density functional theory (DFT) simulations were performed to reveal the interfacial interaction and adsorption mechanism. Results showed π-π interaction between quinolone moieties of ENR and graphite-like structures in CSGPB might be the dominant mechanism. As for the functional groups, the adsorption energies were -40.46, -15.21 and -5.96 kJ mol^-1 for -SO₃H, -OH and -COOH, respectively, which indicated -SO₃H was the most active functional groups on the surface of CSGPB. This study provided a new sustainable perspective for the design of efficient biochars, and explored the interfacial interaction mechanism of antibiotics removal on biochars.

Enhanced removal of phosphate using pomegranate peel-modified nickel‑lanthanum hydroxide

In this work, a bimetallic Ni/La nanoparticle-laded biosorbent was fabricated from pomegranate fibers by solvothermal synthesis method. The material exhibited a high-efficient phosphate removal capability. The results of the characterization analysis showed that the surface of pomegranate fibers was rough and evenly coated with Ni and La after modification, and the specific surface area of Ni-La@Peel increased to 50.20 m²/g, providing a large number of adsorption sites for phosphate removal. The maximum phosphate removal rate of adsorbent was higher than 97% in a wide pH range (3.7-10.8). The maximum adsorption capacities of Ni-La@Peel were 226.55 mg-P/g and 220.31 mg-P/g under alkaline and acidic conditions, respectively, as calculated using the Langmuir model. Meanwhile, all the results were consistent with the Langmuir isothermal (R² = 0.99) and kinetic pseudo-second order models (R² = 0.99), indicating that the phosphate removal mechanism of Ni-La@Peel was mainly related to homogeneous chemisorption. Experimental results showed that in the presence of other anions, such as chloride, sulfate, nitrate, bromide and fluoride, the adsorption capacity of phosphate was only reduced by about 10% compared to the blank sample individually. In addition, the phosphate removal efficiency of Ni-La@Peel remained 82.05% at 7th adsorption-desorption cycle. These findings show that Ni-La@Peel is a promising material for purification of phosphate-containing wastewater.

Preparation of a rice straw-based green separation layer for efficient and persistent oil-in-water emulsion separation

Inefficiency, high cost, and complex operation have emerged as shackles for large-scale separate oil-in-water emulsion. Herein, a low-cost and eco-friendly separation layer with a rough structure and rich anionic groups was fabricated from rice straw (RS) via a simple acid-base treatment and slight squeeze process. The separation layer's morphology, composition, and wettability were investigated. It was then employed to separate oil-in-water emulsion. The RS after acid and alkali treatment (A₁A₂-RS) exhibited a clear fiber structure and abundant humps, which made the separation layer superwettable and highly electronegative (-26.55 mV). The overlapped and intertwined A₁A₂-RS layer structure owned a superior performance for hexadecyl-trimethyl-ammonium-bromide (CTAB) adsorption and tiny oil interception. As a result, the separation layer had stable fluxes (>500 LMH) for multiple CTAB-stabilized emulsions and the obtained filtrates performed low total organic carbon (TOC) contents (<30 mg/L). In addition, the A₁A₂-RS layer had excellent renewability (10 cycles/ 200 mL) and the flux could be substantially recovered merely by aqueous wash. Moreover, filtrate analysis showed that the A₁A₂-RS layer had a good effect on actual emulsion treatment with a TOC removal rate of 89.56%.

Porous Aerogels and Adsorption of Pollutants from Water and Air: A Review

Aerogels are open, three-dimensional, porous materials characterized by outstanding properties, such as low density, high porosity, and high surface area. They have been used in various fields as adsorbents, catalysts, materials for thermal insulation, or matrices for drug delivery. Aerogels have been successfully used for environmental applications to eliminate toxic and harmful substances-such as metal ions or organic dyes-contained in wastewater, and pollutants-including aromatic or oxygenated volatile organic compounds (VOCs)-contained in the air. This updated review on the use of different aerogels-for instance, graphene oxide-, cellulose-, chitosan-, and silica-based aerogels-provides information on their various applications in removing pollutants, the results obtained, and potential future developments.

Visible-LED-light-driven photocatalytic degradation of ofloxacin and ciprofloxacin by magnetic biochar modified flower-like Bi2WO6: The synergistic effects, mechanism insights and degradation pathways

Bi₂WO₆ possesses good stability but poor photocatalytic activity under visible light. Herein, the coupling of Bi₂WO₆, Fe₃O₄ and biochar (Bi₂WO₆/Fe₃O₄/BC) was investigated to enhance the photocatalytic performance of Bi₂WO₆ through facile hydrothermal method, which almost completely degraded ofloxacin (OFL) and ciprofloxacin (CIP) within 30 min under energy-saving visible LED irradiation. The superior photocatalytic activity of Bi₂WO₆/Fe₃O₄/BC was ascribed to the stronger visible light adsorption capacity and the lower recombination of electron-hole pairs. O₂^- played a major role during the photocatalytic reaction. The characterization results suggested that the introduction of biochar avoided the agglomeration of Bi₂WO₆ microspheres and Fe₃O₄ nanoparticles, at the same time, the biochar participated in OFL and CIP photodegradation by consuming different oxygen-containing functional groups. In order to further evaluate the application potential of Bi₂WO₆/Fe₃O₄/BC, the effects of environment factors and the application in different actual water were carefully investigated. Various transformation products and the possible degradation pathways of OFL and CIP were analyzed based on high resolution mass spectrometry (HRMS) results, moreover, the toxicity evaluation results of Escherichia coli indicated these intermediates products were less toxic compared OFL and CIP. Overall, Bi₂WO₆/Fe₃O₄/BC can provide a potential way for the application of photocatalytic technology in ambient wastewater purification.