Natural organic matter (NOM) is produced through metabolic reactions in water supply in drinking water sources and has been reported to cause several problems including objectionable taste and color ...of water, formation of disinfection by-products (DBPs) and reducing the amount of dissolved oxygen in water. The removal of NOM and its constituents from water is a challenging issue worldwide. Many technologies have been examined for this purpose. The properties and amount of NOM, however, can significantly affect the process efficiency. In the present work, an overview of the recent research studies dealing with adsorption method for the removal of NOM and related compounds from water is presented. A wide variety of conventional and non-conventional adsorbents have been reviewed for their potential in NOM removal from water. As revealed from the literature reviewed, modified adsorbents, composite materials and few nanomaterials have shown promising results for NOM removal from water. The main findings obtained for the removal of NOM using different adsorbents have been discussed in this review.
•Use of various adsorbents in NOM removal has been reviewed.•Influence of various parameters on NOM removal by adsorbents is discussed.•Mechanisms of NOM adsorption by different adsorbents are reviewed.
In recent decades, increased domestic, agricultural and industrial activities worldwide have led to the release of various pollutants, such as toxic heavy metals, inorganic anions, organics, ...micropollutants and nutrients into the aquatic environment. The removal of these wide varieties of pollutants for better quality of water for various activities is an emerging issue and a robust and eco-friendly treatment technology is needed for the purpose. It is well known that cellulosic materials can be obtained from various natural sources and can be employed as cheap adsorbents. Their adsorption capacities for heavy metal ions and other aquatic pollutants can be significantly affected upon chemical treatment. In general, chemically modified cellulose exhibits higher adsorption capacities for various aquatic pollutants than their unmodified forms. Numerous chemicals have been used for cellulose modifications which include mineral and organic acids, bases, oxidizing agent, organic compounds, etc. This paper reviews the current state of research on the use of cellulose, a naturally occurring material, its modified forms and their efficacy as adsorbents for the removal of various pollutants from waste streams. In this review, an extensive list of various cellulose-based adsorbents from literature has been compiled and their adsorption capacities under various conditions for the removal of various pollutants, as available in the literature, are presented along with highlighting and discussing the key advancement on the preparation of cellulose-based adsorbents. It is evident from the literature survey presented herein that modified cellulose-based adsorbents exhibit good potential for the removal of various aquatic pollutants. However, still there is a need to find out the practical utility of these adsorbents on a commercial scale, leading to the improvement of pollution control.
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•Various modification methods for cellulose-based adsorbents have been reviewed.•Potential of cellulose-based adsorbents in water treatment has been reviewed.•Current challenges and future perspectives in this direction have been presented.
Chitin and chitosan-derivatives have gained wide attention as effective biosorbents due to low cost and high contents of amino and hydroxyl functional groups which show significant adsorption ...potential for the removal of various aquatic pollutants. In this review, an extensive list of chitin- and chitosan-derivatives from vast literature has been compiled and their adsorption capacities for various aquatic pollutants as available in the literature are presented. This paper will give an overview of the principal results obtained during the treatment of water and wastewater utilizing chitin and chitosan-derivatives for the removal of: (a) metal cations and metal anions; (b) radionuclides; (c) different classes of dyes; (d) phenol and substituted phenols; (e) different anions and other miscellaneous pollutants. The review provides a summary of recent information obtained using batch studies and deals with the various adsorption mechanisms involved. It is evident from the literature survey that chitin- and chitosan-derivatives have shown good potential for the removal of various aquatic pollutants. However, still there is a need to find out the practical utility of such developed adsorbents on commercial scale.
Heterogeneous photocatalysis using Zn-Co-LDH@BC nanocomposite for degradation of GMF.
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•Hydrothermal preparation of novel and efficient Zn-Co-LDH@BC photocatalyst.•Superior ...photocatalytic activity of Zn-Co-LDH@BC for degradation of gemifloxacin.•High mineralization efficiency of gemifloxacin using Zn-Co-LDH@BC photocatalyst.•A plausible degradation pathway for photocatalytic degradation of gemifloxacin.•Reusability of Zn-Co-LDH@BC catalyst after five photocatalysis run.
The aim of the present study was to investigate the photocatalytic performance of biochar (BC)-incorporated Zn-Co-layered double hydroxide (LDH) nanostructures in gemifloxacin (GMF) degradation as a model pharmaceutical pollutant. The as-prepared Zn-Co-LDH@BC showed high photocatalytic efficiency due to the enhanced separation of photo-generated charge carriers using cobalt hydroxide as well as inhibiting the agglomeration of LDH nanostructures by incorporation of BC. According to the results, 92.7% of GMF was degraded through photocatalysis in the presence of Zn-Co-LDH catalyst. The photocatalytic performance of BC-incorporated Zn-Co-LDH was highly dependent on the solute concentration and photocatalyst dosage. The addition of ethanol caused more inhibiting effect than that of benzoquinone (BQ), indicating the major role of •OH in decomposition of GMF compared to the negligible role of O2•−. A greater enhancement in the photocatalytic degradation of GMF was obtained when the photoreactor containing Zn-Co-LDH@BC nanostructures was oxygenated. Less than 10% drop in the removal efficiency of GMF was observed within five successive operational runs. The results of chemical oxygen demand (COD) analysis indicated the COD removal efficiency of about 80% within 200 min, indicating the acceptable mineralization of GMF. The reaction pathways were also proposed for the photocatalytic conversion of GMF under UV light irradiation.
Rare earth elements (REEs) have gained considerable attention due to their unique properties and their use in huge range of industrial applications. They are widely used in different sectors such as, ...nuclear energy, metallurgy, medicine, chemical engineering, electronics, and computer manufacturing. As a result, the recovery of REEs is a significant issue that needs appropriate attention. There are many methods to recover REEs such as precipitation, filtration, solvent extraction etc. but these methods are not economically attractive. Among the available methods, adsorption has gained wider attention because of its simplicity, high efficiency and low cost. This review article presents the recently published literature (after 2013) regarding the removal of rare earth metals from aqueous solution by different low cost adsorbents. For this purpose, best applying model (isotherm, kinetic), thermodynamic studies and other factors which influence the adsorption process (such as the effect of solution pH, contact time, temperature and adsorbent's dose) are also discussed.
•Adsorbents for Rare earths recovery•Equilibrium, kinetic, thermodynamic modeling•Enthalpy-entropy compensation
► Various modification methods of activated carbon (AC) have been reviewed. ► Application of modified carbons in water treatment has been reviewed. ► Comparison of virgin and modified AC in ...pollutants removal has been discussed. ► Future perspectives in this direction have been proposed.
Activated carbon has been recognized as one of the oldest and widely used adsorbent for the water and wastewater treatment for removing organic and inorganic pollutants. The application of activated carbon in adsorption process is mainly depends on the surface chemistry and pore structure of porous carbons. The method of activation and the nature of precursor used greatly influences surface functional groups and pore structure of the activated carbon. Therefore, the main focus of researchers is to develop or modifies the activation/treatment techniques in an optimal manner using appropriate precursors for specific pollutants. In recent years, emphasis is given to prepare the surface modified carbons using different procedures to enhance the potential of activated carbon for specific contaminants. Various methods such as, acid treatment, base treatment, impregnation treatment, ozone treatment, surfactant treatment, plasma treatment and microwave treatment have been studied to develop surface modified activated carbons. In this paper, these modification methods have been reviewed and the potential of surface modified activated carbons towards water treatment has been discussed. This review article is aimed at providing precise information on efforts made by various researchers in the field of surface modification of activated carbon for water pollution control.
Adsorption process has been proven one of the best water treatment technologies around the world and activated carbon is undoubtedly considered as universal adsorbent for the removal of diverse types ...of pollutants from water. However, widespread use of commercial activated carbon is sometimes restricted due to its higher costs. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of waste materials as low-cost adsorbents is attractive due to their contribution in the reduction of costs for waste disposal, therefore contributing to environmental protection. In this review, an extensive list of low-cost adsorbents (prepared by utilizing different types of waste materials) from vast literature has been compiled and their adsorption capacities for various aquatic pollutants as available in the literature are presented. It is evident from the literature survey that various low-cost adsorbents have shown good potential for the removal of various aquatic pollutants. However, there are few issues and drawbacks on the use of low-cost adsorbents in water treatment that have been discussed in this paper. Additionally, more research is needed to find the practical utility of low-cost adsorbents on commercial scale.
In the present study, treated waste newspaper (TWNP) was used to remove chromium(VI) from aqueous solution using batch experiments. The adsorption parameters optimized were: initial Cr(VI) ...concentration (5, 20, 50mg/l), contact time (60min.), adsorbent dose (3.0g/L), and solution pH (3.0). The experimental data fitted well to Langmuir isotherm (R2=0. 98; maximum adsorption capacity 59.88mg/g.) and pseudo-second-order kinetic model. The rate constant k2 varied from 0.0019 to 0.0068 at initial Cr (VI) concentration from 5 to 20mg/L. It was observed that adsorption of Cr(VI) was pH dependent. The percentage removal of Cr(VI) was 59.88mg/g (64% at pH3). The results of the present study suggest that TWNP may be used as a low-cost adsorbent for the removal of chromium (VI) from aqueous solutions.
•TWNP can be considered as effective for removing chromium (VI) ion.•The adsorption of Cr(VI) ions onto newspapers was found to be highly pH-dependent.•The maximum Cr (VI) adsorption capacity (Qmax) was found 59.88mgg−1.•The results show that 72% of the adsorbed Cr (VI) was desorbed from TWNP.
In this study, desorption of Methylene blue (MB) dye from brown macroalga, Nizamuddinia zanardinii was investigated. Batch experiments were conducted to determine the effects of various operating ...parameters namely, the effect of seventeen different eluents, eluents concentrations, dye saturated alga weight, different HCl:1-butanol ratios, different particle sizes, different alga mass washing modes (after sorption experiment), initial dye concentration in the sorption experiment and contact time on the desorption efficiency of MB dye from brown macroalga. Among the seventeen eluents tested, hydrochloric acid (HCl) was found to be the most effective eluent for dye desorption. The mixture of 1 M HCl (25%):1 M 1-butanol (75%) was found to increase the dye desorption efficiency up to 63.67 ± 1.67%. Dye desorption percentage increased by increasing the alga particle sizes from <75 μm to >250 μm. The highest and lowest desorption efficiencies were attained by wet and dry masses after water washing by shaker, respectively. Both isotherm and kinetic data were obtained and fitted very well with the Sips isotherm model and pseudo-second-order kinetic model. After five sorption/desorption cycles, the dye sorption efficiency decreased from 96.99 ± 0.90% to 48.16 ± 1.98%, and the dye desorption efficiency decreased from 68.70 ± 2.03% to 46.83 ± 1.49%. Overall, this study has demonstrated that brown macroalga is a promising sorbent for the removal of MB dye from aqueous solutions.
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•Desorption of Methylene blue dye onto brown marine macroalga was studied.•Effects of different operating variables were examined during desorption.•Dye desorption percentage increased by increasing the alga particle sizes.•After five cycles, the desorption efficiency decreased from 68.7% to 46.8%.
A comparative study of the adsorbents prepared from several industrial wastes for the removal of 2-bromophenol, 4-bromophenol and 2,4-dibromophenol has been carried out. The results show that maximum ...adsorption on carbonaceous adsorbent prepared from fertilizer industry waste has been found to be 40.7, 170.4 and 190.2
mg
g
−1 for 4-bromophenol 2-bromophenol and 2,4-dibromophenol, respectively. As compared to carbonaceous adsorbent, the other three adsorbents (viz., blast furnace sludge, dust, and slag) adsorb bromophenols to a much smaller extent. This has been attributed to the carbonaceous adsorbent having a larger porosity and consequently higher surface area. The adsorption of bromophenols on this adsorbent has been studied as a function of contact time, concentration and temperature. The adsorption has been found to be endothermic, and the data conform to the Langmuir equation. The further analysis of data indicates that adsorption is a first order process. A comparative study of adsorption results with those obtained on standard activated charcoal sample shows that prepared carbonaceous adsorbent is about 45% as efficient as standard activated charcoal in removing bromophenols. To test the practical utility of this adsorbent, column operations were also carried out. The results were found satisfactory in removing bromophenols by column operations. Therefore, the present investigations recommend the use of carbon slurry waste as inexpensive adsorbent for small scale industries of developing/poor countries where disposal of solid waste of various industries and proper treatment of polluted wastewater is a serious problem.
