Adsorption can be efficiently employed for the removal of various toxic dyes from water and wastewater. In this article, the authors reviewed variety of adsorbents used by various researchers for the removal of malachite green (MG) dye from an aqueous environment. The main motto of this review article was to assemble the scattered available information of adsorbents used for the removal of MG to enlighten their wide potential. In addition to this, various optimal experimental conditions (solution pH, equilibrium contact time, amount of adsorbent and temperature) as well as adsorption isotherms, kinetics and thermodynamics data of different adsorbents towards MG were also analyzed and tabulated. Finally, it was concluded that the agricultural solid wastes and biosorbents such as biopolymers and biomass adsorbents have demonstrated outstanding adsorption capabilities for removal of MG dye.

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Increasing amount of dyes in an ecosystem has propelled the search of various methods for dye removal. Amongst all the methods, adsorption occupies a prominent place in dye removal. Keeping this in mind, many adsorbents used for the removal of hazardous anionic azo dye Congo red (CR) from aqueous medium were reviewed by the authors. The main objectives behind this review article are to assemble the information on scattered adsorbents and enlighten the wide range of potentially effective adsorbents for CR removal. Thus, CR sorption by various adsorbents such as activated carbon, non-conventional low-cost materials, nanomaterials, composites and nanocomposites are surveyed and critically reviewed as well as their sorption capacities are also compared. This review also explores the grey areas of the adsorption performance of various adsorbents with reference to the effects of pH, contact time, initial dye concentration and adsorbent dosage. The equilibrium adsorption isotherm, kinetic and thermodynamic data of different adsorbents used for CR removal were also analysed. It is evident from a literature survey of more than 290 published papers that nanoparticle and nanocomposite adsorbents have demonstrated outstanding adsorption capabilities for CR. Graphical abstract ᅟ.

The ongoing COVID-19 pandemic increases the consumption of antimicrobial substances (ABS) due to the unavailability of approved vaccine(s). To assess the effect of imprudent consumption of ABS during the COVID-19 pandemic, we compare the 2020 prevalence of antidrug resistance (ADR) of Escherichia coli ( E. coli ) with a similar survey carried out in 2018 in Ahmedabad, India using SARS-CoV-2 gene detection as a marker of ABS usage. We found a significant ADR increase for in 2020 compared to 2018 in ambient water bodies, harbouring a higher incidence of ADR E.Coli towards non-fluoroquinolone drugs. Effective SARS-CoV-2 genome copies were found to be associated with the ADR prevalence. The prevalence of ADR depends on the efficiency of WWTPs (Wastewater Treatment Plants) and the catchment area in its vicinity. In year 2018 study, prevalence of ADR was discretely distributed, and the maximum ADR prevalence recorded was ~60%; against the current homogenous ADR increase, and up to 85% of maximum ADR among the incubated E.coli isolated from the river (Sabarmati) and lake (Chandola and Kankaria) samples. Furthermore, wastewater treatment plants showed less increase in comparison to the ambient waters, which eventually imply that although SARS-CoV-2 genes and faecal pollution may be diluted in the ambient waters, as indicated by low C t -value and E.coli count, the danger of related aftermath like ADR increase cannot be nullified. Also, Non-fluoroquinolone drugs exhibited overall more resistance than the quinolone drugs. Overall, this is probably the first ever study that traces the COVID-19 pandemic imprints on the prevalence of antidrug resistance (ADR) through wastewater surveillance and hints at monitoring escalation of other environmental health parameters. This study will make public and policyholders concerned about the optimum use of antibiotics during any kind of treatment.

In the present study, the biocompatible nanocomposite (nickel oxide nanoparticles loaded chitin beads (NiO NPs/CH)) was synthesized, characterized by using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis and then study its prospective application towards adsorption of malachite green (MG) dye. Further, batch studies were conducted to evaluate the adsorption capacity of nanocomposite, and the effects of various parameters, i.e., pH, adsorbate concentration, contact time, dosage of adsorbent and temperature, were investigated. The results revealed that the amount of MG adsorbed on the adsorbent increases with increasing initial dye concentration and by decreasing temperature. The equilibrium MG adsorption data on NiO NPs/CH were best described by the Langmuir isotherm model. Besides, the adsorption kinetics followed pseudosecond-order rate equation. Thermodynamic parameters such as free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated, and the results suggested that the adsorption process was spontaneous and exothermic in nature. Based on the results, it was concluded that the nanocomposite can be sustainably prepared and efficiently used for the adsorptive removal of MG from colored aqueous solutions.

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A B S T R A C TChitin (CH) and chitosan (CTS) beads used and compared for the adsorption of Congo Red (CR), an anionic azo dye, are reported in the present work. Initially, the adsorbents were prepared and characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) analysis. SEM images showed the heterogeneous and porous structure of the beads and FT-IR results confirm the presence of -OH, -NH 2 , and-NHCOCH 3 groups which are responsible for the adsorption of CR. Further, batch studies were conducted to evaluate the adsorption capacity of CH and CTS beads and the effects of the parameters like pH, adsorbate concentration, contact time, and dosage of adsorbents on adsorption were investigated. From the analysis, it was observed that the amount of CR adsorbed on both the adsorbents increases with increasing initial dye concentration and decreasing pH. The adsorption isotherms were analyzed using the Langmuir and Freundlich isotherms. The Langmuir isotherm was the best-fit adsorption isotherm model for the experimental data obtained from the non-linear chi-square statistic test. Further, the pseudo-first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The dynamical data fit well with the second-order kinetic model. The results indicate that CH and CTS beads could be employed as low-cost material for the adsorption of CR from wastewater.

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