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In the present study, the adsorption behavior of ciprofloxacin (CIP) from aqueous solution onto MWCNTs/Al2O3 was studied using batch experiments. Physical characterization of MWCNTs/Al2O3 was determined by SEM, XRD, and BET. The effective parameters investigated included: initial CIP concentration, contact time, MWCNTs/Al2O3 mass, and temperature. Based on experimental results and correlation coefficients, the rate of CIP adsorption followed the pseudo-second-model kinetics. Complete compatibility of the adsorption isotherm process was achieved with the Langmuir model, and the maximum adsorption capacity reached 41.73 mg/g under the optimized conditions (pH = 7, MWCNTs/Al2O3 dose = 1.2 g/L, contact time = 60 min, initial concentration = 10 mg/L, and temperature= 45 °C). The adsorption capacities based on the Langmuir model at different temperatures, 273, 288, 303, and 318 K, were equal to 72.18, 75.92, 79.65, and 83.47 mg/g, respectively. The determined parameters of the thermodynamic studies demonstrated the endothermic and spontaneous nature of the biosorption. The mean free energy was estimated from D–R isotherm model to be 0.316–0.707 KJ/mol, which clearly proved that the adsorption experiment followed a physical process. The data suggest that MWCNTs/Al2O3 could be used as a highly effective adsorbent material with a high capacity for the removal of antibiotics from water and wastewater. [ABSTRACT FROM AUTHOR]

In recent years, there has been growing awareness that by 2050, many countries will experience critical issues related to water scarcity. The need to recycle/reuse wastewater after pollution treatment is a major concern worldwide for ensuring water security at the national level. Treatment technologies to remove major pollutants, namely, heavy metals, anionic impurities and the vast range of organic compounds, have received substantial attention from the scientific community. Water resource pollution is increasing due to an increasing world population and its corresponding activities. Amongst the different technologies used to decrease pollutant levels in water, adsorption technology is highly effective even at low pollutant concentrations. Carbonaceous materials and their composites have been widely used due to their unique surface properties and high adsorption capacities, but better adsorbents with higher pollutant adsorption capacities and faster uptake are still needed. Recently, the development of graphene-based adsorbents, with their highly active surfaces and large surface areas, has created much excitement. Therefore, an updated review is needed to summarize this graphene research. This review provides a summary of the literature in the field of adsorptive removal of organics from water, with a focus on phenols and dyestuffs. The synthesis methods, characterization techniques, adsorption behaviors, experimental parameters, mechanisms, thermodynamics, the effect of coexisting ions and regeneration–desorption processes are considered. Finally, research challenges and knowledge gaps – limited regeneration and solute recovery studies, the behavior of mixed pollutants effluents, designing graphenic adsorbents for specific pollutants, treatment system economic analyses - in the field are discussed. [Display omitted] • Modified graphene oxide, MGO, reviewed for phenols and dye removal. • Equilibrium isotherm analyses and adsorption kinetic models are reviewed. • MGO adsorption showed rapid kinetics reaching 90% capacity under 5 min. • The MGO capacities compared very favorably with alternative adsorbent capacities. • Gaps in the literature studies and the direction of future studies are presented. [ABSTRACT FROM AUTHOR]

Novel fixed-bed adsorption investigations applying carbon nanotube (CNT) coated poly-amidoamine dendrimer (PAMAM) as an adsorbent have been studied for the adsorption of As(III) as arsenous acid, Co 2+ , and Zn 2+ from aqueous solution. FTIR, SEM, 1 H NMR, TGA, TEM, Raman Spectra and zeta potential measurements have been employed for characterizing the synthetic nanocomposite and these techniques indicated that the dendrimer functionalized CNTs have been favorably synthesized. The effects of process parameters including flow rate, initial concentration and bed height on the duration of the breakthrough time, mass transfer zone, adsorption capacity and exhaustion time at breakthrough were investigated. Decreasing initial concentration and flow rate, and increasing bed height, increased the exhaustion and breakthrough times. In addition, the removal capacity at breakthrough was enhanced with decreasing flow rate, initial ion concentration and increasing bed height. The notably high maximum adsorption capacities at fixed bed breakthrough of the studied ions were 432 mg/g for As(III) as arsenous acid, 494 mg/g for Co 2+ , and 470 mg/g for Zn 2+ at bed height of 12.0 cm, influent concentration of 100 mg/L and flow rate of 0.5 mL/min. Almost no previous fixed bed data for PAMAMS exist. Adsorption results were correlated using the Thomas, Yoon-Nelson, and Bohart-Adams models. Empirical breakthrough curves were found to be best fitted with the predicted curves produced by the Thomas and Yoon-Nelson equations. This study illustrates the efficiency of PAMAM/CNT nanocomposite for the adsorption of As(III), Co 2+ , and Zn 2+ from aqueous solution. [ABSTRACT FROM AUTHOR]

Sludge, a byproduct produced from numerous industrial activities, has been recognized as an ecological burden for the society. However, viewing the sludge, as a carbon-rich material, has stimulated new gateways for the production of porous activated carbons for water treatment applications. Herein, various textural properties of the sludge-based activated carbons have been compiled and critically reviewed with the focus on surface area, pore size and pore size distribution for both physically and chemically activated carbons. It has been found that chemical activation using various activating agents yields more superior adsorbents with high specific surface areas than physical activation methods. Moreover, the potential of sludge-derived activated carbons for the sequestration of metals and dyes from aqueous media has been discussed. Furthermore, the adsorption mechanism in several adsorbent–adsorbate systems and the effect of various parameters on the adsorption behavior of different dyes and metals on sludge-based activated carbons have been reviewed. It has been shown that the pollutant uptake capacities of the adsorbents derived from sewage sludge are not only governed by the textural properties of the adsorbents, but also by their surface properties, such as the functional groups and the surface charge and thus it is proposed that both of these crucial factors be considered concurrently. [ABSTRACT FROM AUTHOR]