A novel adsorbent, NC-PEG, obtained by modification of nanocellulose (NC) with PEG-6-arm amino polyethylene glycol (PEG-NH 2) via maleic anhydride (MA) linker, was used for removal of Cd 2+ and Ni 2+ from water. A subsequent precipitation of iron oxide (FO) from goethite on NC-PEG was employed to produce NC-PEG/FO adsorbent which was used for As(V) and As(III) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on the adsorption efficiency were studied. The maximum adsorption capacities found for Cd 2+ and Ni 2+ , obtained by the use of Langmuir model, were 37.9 and 32.4 mg g-1 at 25 °C, respectively. Also, high As(V) and As(III) removal capacities of 26.0 and 23.6 mg g-1 were obtained. The thermodynamic parameters indicated endothermic, feasible and spontaneous nature of the adsorption process. The kinetic study, i.e., fitting by Weber-Morris model predicted that intra-particle diffusion was the ratecontrolling step. The ability for multi-cycle reusability of both NC-PEG and NC-PEG/FO, represents a positive indicator when considering their possible applications.
The multistage synthesis of the multi-wall carbon nanotubes (MWCNT) modified with polyamidoamine dendrimers, A1/ and A2/MWCNT, capable of cation removal, is presented in this work, as well as novel adsorbents based on these precursor materials and modified with goethite nano-deposit, α-FeOOH, A1/ and A2/MWCNT-α-FeO(OH) adsorbents used for As(V) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on adsorption efficiency were studied. Adsorption data modelling by the Langmuir isotherm, revealed good adsorption capacities (in mg g-1) of 18.8 for As(V) and 60.1 and 44.2 for Pb 2+ and Cd 2+ on A2/MWCNT, respectively. Also, 27.6 and 29.8 mg g-1 of As(V) on A1/ and A2/MWCNT-α-FeO(OH), respectively, were removed. Thermodynamic parameters showed that the adsorption is spontaneous and endothermic processes. Results of the study of influences of competitive ions: bicarbonate, sulfate, phosphate, silicate, chromate, fluoride and natural organic matter (NOM), i.e., humic acid (HA), showed the highest effect of phosphate on the decrease of arsenate adsorption. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber-Morris model which predicted intra-particle diffusion as a rate-controlling step. Also, activation energy (E a / kJ mol-1): 8.85 for Cd 2+ , 9.25 for Pb 2+ and 7.98 for As(V), were obtained from kinetic data.
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