Removal of heavy metals from water using multistage functionalized multiwall carbon nanotubes

Abstract

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, alpha-FeOOH, A1/ and A2/MWCNT-alpha-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 Pb2+ and Cd2+ on A2/MWCNT, respectively. Also, 27.6 and 29.8 mg g(-1) of As(V) on A1/ and A2/MWCNT-alpha-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 Cd2+, 9.25 for Pb2+ and 7.98 for As(V), were obtained from kinetic data.