Adsorption studies on the treatment of battery wastewater by purified carbon nanotubes (P-CNTs) and polyethylene glycol carbon nanotubes (PEG-CNTs)

Fe-Ni/kaolin catalyst was used for the production of carbon nanotubes (CNTs) via catalytic chemical vapour deposition followed by acid purification treatment and functionalization with polyethylene glycol to give purified carbon nanotubes (P-CNTs) and polyethylene glycol carbon nanotubes (PEG-CNTs), respectively. The as-synthesized CNTs, P-CNTs and PEG-CNTs were characterized by high-resolution transmission electron microscopy (HRTEM), high-resolution scanning electron microscopy (HRSEM), Fourier transform infrared and Brunauer Emmett Teller (BET). The adsorption behaviour P-CNTs and PEG-CNTs to remove specifically Cr and Zn from battery wastewater were examined by the batch adsorption process as a function of different contact time, adsorbent dosage and temperature. The HRSEM/HRTEM/BET analysis confirmed that both nano-adsorbents were tube-like in nature, high porosity and crystalline, with PEG-CNTs possessing high surface area (970.81 m(2)/g) than P-CNTs (781.88 m(2)/g). The optimum contact time and adsorbent dosage to remove Cr and Zn by P-CNTs and PEG-CNTs were 90 and 50 min and 0.3 g, respectively. Under the applied conditions, PEG-CNTs exhibited high adsorption capacity than P-CNTs for the selected heavy metals. The adsorption equilibrium data were better fitted to the Freundlich model while the kinetic data conformed to the pseudo-second-order model. Thermodynamic studies demonstrated the feasibility and endothermic nature of the system. This study demonstrated that both nano-adsorbents purify battery wastewater and with better performance by PEG-CNTs.