Removal of Zinc(II) from municipal wastewater using chemically modified activated carbon developed from Rice husk and Kikar charcoal

Abstract

Heavy metals in municipal wastewater are of utmost concern for researchers and environmental agencies due to their adverse effect to the ecosystem. Various technologies were practiced for the removal of heavy metals; however, adsorption is one the most interesting technique for its low cost, simple operation and reasonable efficiency. In this study, removal of Zinc (II) from municipal wastewater in Quetta city of Pakistan was investigated by using activated carbon (AC) developed from Rice Husk (RH) and Kikar Charcoal (KC). Char were made by heating KC and RH in a tubular reactor at 700 o C under N2 gas flow. Furthermore, Char material obtained were activated using H2SO4 as an activating agent to increase the surface area and porosity of the char materials. The biochar adsorbents were characterized using SEM, EDX and BET techniques. To identify the efficiency of adsorbents, the wastewater samples collected from Shahbaz town area of Quetta city were treated using different particle size of AC (180 and 300 µm) and varying adsorbate dose (0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7 g/50 mL), pH of the solution (3, 4, 5, 6, 7), respectively. The results showed that increase in the mass of adsorbents had a direct relation with the removal efficiency of Zn(II). The maximum removal efficiency for zinc (II) was found to be 99 % and 72.34 % for KC and RH based ACs at adsorbent dose 0.7 g/50mL and pH 6, respectively. A small difference has been observed between the efficiencies of both ACs this was due to the difference between their surface area and porosity. While studying isotherm models the data was best fit with Langmuir isotherm model. The amount of zinc in the treated wastewater was recorded well enough under the standard limits provided by Environmental protection agency (EPA). This technique of treating municipal wastewater by using inexpensive biomass as adsorbent found to be very efficient and environmental friendly.