Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite

摘要

Acid-activated laterite (AAL) is used to remove arsenic from synthetic and natural groundwater. Physi-cochemical characteristics of AAL, such as BET (Brunauer-Emmett-Teller) surface area, pore volume, pore volume distribution, zero point of charge, and chemical composition, are studied and compared with raw laterite (RL). The BET surface area and pore volume of AAL are obtained as 45.4 ±2.7 m~2 g~(-1) and 0.063 ± 0.007 mL g~(-1), respectively. Zero point of charge of AAL is found to be 5.70 ± 0.22. Arsenite and arsenate adsorption on AAL are examined under varying process parameters such as adsorbent dose, contact time, temperature, particle size, initial arsenic concentration, and competitive ions in batch mode. Arsenic adsorption capacity of AAL increases by two- to threefold compared with RL. The kinetic data fit better to pseudo-second-order model. Transport properties, such as external mass transfer coefficient and effective pore diffusivity of arsenic species, are obtained from shrinking core model fit to experimental kinetic data. Continuous fixed bed column mode adsorption of arsenic on AAL is performed. About 200 bed volume (21 L) of arsenic contaminated groundwater (total arsenic: 378 ± 8.9 μg L~(-1)) has been treated at a breakthrough concentration of 50 μg L~(-1) of arsenic by using column height of 20 cm (weight of adsorbent: 125 g).