| Iron oxide-coated sand is a potential adsorbent for anion and cation removal from water and wastewater. However, the type of iron oxide formed on the sand depends on several factors including the physical and chemical environment in which the iron oxide was prepared and coated. The present study involved an investigation on the effects of seven factors such as coating pH, temperature, iron concentration, number of coatings, ageing, pH of the solution and mass of the adsorbent on arsenic (V) and arsenic (III) removal from water using two sets of 27-4 (2 level) fractional factorial design. The results showed that coating pH, temperature and solution pH had the greatest effect on As(V) removal, while coating pH, temperature, solution pH and mass of adsorbent had the greatest effect on As(III) removal. The effects of other factors were relatively small on arsenic removal. Hence, these significant factors were the focus of further studies.; Batch studies were conducted to investigate and compare the adsorption properties of coated sand prepared at coating pH (pHc) 2, 4, 6, and 8 and temperatures of 110°C, 300°C, and 550°C. These studies showed that the coated sand at pHc 2 and 110°C had better arsenic removal capacity (94.3% and 94.7% for As(V) and As(III), respectively) compared with other coating conditions. Isotherm studies showed that the adsorption capacity of the sand coated at pHc 2 and 110°C was 99.3 mug/g and 271 mug/g for As(V) and As(III), respectively. |
