Adsorption of arsenic from simulated groundwater using treated laterite as adsorbent

• Main Author: Sihombing, Amsal G.
• Format: text
• Language: English
• Published: Animo Repository 2008
• Subjects: Arsenic; Water > Pollution; Laterite; Water contamination; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3768; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/10606/viewcontent/CDTG004561_P.pdf
• Institution: De La Salle University

Arsenic contamination in groundwater is a major problem which is occurring globally. The issue is more urgent for people living in rural and poor areas with arsenic-contaminated water source for the lack of efficient and cost effective water treatment technology. Based on this consideration, laterite, a weathering rock product, had been investigated as an inexpensive and effective arsenic adsorbent. Three types of laterite (labeled as L1, L2, and L3) which are locally available in the Philippines were used as arsenic adsorbent, of which laterite with the highest adsorption capacity was subjected to further treatment. The treatment included mixing the laterite with three different binding solutions, namely distilled deionized (DD) water, hydrochloric acid (HCl), and sodium hydroxide (NaOH), after which the treated laterite was calcined at different temperatures of 400, 550, and 700 °C. Results showed that laterite from the Philippines were able to reduce arsenic concentration from 240 ppb to a concentration less than 10 ppb. The best removal efficiency was achieved by laterite with akaganeite as the major component in laterite (L1). The addition of strong acid (HCl 30% (w/w)) or base (NaOH at 6M) followed by calcination altered the mineral constituent of the laterite. Magnetite was found to be the final iron phase after the said treatment. Treatment on laterite also improved the durability of the laterite soil which was reflected from the Total Suspended Solid (TSS) concentration before and after the treatment. The concentration of Total Suspended Solid in water samples with untreated laterite was 12 mg/L while with treated laterite was below 1 mg/l. The results showed that the treatment increased the durability of the laterite which could reduce the burden of filtration step. In this study, addition of HCl 30% (w/w), calcined at 700°C for 4 hour was found as the best condition among the tested parameters. Laterite treated at the best condition reduced the arsenic concentration from 240 ppb to less than 10 ppb. ii Equilibrium study showed that arsenic adsorption on laterite L1 followed Freundlich isotherm model and the maximum adsorption capacity was found to be 1.4729 Ag As/g adsorbent.