The investigation of As(V) removal mechanism using monosulfate ((Ca₄Al₂O₆(SO₄)·12H₂O) and its characteristics

Abstract

Experiments for As(V) removal using synthesized Ca‧Al-monosulfate was performed from the water contaminated with arsenate.Monosulfate is known as LDHs (Layered Double Hydroxides) which is one of the anionic clay minerals.Monosulfate was synthesized mixing C3A (tricalcium aluminate), gypsum (calcium sulfate), and water with an intercalation method. The product form the synthesis was characterized by FE-SEM, WDXRF, PXRD, and FT-IR. Experiments with different doses of monosulfate were carried out for kinetic. As a result of experiment, the concentration of As(V) was reduced from 0.67 mM to 0.19 mM (0.67mM of monosulfate) and 0.178 mM (1.34 mM of monosulfate). The concentration of sulfate was increased with As(V) decrease. The result of PXRD showed that the d-spacing of inter layer (d003 peak) was shifted from 8.927 Å to 8.095 Å because the sulfate in the inter layer of monosulfate was exchanged arsenate with water molecules bonded. From the FT-IR results, a new single band (800 cm-1)was observed after the reaction of monosulfate and As(V). The arsenic removal can be regarded as anion exchange mechanism that is one of the characteristics of LDHs from the results of PXRD and FT-IR analysis.