ADSORPTIVE BEHAVIOR OF LOW-COST MODIFIED NATURAL CLAY ADSORBENTS FOR ARSENATE REMOVAL FROM WATER

Abstract

Millions of people in more than 70 countries are at risk of developing arsenicosis and other
health issues due to consuming elevated arsenic contaminated water. The present study aimed to use natural
clays heated at high temperature and treated with ferrous and ferric solutions through a simple coating
technique enhanced by moderate temperature for arsenate uptake from water. BET, XRF, XRD and SEM
methods were applied for the adsorbent characterization. Adsorption experiments were conducted in a series
of batch systems in terms of contact time, solution pH, initial concentration and the presence of coexisting
anions. The results indicated that the adsorption kinetics was better described by the pseudo-second order rate
model for all adsorbents. All adsorbents exhibited higher arsenate uptake efficiency in the acidic condition.
Langmuir model provided the maximum arsenate adsorption capacity of 250µg/g, 429.74µg/g and
747.38µg/g for calcined clay (MC), ferric calcined clay (MC-FeIII) and ferrous calcined clay (MC-FeII),
respectively. Among added coexisting anions, phosphate (PO3-) significantly decreased the arsenate
adsorption capacity of all adsorbents. Overall, regarded to a wide availability of raw materials, simplicity of
the modification and improvement of arsenate adsorption capacity, modified natural clay adsorbents,
especially MC-FeII, could be considered to be effective and low-cost to remove arsenate from water.