Porous clay heterostructure for wastewater treatment : a development from bentonite clay in Thailand

Abstract

A wide variety of toxic metals and organic chemicals are discharged to the environment as industrial or laboratory wastes, causing serious water, air, and soil pollution. One of the interesting materials for using as the adsorbents to adsorb these pollutants in wastewater treatment is porous clay heterostructures (PCHs). These porous materials are obtained by the surfactant-directed assembly of mesostructured silica within clay layers. In the present work, the PCHs were synthesized within the galleries of Na-bentonite clay by the polymerization of tetraethoxysilane (TEOS) in cetyltrimethylammonium ion and dodecylamine templates. These PCHs were functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) and N,N-dimethyl- decylamine to obtain the MP-PCH and DM-PCH for utilizing as heavy metal and organic pollutant adsorbent, respectively. According to N2 adsorption-desorption data, the results show that PCH, MP-PCH and DM-PCH had surface areas of 549.7, 488.7 and 459.9 m2/g, average pore diameter in the supermicropore to small mesopore range of 3.16,3.28 and 3.31 nm and pore volume of 0.45, 0.48 and 0.56 cc/g, respectively. Moreover, these adsorbents were investigated the adsorption properties which concerned with their function as adsorbents for aqueous solution. The results show that the adsorption capacity of MP-PCH was 0.22, 0.24, 0.50,0.48 and 0.11 mmol/g for Cd, Cu, Mn, Ni and Pb, respectively and the adsorption capacity of DM-PCH was 3.6 and 1.4 mM/g for 4-chloroguiacal or 2,6-dinitrophenol, respectively. They point out the potential of these PCHs for utilizing as the heavy metal and organic pollutant adsorbents in wastewater treatment.