Studies On Application Of Modified Zeolite In Treating Wastewater

Zeolite, a kind of aqueous silicoaluminate mineral with frame structure and numerous connecting holes, possesses excellent properties such as ionexchange, high efficient preferential adsorption, catalysis etc. These properties make it possible to use zeolite in purification of wastewater.This paper deals with the method of modifying natural zeolite and application to waste water treatment. The results showed that zeolite modified by hexadecyltrimethyl-ammonium bromide(HTAB) has higher adsorptive ability. The structure and adsorption mechanism of zeolite were studied by analyses on scanning electron microscopy , differential thermal , X-ray spectroscopy , TG-DTA . The effect of adsorption conditions on adsorption capacity of zeolite modified by HTAB were studied. The experimental results showed that when temperature at 250C, pH of water controlled at 6, the dosage of modified zeolite was 25g/L, the efficiency for organo-zeolite to remove Cr2O72- from water was 98%. The saturated adsorption capacity of organo-zeolite to Cr2O72- in water was larger than that of unmodified zeolite and the adsorption isotherm was accorded with Langmuir and Freundlich isotherm equation. Adsorption mechanism of dichromate on organo-zeolite indicated that since HTAB was too large to enter into the internal portion of the zeolite, sorption of the HTAB only occurred on the zeolite's external exchange sites. Surface adsorption of organo-zeolite to Cr2O72- is the predominant. The mechanism of anion retention appears to be the formation of an HTAB-anion precipitate on the zeolite surface.The decolorization efficiency of an aqueous solution of methyl orange with organo-zeolite as an adsorbent was studied. Influencing factors and the mechanism of adsorption were investigated in detail. The experimental results showed that the sorption isotherm of organo-zeolite was non-linear, which was the result of methyl orange exterior adsorption into HTAB. The rate of adsorption of dye on the organo-zeolite was high. pH values of solution were the key effect on decolorization. The decoloriation rate will decrease with the increase of temperature. In experiment the efficiency of decolorization was up to 99%.