Removal of Cr (VI) and Cr (III) From Polluted Water and Soil Sown with Beet (Beta Vulgaris) or Celery (Apium Graveolens) after the Addition of Modified Zeolites

Abstract

Clinoptilolite, which was modified with hexadecyltrimethylammonium-bromide solution (HDTMA-Br) in a proportion of 1/8 w/v (Ζ1), was applied for the adsorption of chromate anions from aqueous solutions. Different initial concentrations of chromate anions from 0 to 145 ppm were added as K2Cr2O7 to 1 g of modified zeolite adsorbent. Zeolite (clinoptilolite, Z) was also used for comparison reasons. The kinetic analysis of both adsorbents (Z, Z1) was studied at 25°C. Equilibrium isotherms of chromate anions were studied for clinoptilolite and modified zeolite at 25, 40 and 60°C. According to the kinetic analysis, the chromate anions adsorption capacity reached at 1115.10 mg Cr (VI)/kg adsorbent for Z1 and 35.05 mg Cr (VI) kg for Z. According to isotherms, the adsorption of Cr (VI) on Z1 and Z did not increase with the increase of temperature indicating that the whole adsorption mechanism is controlled by chemisorption and not by physical adsorption. Modified zeolite and zeolite were tested to two different soils, i.e. a soil amendments. The modification of clinoptilolite with HDTMA-Br leads to the creation of positively charged surface sites of zeolite increasing the adsorption of Cr (VI) as chromate anions. Such adsorbents can be applied for the removal of heavy metals and dyes in an anionic form from wastewater and soil solutions where negative charged sites of clinoptilolite present low adsorption capacity.