Abstract

Adsorption of chromium (III) on a smectite from a tanning wastewater was studied. Similarly adsorptions of sodium, chloride and sulphate were analyzed. Tests were carried out with solutions with a chromium (III) content ranging between 0.62-31.20 mmole/l. The method used to develop this work covered the characterization of the solution and of the smectite before and after each test. Solutions were characterized by chemical analyses and by visible spectrophotometry. The original smectite and smectites after each adsorption test were characterized by chemical analyses, by X-ray diffraction, by scanning electron microscopy and by surface chemical analysis via an electron microprobe. The results allowed us to determine the principal physicochemical characteristics of the chromium (III) adsorption on smectite. Monomeric chromium (III) was detected in the tanning wastewater and in each of the solutions prepared from the original solution. Adsorptions of sodium, chloride and sulphate were negligible for tests performed with low concentration solutions. Such behaviour changed with the increase of the prepared solution concentrations. The maximum adsorptions determined were: 0.81 mmole of chromium (III)/g of smectite; 0.30 mmole of sodium/g of smectite; 0.30 mmole of chloride/g of smectite and 0.15 mmole of sulphate/g of smectite. Finally, the Langmuir equation was used in order to quantify the chromium (III) adsorption.