Removal of Aqueous Chromium (III) Ions Using Jordanian Natural Zeolite Tuff in Batch and Fixed Bed Modes

The present study was undertaken to evaluate the capability of natural zeolite tuffto remove Cr(III) ions from aqueous solutions by physical chemical method under specified conditions. Investigationsinvolved shake- flasks experiments conductedusing 1.0-8.0 g/L doseof 355-500 μm zeolite particles in solution of 50 mg Cr(III)/L at initial pH of 4.0 and 22°Cas well as fixed-bedexperiments conducted using 4.8-14.4 cm bed height, 5.66-12.45 solution velocity, 50-100 mg/L initial metal concentration, size cuts in the range +355-850μmand initial pH of 4.0-5.5. The equilibrium adsorption capacity reached 19.6 mg/g and the data fitte d well both Langmuir and Redlich-Peterson isotherms. Break points up to 2.5 hours were obtained at 5% breakpoint using fixed-beds of zeolite at the lower metal concentration and solution velocity but higher pH and bed depth. Mechanism of removal appears to be ion exchange of Cr(OH)2+at pH≤ 6.0 and adsorption on zeolite surface of fine Cr(OH)3 precipitate at pH 6.0.