Adsorptive removal of direct black 22 dye using pumice and scoria from aqueous solution and wastewater

Abstract

A textile industry releases large amounts of dying chemicals, which create severe water pollution when discharged untreated. Most of these dyes, because of their carcinogenic and mutagenic properties, they threaten human health and aquatic life. Adsorptive-based experiment was employed to investigate direct black 22-dye removal capacity of pumice and scoria from aqueous solution and textile wastewater. Preliminary test were conducted to optimize parameters. Optimum parameters of pH 4 and 5, adsorbent dose of 1.6g and 2g, contact time 90 min and 120 minutes, agitation time 30 min at shaking speed of 200 rpm and room temperature (22±1) were used to investigate the adsorption capacity using pumice and scoria respectively. Results of the study revealed that 50 mg/L direct black 22 dye ion concentrations reduced to 2.45mg/L and 3.1mg/L from aqueous solutions using pumice and scoria respectively. When compared to Nitrate and Fluoride, Phosphate, sulfate and chloride anions were the dominant interfering anions to compete direct black 22-dye tested in synthetic sample. Chloride was the dominant anion (973mg/L) found in wastewater analyzed for the experiment. The equilibrium data best fit to Langmuir and Freundlich adsorption isotherm with a maximum adsorption capacity of 7.71mg/g and 8.1 mg/g with correlation coefficient R2 (0.995 and 0.9899) using pumice and scoria respectively. Direct black 22 dye uptake model well fitted with pseudo-second order with correlation coefficient R2 (0.988 and 0.993) using pumice and scoria respectively. The results of the study demonstrate that naturally available pumice and scoria can remove direct black 22 dyes from aqueous solution and it is better to remove the major interfering anions and mixture of cofactors with suitable pretreatment techniques for real or wastewater sample before adsorption to reduce the interfering ions competing with direct black 22 dye.