Determination of Effectiveness of Luffa Cylindrica as an Adsorbent in Removal of Heavy Metals From Wastewater

Abstract

This piece of work reports the sorption properties of Luffa Cylindrica that have not been exploited and carbon from luffa to remove copper and chromium ions from aqueous solution. The effect of contact time, adsorbate concentration, particle size, pH, biomaterial dosage and Temperature was investigated. Particle size A (<425) gave the best adsorption values. Increase in concentration of metal ions resulted in decrease in % adsorption of the adsorbate, while increased pH values led to increase in % adsorption for both copper and chromium ions. Increased biomaterial loading also led to increased adsorption for both copper and chromium ions. Desorption studies were done with 0.1M concentrations of H2SO4, HCl and EDTA. It was noted that for copper, H2SO4 was the best followed by HCl and finally EDTA. Chromium on the other hand was best desorbed by EDTA but H2SO4 was still better than HCl. Luffa-metal ion bond and EDTA-metal ion bond played a significant role in the desorption capability of EDTA. The regenerated biomaterial was then subjected to another set of adsorption experiments to study the effect of concentration of the metal ion on adsorption and for both copper and Chromium, EDTA treated biomaterial gave higher adsorption percentages. Luffa sponge was also carbonized and 0.5g, 0.75g and 1g portions of carbonized biomaterial was used to determine the effect of concentration of both Copper and Chromium ions on their adsorption onto the carbonized biomaterial. Carbonized biomaterial gave higher adsorption percentages than fresh Luffa.30ml portions of real effluent samples from KIRDI’S leather division was treated with 0.5g and 2g portions of fresh Luffa to determine its efficacy in removal of Chromium. 2g portions were able to remove over 92% of Chromium from the effluent. Two adsorption isotherms were tested and Langmuir gave the best fit for chromium and copper, copper giving R2 value of 0.9570 and Chromium R2 value of 0.9728. qmax value, the monolayer adsorption capacity for copper using fresh luffa was found to be 2.9753mg/g, and b the Langmuir constant was found to be 0.1933l/mg.qmax for Chromium was found to be 1.3466mg/g and b Langmuir constant was found to be 0.6639l/mg.This means Luffa Cylindrica has a higher affinity for copper than chromium. The experimental data from carbonized biomaterial was also fitted to Langmuir isotherm. The R2 value for copper was found to be 0.9826 and qmax value of 5.4288mg/g, 1.8 times that of fresh luffa. R2 value for chromium with carbonized Luffa was found to be 0.9144 with qmax value of 2.3479mg/g which again is almost twice as much as that of fresh Luffa. Freundlich Isotherm gave R2 value 0.8194 for copper which was not close to unity so the data didn’t adhere to the isotherm. Chromium however gave gave R2 value of 0.9501with KF value of 0.5768 and n value of 3.367 indicating good adsorption. This study demonstrates that Luffa Cylindrica could provide a cheaper alternative for removing heavy metals from waste water.