Evaluation and Optimization of chromium removal from synthetic aqueous solutions by powdered green algae Spirogyra

Heavy metals are the main pollutants in nature. Chromium is a heavy metal which is widely used. Hexavalent chromium solubility and mobility in aqueous solutions is so high and it is easily reduced. Biosorption is a process in which heavy metals are uptake through passive binding by nonliving biomass from aqueous solutions. The present study aimed to determine the capability of powdered Spirogyra to remove chromium from synthetic aqueous solutions under the influence of process parameters includes pH, algal dosage, and metal initial concentration. This study was empirically carried out in laboratory scale through a batch system in Kashan region, Iran, in September 2014. Hexavalent chromium stock solution (500mg/l) was made by solving 1.417g of dichromate potassium in 1 liter of distilled water. The experiments were conducted with initial concentration of 10, 25, and 40mg/l of hexavalent chromium in pH levels equal to 3, 7 and 11 and algal dosages of 0.2, 0.5 and 1g/l. The repeated-measure test was applied for statistical analysis using SPSS 16 software. Maximum value of chromium removal was observed at pH=3 (70%). Hexavalent chromium removal value increased with increasing algal dosage from 0.2g/l (45%) to 1g/l (70%) in 100ml samples with 40mg/l concentration of Cr(VI). The amount of Cr(VI) bound by unit weight of biomass were increased from the initial concentration of 10 to 40mg/l about 27mg/g in all levels of pH. Low dosages of powdered Spirogyra can remove hexavalent chromium from wastewater and aqueous solutions.