Bioremediation of potentially toxic metal and reactive dye-contaminated water by pristine and modified Chlorella vulgaris

This is the first study on the biosorption of Cu2+ and reactive yellow 145 (RY145) dye by citric acid (CA), NaOH, and heat-treated Chlorella vulgaris (Cv). Influence of contact time, initial adsorptive concentration, and biomass dosage on the biosorption process was explored. The biosorption kinetics and isotherm were comprehensively investigated as well. The Fourier transform infrared analysis proved the successful insertion of carbonyl groups on Cv surface by CA modification and the intensification of all Cv functional groups by heat treatment. CA modified Cv was the best biosorbent for RY145, 0.5 g/L removes 97% of 10 mg/L solution (pH(i) 2) in 40 min. The biosorption was favorable, occurred via the formation of a monolayer of RY145 on the homogenous surface of CA-modified Cv and followed the pseudo-second-order kinetics. On the other hand, heat-treated Cv was the best biosorbent for Cu2+, 0.5 g/L removes 92% of 10 mg/L solution (pH(i) 5) in 5 min. The biosorption of Cu2+ on heat-treated Cv was complex and involves more than one mechanism. The Langmuir theoretical monolayer saturation capacity of RY145 on CA-modified Cv was comparable to other biosorbents, while that of Cu2+ on heat-treated Cv was drastically superior.