Bioremediation potential of microalgae for copper ion from wastewater and its impact on growth and biochemical contents: equilibrium isotherm studies

The use of microalgae to remediate heavy metal-contaminated wastewater has attracted more and more interest. In this investigation, the green microalgae Chloroidium ellipsoideum and Desmodesmus subspicatus were used to study copper uptake from nutrient media and its effect on algal growth and metabolism. The growth of C. ellipsoideum and D. subspicatus generally decreased with increasing copper concentrations. There was a decrease in the carbohydrate content of C. ellipsoideum , but an increase was observed in D. subspicatus by treatment with various copper concentrations. Low concentrations of copper helped to increase the protein content of C. ellipsoideum , but a decline in protein content was reported for D. subspicatus . By increasing the copper concentrations, an increase in the free amino acids and a decrease in the total lipid content of C. ellipsoideum and D. subspicatus were recorded. At 0.1 mgl ^–1 copper concentration, pH of 6.8, and algal dose of 1 g L ^−1 , the maximum biosorption capacity of C. ellipsoideum was 0.398 mg g ^−1 , corresponding to the maximum reduction of 68.66% of Cu ^2+ , and 0.396 mg/g for D. subspicatus , corresponding to the maximum reduction of 59.52%. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were applied to describe the isothermal biosorption of Cu ^2+ ions in studied algae. The Dubinin–Radushkevich model indicated that the copper biosorption mechanism was physical in nature. Cu ^2+ has a greater affinity for D. subspicatus than C. ellipsoideum , suggesting that C. ellipsoideum was relatively more resistant to Cu ^2+ toxicity than D. subspicatus . Moreover, FT-IR analysis revealed that carboxyl, amide, amino, carbonyl, hydroxyl, methyl and alkyl groups were the key groups responsible for the biosorption process. Therefore, D. subspicatus and C. ellipsoideum are efficient biosorbents for Cu ^2+ and can be used as biosorbents for heavy metals removal from wastewater.