Biosorption of Cu(II) Ions by Water Hyacinth Leaf Powder: Process Performance, Kinetics, and Biosorption Isotherm

The water hyacinth leaf powder (WH) was used to adsorb Cu(II) from wastewater. The WH was modified through sulfuric acid (A-WH) and sodium hydroxide (B-WH) treatments. The biosorption was studied with various initial pH, initial Cu(II) concentrations, and biosorp-tion time. The results show that the biosorption capacities of the biosorbents increase with the initial Cu(II) concentration. The optimum pH for the biosorption was 7.5, 7.0, and 7.5 for the WH, A-WH, and B-WH, respectively. The SEM images of the raw and treated WH revealed that alkali treatment could remove lignin more than the acid treatment, leaving more macropores in the B-WH than in the A-WH. The acid and alkali treatments to the WH leaf increase the biosorption capacity of the WH for Cu (II). The pseudo-second-order kinetic model can represent the dynamic behavior of the biosorption better than the pseudo-first-order model. The Langmuir model is better than the Freundlich model for describing the biosorption isotherm. The maximum biosorption capacities of the biosorbents predicted by the Langmuir model were 14.92 mg g−1, 18.32 mg g−1, and 23.27 mg g−1 for WH, A-WH, and B-WH, respectively.