The novel usage of dead biomass of green algae of Schizomeris leibleinii for biosorption of copper(II) from aqueous solutions: Equilibrium, kinetics and thermodynamics

Copper ion Cu(II) as a toxic and carcinogenic component can be deposited in liver resulting in subsequent abdominal pain, respiratory problems, liver and kidney failure. According to US Environmental Protection Agency, the maximum Cu(II) should be below 1.3 mg/L in industrial effluents. Cu(II) must be removed from wastewaters before disposal. Dead green algae Schizomeris leibleinii, an abundant solid waste, was applied as a novel sorbent for Cu(II) removal from aqueous solutions. Experimental factors including initial pH, contact time, adsorbent dosage, initial copper concentration and temperature were studied. FTIR and FE-SEM/EDS analyses were performed before and after adsorption. The maximum adsorption capacity was 55.06 mg/g obtained at 700 mg/L in optimal condition of initial pH = 6, contact time = 60 min, 0.4 g adsorbent in 50 ml copper(II) solution and T = 25 degrees C. The maximum adsorption was obtained 96.71 % at initial concentration of 100 mg/L in a 3.5 h contact time. Three kinetic models of Morris-Weber, pseudo first-order and pseudo second-order were used and the pseudo second-order was the best fit with correlation coefficient of 1 compared to Morris-Weber and pseudo first-order models with correlation coefficients of 0.977 and 0.843, respectively. Freundlich and Langmuir isotherms were more precise for experimental data to describe the equilibrium of the adsorption. This proves the process is both physisorption and chemisorption. The thermodynamic analysis revealed the process of Cu(II) sorption on S. leibleinii was feasible, spontaneous and exothermic. Comparing the adsorption capacity of S. leibleinii to other adsorbents for Cu(II) removal shows this biosorption has potential for industrial applications.