Application of modified Spirulina platensis and Chlorella vulgaris powder on the adsorption of heavy metals from aqueous solutions

One of the effective methods to remove heavy metals is the use of biosorbents. The aim of this study was to assess the adsorption rate of metal ions; cadmium, lead and copper in the aqueous solution with Spirulina platensis and Chlorella vulgaris algae biosorbent sulfuric acid-modified powder. The adsorption rate of metals cadmium, lead and copper via modified Spirulina platensis and Chlorella vulgaris adsorbents by varied adsorbent contents (0.5-5 g), different pH's (3-7), various contact time (5-120 min) and the concentrations of cadmium, lead and copper (5-100 mg L-1) was assessed. The removal percent of metal ions via Spirulina platensis and Chlorella vulgaris biosorbents were different. At optimum pH 5 for copper and optimum pH 6 for cadmium and lead, the equilibrium time 60 min and adsorbent dosage 5 g L-1, the removal percent of cadmium, lead and copper with Spirulina platensis adsorbent was 92.76%, 94.09% and 80.75% respectively and with Chlorella vulgaris adsorbent was 87.52%, 90.09% and 84.75% respectively, wherein lead removal percent via both modified biosorbents was higher in relation to cadmium and copper. Based on the results, metals adsorption followed the Longmuir and second-order kinetics equation models. The isotherm models showed that capacity of modified biosorbents was higher in lead adsorption. The thermodynamics parameters assessment indicated that the process of cadmium, lead and copper ions adsorption on modified biosorbents was endothermic, spontaneous and physico-chemical. Thus, considering the high adsorption efficiency, Spirulina platensis and Chlorella vulgaris can be safely used as an effective option for biosorption of heavy metals from the aqueous solutions.