Abstract
Natural as well as acid modified dead biomass of brown marine alga Sargassum sp. was employed for the elimination of cadmium and zinc ions from synthetic wastewater; batch mode experiments were carried out to optimize various factors like adsorbent dosage, contact time, pH, agitation speed and primary metal ions concentration at room temperature (298.15 K) for both types of adsorbents i.e. natural and acid treated. Application of Langmuir and Freundlich isotherms suggested that the modified biomass adsorbed better as compared to the natural one; though sorption on the natural biomass was a physical process while that on the modified one was a physico-chemical process and thus was relatively difficult. The quantity of cadmium ions adsorbed was greater than that of zinc ions. Adsorption equilibrium for the metal ions sorption on treated Sargassum sp. biomass was established within 60 min for both cadmium and zinc ions with 95.3 and 90.1% removal efficiencies, respectively, but it was greatly influenced by the pH of the solution. The optimal conditions in the batch experiments were as follows: cadmium ions were removed effectively using 0.5 g of adsorbent and 5 mg/L initial metal ions concentration at pH 4 and 150 rpm agitation speed whereas the best results for zinc ions were obtained with 1 g of adsorbent and 5 mg/L initial metal ions concentration at pH 3 and 200 rpm agitation speed. The experimental data fitted well to the pseudo first order model as the values of metal uptake capacities were in good agreement with the experimental values. Thermodynamic studies show that the process is spontaneous and endothermic in nature. Desorption and regeneration studies reveal that recovery of biosorbent is low.
Highlights
Provision of uncontaminated water to meet human needs has become a matter of great concern all over the world (Ramirez and Holmes 2008)
Adsorption equilibrium for the metal ions sorption on treated Sargassum sp. biomass was established within 60 min for both cadmium and zinc ions with 95.3 and 90.1% removal efficiencies, respectively, but it was greatly influenced by the pH of the solution
The optimal conditions in the batch experiments were as follows: cadmium ions were removed effectively using 0.5 g of adsorbent and 5 mg/L initial metal ions concentration at pH 4 and 150 rpm agitation speed whereas the best results for zinc ions were obtained with 1 g of adsorbent and 5 mg/L initial metal ions concentration at pH 3 and 200 rpm agitation speed
Summary
Provision of uncontaminated water to meet human needs has become a matter of great concern all over the world (Ramirez and Holmes 2008). The usual complex compositions of wastewaters lead to different decontaminating processes for heavy metals involving techniques like chemical precipitation, coagulation, evaporation, extraction, membrane separation, reverse. Appl Water Sci (2017) 7:3469–3481 osmosis, solvent extraction, ion exchange, biological and electrochemical techniques; but these processes either engage high cost or are ineffective for elimination of heavy metals from less concentrated solutions (Mamatha et al 2012). Applications of such conventional treatment procedures involve continuous consumption of chemicals which results in further environmental harms. Nanocomposites and bionanocomposites synthesized by sophisticated techniques and materials have been emerging as novel adsorbent materials for the removal of heavy metals from wastewater (Rais and Imran 2015; Rais et al 2017; Rais and Anam 2017a, b, c; Rais and Imran 2017a, b)
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