BIOSORPTIVE REMOVAL OF HEAVY METALS USING SARGASSUM FILIPENDULA FROM WASTEWATER

Abstract

Environmental pollution particularly from heavy metals in the wastewater is the most severe worldwide problem. Heavy metals are major pollutants in marine, ground, industrial surface and even treated wastewater. Effluents from large number of industries like textile, leather, tannery, electroplating, wood processing, paint, photographic film production, petroleum refining, dyes and pigment, etc. contains significant amount of heavy metals in their wastewater. The heavy metals are non-biodegradable and persistent in nature which can accumulate in the food chain. They are toxic and carcinogenic which causes a serious threat to the human health. To avoid health hazards it is necessary to eradicate these toxic heavy metals from waste water before its dumping into wastewater stream. Several conventional methods are available for removal of heavy metals from wastewater such as chemical oxidation, electro dialysis, ion exchange, chemical precipitation, reverse osmosis, membrane separation etc. These methods are costly, require high energy input, associated with generation of toxic sludge, and less effective. Biosorption has emerged out as a better economical and effective alternative treatment methods. In general low concentrations of heavy metals are present in the wastewater which can be removed by biosorption. This makes biosorption an economical and favorable technology for heavy metal removal from wastewater. For this study brown marine algae Sargassum filipendula was used as biosorbent for Pb2+, Cd2+, and Ni2+ ions biosorption from aqueous solution. The biosorbent was characterized by FESEM-EDS, and FTIR analysis. Batch experimentation was carried out for single and dual metal ion systems to examine the effect of various process parameters like temperature, initial metal ions concentration, pH, biosorbent dosage and contact time on effective removal of Pb2+, Cd2+, and Ni2+ ions. Response surface methodology was used to optimize the biosorption process parameters. Simultaneous removal of dual metal ions (Pb2+ and Cd2+) were also examined. The optimum process parameters for Pb2+ ions biosorption were obtained as temperature (34.8 °C), pH (4.99), initial Pb2+ ions concentration (152.10 mg/L) and biosorbent dosage (0.49 g/L) with 96 % of Pb2+ ions removal were achieved. The optimum values of four process parameters for iv Cd2+ ions biosorption were obtained as pH (5.7), temperature (34.2 °C), initial Cd2+ ions concentration (50.8 mg/L), and biosorbent dosage (0.99 g/L) with 99.56 % removal of Cd2+ ions. The optimum values of four process parameters for Ni2+ ions biosorption were obtained as temperature (41.47 °C), pH (5.4), biosorbent dosage (1.97 g/L), and initial Ni2+ ions concentration (83.18 mg/L) with 68.45 % removal of Ni2+ ions. The experimental data of Pb2+, Cd2+, and Ni2+ ions biosorption were fitted to six isotherm models. Non-linear regression analysis was used to identify the best-fitted isotherm model on the basis of normalized standard deviation and correlation coefficients. The parameters of isotherm models was examined by MATLAB 2013. The maximum biosorption capacity of S. filipendula estimated for Pb2+, Cd2+, and Ni2+ ions using Langmuir model were obtained as 367.942, 103.5, and 34.3 mg/g, respectively. The best fitted isotherm models were found to be Fritz (for Pb2+) and Redlich-Peterson (for Cd2+ and Ni2+). The experimental data of Pb2+, Cd2+, and Ni2+ ions biosorption were fitted to six kinetic models to determine removal rate of solute, rate controlling step and the biosorption mechanism. The kinetic data of Pb2+, Cd2+, and Ni2+ ions followed Bangham, pseudo second order, and pseudo first order kinetic models, respectively. Thermodynamic parameters were also examined. The overall biosorption process of Pb2+, Cd2+, and Ni2+ ions was spontaneous, endothermic and feasible in nature. Desorption study was also carried out to examine the regeneration and reuse capacity of S. filipendula. Desorption study shows the better reusability of S. filipendula during four consecutive cycles of biosorption and desorption without any significant loss of their biosorption capacities. According to physiochemical properties of metal ions, the order of metal ions uptake on S. filipendula was found to be Pb2+ > Cd2+ > Ni2+. The experiments for simultaneous removal of Pb2+ and Cd2+ ions from dual metal ions system were carried out to study the competitive effect of metal ions. For dual metal ion system: (a) the concentration of Pb2+ ions was changed from 0 to 300 mg/L with 50 mg/L of Cd2+ ions concentration (b) the concentration of Cd2+ ions was changed from 0 to 300 mg/L with 50 mg/L of Pb2+ ions concentration. The six multicomponent isotherm models were fitted to experimental data of dual metal ions biosorption. The best fitted isotherm models for dual metal ions biosorption system was found to be extended Freundlich isotherm model. The effect of presence of Pb2+ and Cd2+ ions on each other was found to be antagonistic in nature which results in less removal of both the metal ions.