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In this paper, biosorption of lead from aqueous solution on chitosan and modified chitosan from crab shells was investigated. Batch experiments have been carried out to find the effect of various parameters such as pH, temperature, sorbent dosage, heavy metal concentration and contact time on the biosorption of lead using these prepared adsorbents. Response surface methodology (RSM) was employed to optimize the process parameters. Based on the central composite design, quadratic model was developed to correlate the process variables to the response. The most influential factor on each experimental design response was identified from the analysis of variance (ANOVA). The optimum conditions for the biosorption of lead were found to be as follows: pH:10, temperature: 55°C, sorbent dosage: 2 g, metal concentration: 50 mg/L and contact time: 150 min. At these optimized conditions the maximum removal of lead by the chitosan and modified chitosan were found to be 84.38% and 89.83% respectively. From the analysis, the model’s coefficient of determination (R2) of (0.84 and 0.87 respectively of chitosan and modified chitosan) and F-value of (14.01 and 17.25 respectively for chitosan and modified chitosan) obtained proved that the experimental design model is adequate and can be used to navigate the design space. The sorbents were characterized using Fourier Transform Infra-red (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) spectroscopy. Freundlich and Lineweaver-Burk isotherm model well expressed lead biosorption onto the studied sorbent. The metal biosorption onto the sorbents correlated well with pseudo-second-order kinetic model. |
