Modelling and Optimization of Energy-Efficient Procedures for Removing Lead from Aqueous Solutions Using Activated Carbons Prepared from Waste Tyres and Bauhinia purpurea Leaves

The present study provides two naturally available sources for making adsorbents, waste tyres and Bauhinia purpurea leaves, for the removal of lead from effluents. Equilibrium isotherms, kinetic models and thermodynamic studies were applied to observe the suitability of these adsorbents. Response surface methodology was adopted to investigate the influence of different process variables in lead adsorption process using both the adsorbents. For all the process parameters, the square and linear model terms were having significant effect than interactive model terms of lead adsorption process for both the adsorbents. The interaction effects of the process variables of X1X2, X1X3, X2X3 and X2X4 were highly influenced by the percentage removal of lead by using activated carbons prepared from waste tyres. To study the interaction effects of the process variables of X1X2, X2X3 and X2X4 were highly influenced by the adsorption efficiency of lead by using activated carbons prepared from Bauhinia purpurea leaves. All the squared terms, X1, X2, X3 and X4 show a negative influence on the adsorption of lead on the two adsorbents. The interaction effect between process variables of X1X2 (p: 0.000, t: 9.243), X1X3 (p: 0.03, t: 2.36), X2X3 (p: 0.000, t: 4.75) and X2X4 (p: 0.02, t: 2.71), were found to be statistically significant and have positive effect on adsorption efficiency using ACWT as an adsorbent. The interaction effect between process variables of X1X2 (p: 0.000, t: 8.1049), X2X3 (t: 5.9657, p: 0.000) and X2X4 (t: 5.9657, p: 0.000) was found to be statistically significant and positive effect on adsorption efficiency of lead, whereas other interactions were insignificant and did not influence the adsorption efficiency of lead using activated carbons of Bauhinia purpurea leaves adsorbent. Based on the statistical approach, the experimental results were analysed by using ACWT and ACBPL adsorbents for the removal of lead and the optimum process conditions were as follows: pH: 4.98 and 4.77, Ci: 140.01 mg/L and 105.7 mg/L, w: 0.12 g and 0.123 g, T: 314.46 K and 305.31 K and maximum adsorption efficiency of 95.64% and 95.55%, respectively.