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 andBauhinia purpurea leaves, for the removal of lead from effluents. Equilibrium isotherms, kinetic modelsand thermodynamic studies were applied to observe the suitability of these adsorbents. Responsesurface methodology was adopted to investigate the influence of different process variables in leadadsorption process using both the adsorbents. For all the process parameters, the square and linearmodel terms were having significant effect than interactive model terms of lead adsorption processfor both the adsorbents. The interaction effects of the process variables of X1X2, X1X3, X2X3 and X2X4were highly influenced by the percentage removal of lead by using activated carbons prepared fromwaste tyres. To study the interaction effects of the process variables of X1X2, X2X3 and X2X4 were highlyinfluenced by the adsorption efficiency of lead by using activated carbons prepared from Bauhiniapurpurea leaves. All the squared terms, X1, X2, X3 and X4 show a negative influence on the adsorptionof 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 bestatistically 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 onadsorption efficiency of lead, whereas other interactions were insignificant and did not influence theadsorption efficiency of lead using activated carbons of Bauhinia purpurea leaves adsorbent. Basedon the statistical approach, the experimental results were analysed by using ACWT and ACBPLadsorbents for the removal of lead and the optimum process conditions were as follows: pH: 4.98 and4.77, 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 maximumadsorption efficiency of 95.64% and 95.55%, respectively.