Activated carbon derived from peel waste of Citrus madurensis for removal of Pb (II) in aqueous solutions

Abstract

Among the techniques used in contaminant removal in water, adsorption by activated carbon (AC) has been identified as an efficient method. Therefore, this study aimed to investigate the effectiveness of utilizing Calamondin (Citrus madurensis) peel as aprecursor for producing AC that can be used to remove Pb (II) ions from aqueous solutions. First cleaned and dried peel waste powder sample of Calamondin (10.00 g) was carbonized at 400 °C for 120 minutes and activated chemically with dil. H3PO4 (0.01M, 100 mL). The prepared AC was characterized by SEM/EDAX, FT-IR, and proximate analysis. The effects of initial Pb (II) concentration (1 to 5 ppm), adsorbent dosage (0.01to 0.05 g,) and shaking time (20 to 120 min,) on Pb (II) adsorption onto AC were evaluated by varying the process parameters at room temperature (30±2 °C) and at pH= 7. The residual Pb (II) content in each sample after treatment with AC was determined by AAS. All experiments were duplicated and results were reported as mean±standard deviation. The proximate composition of AC was found to be 48.61% ash, 8.71% moisture, 11.65% volatile matter, and 31.03% fixed carbon content. The prominent bands of the IR spectrum of AC correspond to O–H, -CH, and C=O stretching vibrations. Compared to raw material, AC had a more porous structure with an average pore diameter of 2.0 μm. Based on the results, the highest removal percentage of Pb (II) (98%) was observed at the initial concentration of Pb (II) 5 ppm, the adsorbent dosage of 0.03 g, and the shaking time of 20 minutes. Further, the equilibrium adsorption data were analyzed by the Langmuir and the Freundlich isotherm models and the equilibrium data were best fitted with the Langmuir isotherm model with R2=0.91. The maximum adsorption capacity (q0) of the AC was 10.63 mg g-1 with a residual Pb(II) concentration ranging from 0.02 mg L-1 to 0.14 mg L-1. These findings suggest that the AC produced from Citrus madurensis is a cost-effective and eco-friendly solution for removing Pb (II) from wastewater.