Optimization of analytical parameters in preconcentration and determination of toxic trace elements with biowastes

In this study, economic and environment friendly biomass-based activated carbon (AC) synthesis is aimed to be used in the the determination of toxic trace metals by preconcentration of ppb levels to ppm. For this purpose, agricultural waste such as pineapple leaf, apple pulp, banana bunch, orange pulp, olive seed, hazelnut shell, coconut shell, pomegranate shell, peanut shell, almond shell, walnut shell, banana and orange peel were chemically modified with reagents including H2SO4 and citric acid, and then activated carbon were synthesized by pyrolysis at high temperature. The adsorbents prepared were characterized by FTIR, SEM, EDX and BET methods. In the preconcentration step, the conditions such as working pH, mixing time and first volume were studied to optimize the analytical parameters. The synthesized adsorbents were used for preconcentration of toxic elements such as Cd, Pb, Ni, Cr and U at the ppb levels in natural waters, under optimized conditions. Accordingly, pH: 6 for the peanut and walnut shells modified with sulfuric acid, pH: 4 for the almond shell and pH: 3 for the banana peel were found as optimum values. Related with stirring time, 30 min. for the banana peel and 45 min. for the others was found for sulfuric acid - modified AC. The values for citric acid-modified adsorbents are pH: 4 for the almond and walnut shells, pH: 6 for the banana peel and pH 3 for the orange peel were obtained as the optimum conditions. Similarly, 45 min. for the almond and walnut shells and 60 min. for the banana peel and orange peel were found to be the optimum stirring time, and 150 mL as optimum first volume. The ICP-MS method was used to measure due to its capable the multiple elements at the same time. At the optimum conditions, the concentrations of Cd, Pb, Ni, Cr and U in the natural waters were found to be 0.05 - 0.70, 0.1 - 6.5, 0.3 - 19,