Preparation of manganese oxide coated coal fly ash adsorbent for the removal of lead and reuse for latent fingerprint detection

Abstract

Heavy metals are becoming a huge problem in the environment and lead is one of them. Lead is disposed into water systems from huge industries such as paint industry, mining, and electroplating. In this study, manganese oxide coated fly ash (MnO 2 -CFA) was synthesized and characterized. The BET surface area of CFA MnO 2 -CFA was 18.4196 m 2 /g, 3 times more than the raw CFA (5.9231 m 2 /g). Batch adsorption experiments indicated that the uptake of Pb 2+ fitted well in a Elovich kinetics model while the adsorption isotherm best fitted the Langmuir model with a maximum adsorption capacity of 141 mg/g at 40 °C and a pH of 7. Thermodynamic parameters obtained proved that the adsorption of Pb 2+ ions using the MnO 2 -CFA was endothermic and spontaneous. Furthermore, the adsorbent was highly selective towards Pb 2+ in the presence of Mn 2+ , Zn 2 , Ni 2+ and Cd 2+ . The Pb 2+ removal % from a real water sample spiked with 30 mg/L Pb 2+ was found to be 83.33%. The spent adsorbent was further applied in latent fingerprint detection which showed that Pb 2+ -MnO 2 -CFA produced clearer latent finger print (LFP) images compared to MnO 2 -CFA. LFP images were still clear 8 days after application of the spent adsorbent, proving that Pb 2+ -MnO 2 -CFA is a promising labelling agent. • Manganese oxide coated fly ash was synthesized by hydrothermal method. • MnO 2 -CFA surface area (18.4196 m 2 /g) was 3 times more than the raw CFA (5.9231 m 2 /g). • MnO 2 -CFA shows the maximum adsorption capacity of 60.61 mg g −1 (Pb 2+ ) at 50 °C. • Reuse application of Pb 2+ -MnO 2 -CFA spent adsorbent for LFP detection under day light condition.