Peanut Husks Functionalized with Citric Acid and Ethylene -1, 2-Diamine for Removal of Lead (Ii) Ions from Contaminated Water
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Consumption of water contaminated with heavy metals poses a major risk. Consequently, safe and effective treatment of contaminated water remains a topic of global concern. Lead is among the most prevalent heavy metal contaminants as it is widely used in metallic form. It is easily absorbed by the body through water intake. In body, lead inhibits the enzymes and induces generation of reactive oxygen species that intensifies oxidative stress. This mechanism makes lead neurotoxic, mutagenic, teratogenic and carcinogenic. Studies reveal that some parts of Tanzania have higher levels of lead than the recommended level by World Health Organization and East African Community of 0.01mg/L in drinking water. Although several water treatment methods are available, adsorption offers an attractive method for the removal of heavy metal in terms of cost of adsorbent production, simplicity of design and operation. Cellulose-carboxylate ion and 6-(2-aminoethylamino)-6-deoxycellulose (or called celen) are thermally stable and can be easily employed for the adsorption of cations from aqueous medium. Hence, this study was aimed at modifying the peanut husks with citric acid and ethylene-1,2-diamine to synthesize cellulose-carboxylate ion and celen respectively to determine the adsorption capacity and efficiency in the removal of Pb(II) ion from contaminated water. Peanut husks were collected from Dodoma region in Tanzania, washed, ground and modified with citric acid and ethylene-1,2- diamine to prepare adsorbents. FTIR confirmed the peanut husks to contain cellulose and that the citric acid and ethylene-1,2-diamine are anchored onto the cellulose. XRF revealed that the peanut husks contained zero percent of Pb metal and XRD proved the amorphous nature of the cellulose present in peanut husks. Batch experiments were carried out to determine the effect of pH, contact time, temperature, initial concentration and adsorbent dose on adsorption process. The experimental data were fitted in Langmuir and Freundlich isotherms and were found to fit best in Langmuir isotherm as it had the highest value of correlation coefficient of 0.998, 0.959 and 0.997 for UMP, CMP and EMP respectively. The maximum monolayer adsorption capacities were 18.8 mg/g for UMP, 11.36mg/g for CMP and 19.23mg/g for EMP. Based on the adsorption capacities, EMP is a better adsorbent than the rest. These results indicate that peanut husks tethered with citric acid and ethylene-1,2-diamine constitute a promising material for the development of an adsorption technology for the removal of Pb(II) ion from aqueous systems.