Water Clarification and Selected Heavy Metal Biosorption by Maerua decumbens Root Tuber Powder

Abstract

The increasing population affects the use of fresh water resources thus creating a need for water purification. Most of the commercial techniques are high cost and thus a need for a low cost water clarifying and purification method. This research considered Maerua decumbens root tuber powder as a biosorbent and a natural coagulant .The aim was to analyze Maerua decumbens root tuber powder efficiency, as a primary coagulant, to determine the parameters (physical and chemical) reduction in clarified water, and optimization of various sorption parameters by biosorption of Cu (II), Cr (III), Cd (II), and Pb (II). Maerua decumbens plants was collected from Baringo County in Kenya, The root tubers were washed cut into small pieces dried and ground into powder. Water analysis parameters determined included: alkalinity, conductivity and turbidity. The optimum dosage for the root tuber was established at 1.25 mg/L. The root tuber used reduced the alkalinity, conductivity and turbidity to permissible levels. The effect of varying pH on Maerua decumbens and Alum was also compared and the tuber compared well to Alum. In biosorption studies, the optimum pH was 5.0 for Cu (II), 5.2 for Cr (III) and Cd (II); 5.5 for Pb (II).Contact time was established after 40 min for Pb (II) and 30 min for Cr (III), Cd (II), and Cu (II). FTIR analysis for Maerua decumbens root tuber powder indicated the presence of carbonyl, carboxyl, hydroxyl and amino functional groups, which were responsible for biosorption of Cr (III), Cd (II), Cu (II), and Pb (II).The data for biosorption fitted well in pseudo second-order kinetic model than first order. The isotherms model for the biosorbent fitted well with the Freundlich isotherm model than with the Langmuir isotherm model. The study showed that this natural coagulant was a good biosorbent and exhibited good coagulation activity for the removal of Cr (III), Cd (II), Cu (II), and Pb (II) from aqueous solution.