Removal of Heavy Metals From Aqueous Solutions Using Cocopeat.

The presence of heavy metals in wastewater, which is common in industrial and urban areas including mining industries, poses a harmful effect to human health and the environment. There is a high possibility of contamination of both surface and groundwater due to the discharge of heavy metal contaminated wastewater. Removal of such heavy metals has been a research focus to design an efficient treatment system. Some recent technologies that address this problem are likely to be very expensive. Thus, an alternative low cost treatment system that uses abundant biosorbents found in the Philippines such as cocopeat and yet equally effective in removing heavy metals in wastewater could be developed. Here, we studied the adsorption capacity of cocopeat to remove copper (Cu²⁺), zinc (Zn²⁺) and lead (Pb²⁺) ions in aqueous systems through batch and column experiments at different pH conditions. Using data from batch experiments, appropriate kinetic (time dependency) and equilibrium (isotherm) models were fitted on the sorbed and liquid phase concentrations to determine adsorption parameters. Retardation factors were calculated from breakthrough curves using column experiments. The pseudo-second order model captured well the kinetic data indicating that chemisorption is the rate-limiting step in the adsorption process. An increase the initial rate of sorption was observed with increase in pH. Langmuir isotherm fitted well the equilibrium data showing a monolayer adsorption on the likely homogenous active sites of cocopeat. Coco peat was found to be very effective in adsorbing Pb²⁺ and Zn²⁺at around pH 4.0. Breakthrough curves showed high adsorption as pH increases with retardation factor ranging from 1.07 to 1.70. Based on the results, the cocopeat can be used as a substrate medium in reactors, filter bed system, or constructed wetlands in treating wastewater with high concentrations of heavy metals beyond standard limits.