Calcium ion adsorption of Leucaena leucocephala wood biochar activated with coconut vinegar

A positive correlation has been reported recently among the number of Chronic Kidney Disease of Unknown Etiology (CKDu) patients and the levels of groundwater hardness. Hence, the need for a low cost and a simple domestic process to reduce the hardness of potable water is identified to improve living standards of low-income communities in these disease affected areas. Biochar has emerged as a low cost adsorbent for water treatment, because of its abundance and cost-effectiveness. This study was aimed to evaluate the ability of natural coconut vinegar, in activating Leucaena leucocephala wood biochar to be used in calcium ion (Ca²⁺) removal from potable water. Column tests showed a 1.7 fold increase of Ca²⁺ adsorption capacity and a 7 fold increase of Ca²⁺ retaining capacity upon the vinegar treatment. Batch studies matched with both Langmuir (R² = 0.9761) and Freundlich (R² = 0.9785) isotherm models. Ca²⁺ amount in solutions were measured using flame photometry. Ca²⁺ adsorption capacities of raw biochar and activated biochar determined by column tests ranged from 3.10-3.82 mg/g and 5.27-6.68 mg/g respectively while Ca²⁺ retaining capacities ranged from 0.16-0.22 mg/g and 1.28-1.4 mg/g respectively. Fourier transform infrared spectra, suggests hydration of the C-O-C bridges of the biochar surface introducing new -O-H groups and possible introduction of carbonyl/ ester/carboxylic functional groups to the biochar surface upon vinegar treatment. According to scanning electron microscopy porosity of the biochar remained stable after the vinegar treatment.