Nitrate (NO3-) removal from wastewater by adsorption using modified kaolin

Abstract

This study aims to determine the effect of the initial concentration and pH conditions of the nitrate solution on the removal of nitrate in water, which was carried out in batch. The raw material used is kaolin, which is firstly mashed and sieved with a size of 120 mesh, then activated by immersing it in a 0.5 M HCl solution for 24 hours, followed by modification of the surfactant by immersion in a 0.5 M cetyltrimethyllammonium bromide (CTABr) solution for 120 minutes, and accompanied by stirring using a magnetic stirrer at a speed of 150 rpm. Before being used as an adsorbent, kaolin CTABr-modified was analyzed using a scanning electron microscope (SEM) to determine the surface morphology of the material. Batch adsorption test was carried out by adding 1 gram of kaolin CTABr-modified to 100 mL of a solution containing nitrate with various concentrations of 10; 20; 30 mg/L and the pH of the solution is 5; 7; 8. The experiment was carried out for 180 minutes, where every 30 minutes the solution was sampled and analyzed for nitrate content using a spectrophotometer UV-Vis. The conclusion of this study is that kaolin CTABr-modified can be used as an adsorbent, where the SEM test results show that the surface morphology of kaolin CTABr-modified is denser and more compact than the prepared kaolin and kaolin HCl-activated. Based on the experimental results according to the Langmuir isotherm equation, the constant value was 0.78. The mechanism of nitrate removal includes ion exchange, hydrogen bonding, and intermolecular interactions. The maximum adsorption capacity was 0.72 mg/g, found under acidic conditions (pH 5) and with a contact time of 180 minutes.