Effect of activating agents on the adsorption of ammoniacal nitrogen using activated carbon papaya peel

Abstract

Ammoniacal nitrogen is one of the harmful pollutants in the waste water. High level of this pollutant can give a negative impact towards environment especially to aquatic life. Activated carbon has been known as an excellent adsorbent and widely used due to its large adsorption capacity. Papaya peel, a fruit waste, is a potential environmental friendly adsorbent. In this study, the efficiency of activated carbons from papaya peel to adsorb ammoniacal nitrogen by using different activating agents is investigated. The activated agents used are nitric acid (HNO3), phosphoric acid (H3PO4), acetic acid (C2H4O2), sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium chloride (CaCl2). The purpose of chemical activating agents is to enhance the adsorption capacity and its removal efficiency. Maximum adsorption capacity (qm) for ammoniacal nitrogen were determined by calculating the concentration of ammonium ion by using Nessler method (spectrophotometer, DR6000 Hach, US). The highest ammonium adsorbed was obtained from papaya peel activated with potassium hydroxide (KOH) with maximum adsorption capacity of 2.885 mg/g mass adsorbent used. The surface characterisation for the raw, after activation with potassium hydroxide and after adsorption was analysed by using Field Emission Scanning Electron Microscopy (FESEM) and the element analysis was conducted by using Energy-dispersive X-ray spectroscopy (EDX). FESEM morphology revealed that the activated carbons were found to be mainly micropores and mesopores. EDX revealed that nitrogen was the major component adsorbed by the activated carbon and it can be concluded that ammoniacal nitrogen has been adsorbed by the adsorbent. This result shows that papaya peel activated with KOH can effectively be used to remove ammoniacal nitrogen from the aqueous solution.