Nitrate adsorption towards ultrasound-assisted modified oil palm frond: Characterization and performance investigation using response surface methodology

Abstract

Nitrate is known as one of the nutrients contributing towards eutrophication condition, when its concentration exceeds threshold. Adsorption of nitrate had been studied extensively, and lignocellulosic adsorbent has been favourable of many researchers. In Malaysia, oil palm biomass is a readily available lignocellulosic material in high volume, specifically oil palm frond (OPF). However, the potential of OPF for nitrate adsorption is still not vastly explored. Hence, this study aims to determine the structural properties of ultrasound-assisted modified OPF and to investigate the performance as an adsorbent for the adsorption of nitrate via response surface methodology (RSM). Batch adsorption experiment was carried out according to the parameters set by central composite design (CCD) under RSM via Design Expert software. A steady state nitrate recovery of 65.0 % and adsorption capacity of 1.65 mg/g were achieved at pH 7.0, initial concentration of 15 mg/L, adsorbent dosage of 5.5 g/L, contact time of 12 hours and temperature of 32.5℃ Meanwhile, optimization condition was conducted with at pH 5.12, initial concentration of 25.0 mg/L, adsorbent dosage of 1.0 g/L, and contact time of 5 hours at 25℃ resulted to an average of 65.28 % nitrate removal percentage and 16.25 mg/g of adsorption capacity. FESEM, BET and FTIR showed successful grafting of quaternary amine ions on ultrasound-assisted modified OPF. This shows that the modified OPF is a potential adsorbent for nitrate.