Removal of paraquat herbicide by cetyltrimethyl ammonium bromide modified pineapple leaves

Abstract

Paraquat herbicide is categorised under contaminants of emerging concern (CEC) that can cause serious environmental problem and toxic effects towards human and animals. Also, the decomposing of pineapple leaves by burning in the field could create environmental problems such as air pollution. Therefore, in the present study, the pineapple leaves powder (PLP) was utilised as a low-cost adsorbent to remove paraquat from aqueous solution. The adsorption of paraquat from aqueous solution by PLP and surfactant-modified PLP (SMPLP) was examined. A series of SMPLP was prepared by reacting PLP with different concentrations of cationic surfactant cetyltrimethyl ammonium bromide (CTAB) (0.5, 1.0, 2.5, and 4.0 mM). The PLP and SMPLP were characterised using Fourier transform infrared (FTIR) spectroscopy after the modification process with CTAB and after adsorption with paraquat. The results show no significant changes in the chemical structure of pineapple leaves after modification. The SMPLP exhibited higher adsorption affinity towards paraquat herbicide. The adsorption experiments of paraquat were carried out in a batch mode at room temperature. The effect of paraquat concentrations (2–20 mg/mL) on the adsorption capacity of PLP and SMPLP were investigated. The suitability of adsorbent was tested by fitting the adsorption data into Langmuir and Freundlich isotherm equilibrium models. The experimental adsorption data well fitted to Freundlich isotherm with multilayer adsorption capacity of 13.0 mg/g. The highest adsorption of paraquat was obtained by SMPLP treated with 2.5 mM CTAB while the lowest adsorption was obtained by PLP. As a conclusion, the utilisation of surfactant-modified pineapple leaves powder can become an alternative adsorbent for the removal of herbicide compound in aqueous solution.