Enhanced methylene blue removal from aqueous solution using modified rubber seed (Hevea brasiliensis)

Abstract

Nowadays, dyes have been considered as common industrial pollutants that are harmful to the environment. In order to address this problem, this study investigated the potential use of natural rubber (Hevea brasiliensis) seeds (NRS) to remove methylene blue (MB) from aqueous solution. NRS was pretreated using epichlorohydrin (ECH) and concentrated H2 SO4 in various impregna-tion ratios to produce modified NRS called NRSEA. The structural and surface properties of the adsorbent were characterized using Fourier transform infrared and scanning electron microscope. The effects of different system variables (pH, initial MB concentration, contact time and adsorbent dosages) and the presence of ion intruders on adsorption capacity were studied. The results of MB adsorption ability test onto NRSEA showed that the adsorption capacity increased with increasing pH (within the pH range of 7–12) and decreased afterwards, the optimum initial MB concentration reached at 800 mg/L, and the equilibrium state was achieved at 120 min of contact time. Moreover, NRSEA was identified as having a higher adsorption affinity towards MB molecules than NRS. The isotherm data obtained from isotherm studies were fitted well to the Langmuir isotherm with a maximum adsorption capacity of 784.31 mg/g and best described by pseudo-second-order kinetic model. The thermodynamic test results exhibited that the adsorption process was endothermic and spontaneous at 45°C and 65°C.