Synthesis and characterization of surface modified banana trunk as absorbent for benzene removal from aqueous solution

Abstract

Petroleum monoaromatics especially benzene contamination in water and wastewater is the major concern in the industry today. Various removal techniques have been studied. The adsorptive removal process is considered as one of the most cost-efficient and feasible methods because it does not require a large amount of energy and additional chemical. In adsorption technology, several problems such as adsorbent cost, adsorption selectivity and adsorbent reusability are the main concerns. Therefore, the potential conversion and modification of agrowaste adsorbent into an effective adsorbent alternative to removing benzene constituent from the wastewater were studied. The banana trunk (BT) was selected as an agrowaste model in the present study. The raw BT (Raw-BT) was first mercerized and this mercerized BT (M-BT) was then reacted with different surfactants, namely cetyltrimethylammonium bromide, CTAB (M-CTAB-BT), 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol, Triton X-100 (M-TX100-BT) and sodium dodecyl sulfate, SDS (M-SDS-BT). Surface etherification was also conducted by using 3-chloro-2-hydroxypropyl trimethylammonium chloride, CTA with the mass ratio of 1 and this etherified BT (M-1CTA-BT) was then coated with SDS (M-1CTA-SDS-BT). All the adsorbents were characterized by using a Fourier transform infrared spectrometer, a field emission scanning electron microscope, an x-ray photoelectron spectroscopy analyzer and nitrogen adsorption/desorption analysis. The experimental batch adsorption studies showed that the adsorption capacity increased in the following order: Raw-BT < M-BT < M-CTAB-BT < M-TX100-BT < M-1CTA-SDS-BT. The Langmuir maximum benzene adsorption capacity, qL,max achieved by the M-1CTA-SDS-BT was 468.187 × 10-3 mmol/g. The fundamental adsorption equilibrium and kinetic studies revealed that the benzene adsorption data were fitted well into the Langmuir isotherm and pseudo-second order kinetic models which suggested that the adsorption process was governed by a physical phenomenon. The film diffusion was considered as the rate-limiting step for the overall benzene adsorption process. The adsorbents were chemically stable within the pH range. It was revealed the benzene adsorption was an endothermic and non-spontaneous process. The regeneration study using 50 % ethanol-water as the desorbing agent, demonstrated that the modified adsorbents could withstand five adsorption/desorption cycles without a drastic reduction of adsorption uptake (8.5 - 13.0 %). The BT could potentially be employed as an adsorbent precursor for benzene adsorptive removal from aqueous solution.