Remediation of NAPL-Contaminated Brackish Water by Synthesized Organoclay: Experimental Analysis and BNN Predictive Model

Abstract

This study aimed at synthesizing organoclay to remove benzene, toluene, ethylbenzene, and xylene (BTEX) and phenol as nonaqueous phase liquid (NAPL) from brackish water. The cetyltrimethylammonium bromide (CTAB) was used to synthesize organoclay owing to its high hydrophobicity and capability to adsorb aromatic and phenolic compounds with varying cation exchange capacities (CECs). The effects of contact time, concentration of BTEX and phenol as dense nonaqueous phase liquids (DNAPL) and light nonaqueous phase liquids (LNAPL), and organoclay CECs on the removal of contaminants were studied. The adsorption capacity of the synthesized organoclay was determined. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) tests were conducted to investigate the characteristics of the synthesized organoclay. A Bayesian neural network (BNN) was developed to predict the experimental adsorption capacity accounting for uncertainties. The structure and postadsorption changes in the organoclay bonds were probed via FTIR tests. The results indicate that BTEX and phenol removal efficiencies were 95.6% and 68%–84%, respectively. The measured adsorption capacity for benzene, toluene, ethylbenzene, and xylene were 4.7, 6.2, 9.2, and 7.8 g/g, respectively, relative to the initial weight of the sorbent. The developed BNN model can accurately predict the adsorption capacity of organoclay. A sensitivity analysis was performed based on optimized BNN model to examine the influence of each parameter on the adsorption capacity, which confirmed laboratory results and revealed that the optimal values of CECs are approximately 150%–200%. Given the high removal capacity and ease of synthesis, it was concluded that the synthesized organoclay could be an efficient and competitive alternative to existing removal systems.