Washing of Marine Coastal Sand in a Batch Reactor: Sorption and Desorption of BTEX

Abstract

This study addresses the issues related to decontamination of marine beach sand accidentally contaminated by petroleum products. Sorption and desorption of BTEX (i.e., benzene, toluene, ethylbenzene, and xylene) onto the sand from Uran Beach, located near the city of Mumbai, India, were studied, and isotherms were determined using the bottle point method to estimate sorption coefficients. Alternatively, QSARs (i.e., quantitative structure activity relationships) were developed and used to estimate the sorption coefficients. Experiments for kinetics of volatilization as well as for kinetics of sorption and desorption in the presence of volatilization were conducted in a fabricated laboratory batch reactor. A mathematical model describing the fate of volatile hydrophobic organic pollutants like BTEX (via sorption and desorption in presence of volatilization) in a batch sediment-washing reactor was proposed. The experimental kinetic data were compared with the values predicted using the proposed models for sorption and desorption, and the optimum values of overall mass transfer coefficients for sorption (K s a s ) and desorption (K d a d ) were estimated. This was achieved by minimization of errors while using the sorption coefficients (K p ) obtained from either laboratory isotherm studies or the QSARs developed in the present study. Independent experimental data were also collected and used for calibration of the model for volatilization, and the values of the overall mass transfer coefficient for volatilization (K g a g ) were estimated for BTEX. In these exercises of minimization of errors, comparable cumulative errors were obtained from the use of K p values derived from experimental isotherms and QSARs.

Nonlinear Sorption of Organic Contaminant during Two-Dimensional Transport in Saturated Sand

“…Barry et al (2002) reported that the Langmuir model is applicable to cases in which sorption is limited to a finite capacity that is being represented [42]. Many studies on the sorption of various dissolved organic compounds onto the soil have reported that the Freundlich and linear models are more suitable than the Langmuir model [43][44][45]. This is because all models are similar to the linear model at low concentrations [46].…”

Evidence for Very Tight Sequestration of BTEX Compounds in Manufactured Gas Plant Soils Based on Selective Supercritical Fluid Extraction and Soil/Water Partitioning

“…Soil and sediment concentrations of benzene and the related compounds toluene, ethylbenzene, and the xylenes (BTEX) are routinely determined by U.S. EPA Method 5035/5030, which uses water (or methanol) extraction followed by purge-andtrap analysis. Several investigators have demonstrated that environmental aging of hydrophobic organics can reduce their bioavailability and their rates of desorption into water (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Studies on aromatic hydrocarbons have focused on multi-ring PAHs since their water solubilities are much lower than BTEX compounds (7,8,10,11).…”