Abstract
The removal of BTEX (benzene, toluene, ethyl-benzene and p-xylene) from contaminated groundwater was evaluated by paper mill sludge-based activated carbon, prepared by chemical activation and pyrolysis.The effects of pH, time, adsorbent dosage and adsorbate concentration were studied through batch adsorption experiments. Selected physical and chemical characteristics of the adsorbents, such as specific surface area (613m2/g), pore volume distribution (micropore: 277cm3/g, mesopore: 365cm3/g) and surface functional groups (carboxylic, alkyl and aliphatic groups) were determined by N2 adsorption-desorption diagram and FTIR, respectively. The removal efficiency of the four target compounds would be more than 92 %, which the initial concentrations of BTEX and the adsorbent dosage were 40 mg/l and 1000 mg/l, respectively. It was proved that pH and ionic strength have insignificant effects on the adsorption efficiency. The order of adsorption amount in all experiments was > ethyl-benzene > toluene > benzene. The kinetic data proved a closer fit to the pseudo-first-order model. The isotherm experimental data showed a better fit to either Freundlich or Langmuir model. In addition, a series of experiments was conducted to evaluate the capacity of the adsorbent in adsorbing the BTEX from a groundwater sample contaminated with gasoline.
Highlights
Nowadays, production and storage of gasoline are increasing, leading to the widespread release of mono aromatic hydrocarbons including benzene, toluene, ethyl-benzene and xylenes (BTEX) into soil and groundwater
The batch adsorption experiments were carried out to determine the effect of parameters such as pH (3,5,7,9,11), contact time (0.5, 1, 1.5, 2, 2.5 hr), adsorbate concentration (10, 20, 30, 40 mg/l), and salt effect (124, 300, 700 mg/l of calcium chloride) on the removal of BTEX from groundwater solutions by activated carbon prepared from paper mill sludge
Porous Characterization of the Adsorbents The most common method to analyze porous structure of an adsorbent is employing N2 adsorption-desorption isotherm data in 77K which is shown in Fig. 1. ]
Summary
Production and storage of gasoline are increasing, leading to the widespread release of mono aromatic hydrocarbons including benzene, toluene, ethyl-benzene and xylenes (BTEX) into soil and groundwater. Gasoline leakage from underground storage tanks and transfer pipes are the main sources of soil and groundwater contamination with BTEX [2]. These compounds have been associated with long-term negative health effects. Air stripping is effective method for BTEX removal in aqueous solutions. Capability of novel adsorbents such as carbon nanotubes and their surface modified forms to remove BTEX from aqueous solutions were investigated [8]; high production cost has been mentioned as the main drawback. The adsorption capacity of the adsorbent for BTEX was investigated by determining the equilibrium isotherms
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