Removal of Petroleum Aromatic Hydrocarbons by Surfactant‐modified Natural Zeolite: The Effect of Surfactant

Abstract

Monoaromatic hydrocarbons including benzene, toluene, ethylbenzene and xylene isomers (BTEX) are a very important category of water pollutants. These volatile compounds are very hazardous because of their fast migration in soil and water bodies and their acute and chronic toxicities when inhaled or ingested, especially benzene which is a known carcinogenic molecule. In this study, a natural zeolite (i. e., clinoptilolite-rich tuffs) was modified by two cationic surfactants (i. e., hexadecyltrimethyl ammonium chloride (HDTMA-Cl), and N-cetylpyridinium bromide (CPB)). The prepared adsorbents were then characterized, and their adsorptive capabilities for BTEX examined at different experimental conditions. The results of adsorption tests at 24 h revealed that the adsorption capacity of the modified zeolites improved by increasing the surfactant loading (i. e., less than the critical micelle concentration (CMC), to higher than the CMC), which caused an increase in sorption capacity from 60 to 70% for HDTMA-modified samples, and from 47 to 99% for CPB-modified zeolite. Adsorption kinetic tests showed the optimum contact time was 48 h with an average BTEX removal of 90 and 93% for HDTMA-modified and CPB-modified zeolite, respectively. Results showed that by increasing of pH from 3 to 11, the sorption capacity of the adsorbent decreased markedly from 97 to 75%. Analyzing the influence of temperature showed that the adsorption efficiency of adsorbents for benzene reduced from 93% at 208C to 10% at 48C. However, the influence of temperature on other compounds was not remarkable. Overall, CPB-modified zeolite exhibited higher selectivity toward BTEX compounds at optimum experimental conditions. Although commercial powder activated carbon (PAC) showed a higher capacity for all BTEX compounds and faster adsorption kinetics, the adsorption capacity of the CPB-modified zeolite at optimized conditions was competitive with PAC results.

Application of Mineral Sorbents for Removal of Petroleum Substances: A Review

“…Mineral and organo-mineral sorbents are proposed as the alternative to activated carbon or organic polymers. Most studies concern the sorption of BTEX as volatile petroleum derivatives representatives [80][81][82][83][84][85][86][87]. In these papers, different organic compounds have been used for mineral surface functionalization, and the influences of pH, adsorbent dosage and initial concentration on sorption efficiency have been considered, together with the equilibrium and kinetics of sorption.…”

Study of the Adsorption of Bright Green by a Natural Clay and Modified

“…The first approach: the surfactant molecules interact with clay through their non-polar (alkyl) groups; hence the positive head of the surfactants points toward the bulk of the solution. The second approach [26]: in this approach, the adsorption of the cationic surfactant onto the negatively charged surface of the adsorbent can be considered to be controlled by two steps; (1) the formation of surfactant monolayer through the ion exchange and electrostatic attraction and (2) the formation of surfactant bilayer via hydrophobic interactions [30][31][32]. As a matter of fact, firstly, the positive head of the surfactants are exchanged with the interlayer exchangeable cations within the clay, thereby forming a surfactant monolayer with outward pointing head groups.…”

Kinetic Study of the Adsorption of Natural Organic Matter From Aqueous Solution by Surfactant Modified Zeolite

“…Then the conical flasks were shaken by an incubator shaker (150 rpm; 20°C) for 24 hours (22,24). To prevent the possible intervention of the chloride anions in the modification of the zeolite, samples were washed several times with distilled water to remove the remaining chloride.…”

“…The surfactant modification of the zeolite makes a hydrophobic environmental conditions for the partitioning of the organic molecules with low polarity and high molecular weight (27). The critical micelle concentration of SDS is 1.8 mmol/L (22,24). In order to determine the effect of surfactant concentration on adsorption of NOM, three initial concentrations of SDS surfactant (0.5, 1.8 and 20 mmol/L) were selected which are in lesser, equal and higher concentrations than the CMC of the surfactant for modification.…”

“…Then the flasks were shaken in an incubator shaker (20°C, 150 rpm) for 24 hours. The solid was washed with distilled water repeatedly until no bromine (Br -) was detected by AgNO 3 solution, and then it was dried in an oven at 50°C for 24 hours (22,24). The zeolite modified with 0.5, 1.8 and 20 mmol/L of SDS solutions were named as SMZ1, SMZ2 and SMZ3, respectively.…”