Effects of Several Surfactants and High‐molecular‐weight Organic Compounds on Decomposition of Trichloroethylene With Zerovalent Iron Powder

Abstract

We investigated the effects of coexisting surfactants and high-molecular-weight organic compounds on the reductive dechlorination of trichloroethylene by zerovalent iron powder to determine whether these additives had utility as washing reagents for remediation of soil and groundwater pollution. During the dechlorination reaction, the amount of trichloroethylene decreased, and the formation of cis-1,2-dichloroethylene was observed. The decomposition of trichloroethylene was found to be first-order with respect to the trichloroethylene and zerovalent iron concentrations when the solution contained no additives. The rates of decomposition of trichloroethylene in the presence of the additives were lower than the rate in the absence of the additives: the rate constant was reduced by a factor of 0.7 for the cationic surfactant cetyltrimethylammonium bromide; by a factor of 0.5 for the anionic surfactants sodium n-dodecylbenzenesulfonate, sodium n-dodecylsulfate, and sodium n-dodecanesulfonate and for the high-molecular-weight organic compounds soluble starch, beta-cyclodextrin, and polyethyleneglycol 6000; and by a factor of 0.2 for sodium laurate and the nonionic surfactants Triton X-100, Tween 20, Tween 60, Brij 35, and Brij 58. Comparison of the concentrations of the nonionic surfactants with their critical micellar concentrations indicated that the rate-reducing effect of these additives was due to solubilization of trichloroethylene into the micellar phase. The adsorption of trichloroethylene onto the zerovalent iron surface was also affected by the presence of the additives. Thus, our results indicated that the changes in the decomposition rate of trichloroethylene were determined by several factors.

Influence of mixed-surfactant on reductive dechlorination of trichloroethylene by zero-valent iron

“…The mixed surfactant of DPC and Brij36 with a higher hydrophilic-lipophilic balance (HLB) decreased the TCE dechlorination rate, whereas other mixed surfactant systems did not affect the dechlorination. It appears that a high concentration of surfactant inhibited the adsorption between TCE and ZVI in the interface between the aqueous phase and the solid surface [15].…”

“…In the case of a cationic surfactant, the temporary electrostatic interaction between the electronegative chlorine group in the TCE and the cationic head group of the surfactant enhanced the adsorption and reduction of TCE on ZVI [12]. It was also reported that a non-toxic, nonionic surfactant decreased the TCE removal rate [15]. More recently, a study was carried out on the use of mixed surfactants to remove chlorinated organic compounds [14].…”

Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

“…Surfactants such as cetyl trimethylammonium bromide (CTAB) and sodium n-dodecylsulfate (SDS) had been used to provide bulk hindrance to counteract the electrical and dipolar attraction between nano particles while providing colloidal stability. 188 For the treatment of TCE in soil, anionic surfactants such as SDS and CTAB could be useful as they promoted the solvation of TCE to the aqueous phase as TCE was desorbed from soil. 189 As soil contains 29 charged groups such as NH4 + and OH2 + , these anionic surfactants could be desorbed from nZVI and attached to soil instead, especially at pH <8, leaving nZVI bare and unstable.…”