Enhanced Reduction of Chromate and PCE by Pelletized Surfactant-Modified Zeolite/Zerovalent Iron

Abstract

The current research focuses on enhanced removal of chromate and perchloroethylene from contaminated water by a combination of a reduction material (represented by zerovalent iron, ZVI) and a sorption material (represented by surfactant-modified zeolite, SMZ). Natural zeolite and ZVI were homogenized and pelletized to maintain favorable hydraulic properties while minimizing material segregation due to bulk density differences. The zeolite/ZVI pellets were modified with the cationic surfactant hexadecyltrimethylammonium bromide to increase contaminant sorption and, thus, the contaminant concentration on the solid surface. Results of chromate sorption/reduction indicate that the chromate sorption capacity of pelletized SMZ/ZVI is at least 1 order of magnitude higher than that of zeolite/ ZVI pellets. Compared to SMZ pellets, the chromate removal capacity of SMZ/ZVI pellets in a 24-h period is about 80% higher, due to the combined effects of sorption by SMZ and reduction by ZVI. The chromate and PCE degradation rates with and without surfactant modification were determined separately. The pseudo-first-order reduction constant increased by a factor of 3 for PCE and by a factor of 9 for chromate following surfactant modification. The enhanced contaminant reduction capacity of SMZ/ZVI pellets may lead to a decrease in the amount of material required to achieve a given level of contaminant removal.

Mineralization of 2,4,6-Trinitrotoleune (TNT) in Coastal Waters and Sediments

“…In the field, Fenton's reagent (Fe 2+ /H 2 O 2 ) has been used in recent years to remove or transform a variety of pollutants, including TNT, found in groundwater or wastewater treatment streams Stenstrom 2002, Oh et al 2003). Li et al (1999) found that Fenton's reagent was more effective at pH 6 than pH 3 due to the precipitation of Fe 3+ at pH >5. Because marine ecosystems have a pH near 8, Fenton chemistry may mediate some component of TNT degradation through active photochemical redox cycling of iron (Miller et al 1995), an important component of which is H 2 O 2 generation.…”

Hexavalent Chromium Reduction with Zero-Valent Iron (ZVI) in Aquatic Systems

“…Enhanced removal of Cr(VI) from contaminated water was also achieved using a combination of ZVI and sorbents such as zeolite/ZVI pellets, prepared by mixing ZVI and zeolite at a mass ratio 73:20 on a rotating dish with a binder (7% of the total weight, made of 1:1 by weight of sodium silicate and sodium aluminate in liquid form), washed with CaCl 2 solution and dried in an oven at 177°C (Li et al 1999. Another laboratory method was suggested by Dos Santos Coelho et al (2008) who used for Cr(VI) reduction ZVI/Fe 3 O 4 composites prepared by manually grinding a dry mixture of ZVI and magnetite powders using a mortar and pestle (mechanical alloying).…”

Removal of chromium(VI) and uranium(VI) from aqueous solutions by the immobilized nanoscale Fe0

“…В якості останньої можуть виступати природні глинисті мінерали, ха-рактерним для яких є здатність до утворення міцних поверхневих комплексів з іонами металів за рахунок значної кількості активних центрів, які можуть зна-ходитись як на базальних, так і на бічних гранях крис-талів [8]. Крім природних мінералів в якості стабілі-заторів нанодисперсного заліза також застосовують алюмосилікати, модифіковані різними органічними речовинами [9,10].…”