The removal of organic persistent contaminants in the environment is a challenge due to their hydrophobic nature. In this work, the removal of 2,4-DCP based on the adsorption and Fenton oxidation was reported, where organobentonite (OB)-supported zero-valent iron nanoparticles (nZVI) generated a hydrophobic environment to enhance adsorption, as well as to reduce the aggregation of nZVI. Adsorption efficiencies of 2,4-DCP by organobentonites which modified with hexadecyl dimethyl ammonium chloride (DK1), octadecyl dimethyl benzyl ammonium chloride (DK3) and aminocaproic acid (DK5), were found to be 27.8, 25.3, 1.0 and 1.0%, while the degradation efficiencies of 2,4-DCP using nZVI/DK1, nZVI/DK3, nZVI/DK5 and nZVI/B were 73.5, 46.1, 27.1 and 25.7%, respectively, Characterization of nZVI/DK1 by SEM, EDS and XRD revealed that nZVI effectively Supported the interlayer and did not change the layer structure of DK1, and no peaks of 2,4-DCP was observed by FTIR and GC MS due to degradation. The degradation of 2,4-DCP fitted well to the Langmuir-Hinshelwood model, and about 80.24% of chemical oxygen demand (COD) was removed using nZVI/DK1, suggesting that enhanced removal was attributed to the synergetic effect between adsorption by DK1 and Fenton oxidation by nZVI as the catalyst. The high number of recycling times proves that nZVI/DK1 could be a potential material to degrade halogenated organic pollutants.

目前,虽然有很多关于纳米零价铁(NZVI)通过吸附、还原和氧化作用去除各种污染物的报道,但关于如何联合这些方法来提高污染物的去除率仍然不是很清楚.本实验研究了联合有机膨润土DK1(十六烷基三甲基铵盐改性,d(001)＝2.2 nm)吸附、NZVI还原、类芬顿氧化作用来去除溶液中2,4-二氯苯酚(2,4-DCP)的方法.在反应前30分钟,有机膨润土DK1负载NZVI(NZVI/DK1)通过吸附还原作用去除溶液中2,4-DCP,2,4-DCP和COD的去除率分别为16.1％和7.8％,说明了吸附还原作用对2,4-DCP的去除效果是有限的.接着向溶液中滴加适量的H2O2,在5 min内2,4-DCP的去除率由16.1％提高到了99％以上,COD的去除率达到了64.1％,这可能是由于NZVI腐蚀形成铁的氧化物缓慢释放出Fe2+和Fe3,增强了芬顿反应对2,4-DCP和降解产物的氧化去除效果.通过SEM,EDS,UV-Vis和GC-MS等分析方法佐证了上面的结果.最后提出了联合吸附、还原和Fenton氧化去除2,4-DCP的机制.

Sixteen alkyl three methyl ammol/Lonium salt modified bentonite(DK1) was used for preparation of supported nano zero valent iron(n ZVI/DK1),combined with Fenton method for removal of 2,4-DCP in aqueous solution. The different influences such as the initial p H value,H2O2 concentration,n ZVI/DK1 dosage,2,4-DCP initial concentration on 2,4-DCP removal were observed. The results showed that the 2,4-DCP removal efficiency were 29. 0%,45. 7%,20. 2%,71. 1% by DK1,n ZVI/DK1,n ZVI/H2O2,n ZVI/DK1 /H2O2,respectively. And the hydrophobic clay support n ZVI enhanced the removal efficiency of 2,4-DCP. The p H value of solution,H2O2 concentration were in control of Fe0 activity in Fenton and catalysis,which significantly influenced the degradation of 2,4-DCP. At the condition of p H 3,H2O2 concentration 10 mmol·L- 1,n ZVI/DK1 dosage 0. 5 g·L- 1,2,4-DCP initial concentration 50 mg·L- 1,2,4-DCP removal efficiency reached 93. 4%. While the COD removal efficiency can reach as high as 78. 6%,it is further proved that n ZVI/DK1 has the function of adsorption and degradation in Fenton method.

Nanoscale zero-valent iron ( nZVI ) was used as catalyst for persulfate oxidation of 2,4-dichlorophenol (2,4-DCP) to understand the roles of nZVI in generation of sulfate radicals. The results obtained from SEM and EDS demonstrate that changes on the surfaces of the nZVI were observed due to the Fe2+leaching, adsorption of organic matter and oxidation. In addition, the effects of initial pH, nZVI dosage, initial concentrations of persulfate and 2,4-DCP, temperature on the degradation of 2,4-DCP were investigated. The results indicated that 2,4-DCP removal efficiency increased with decreasing pH. When the concentration of DCP, S2 O2-8 , nZVI were 30 mg·L-1, 12.5 mmol·L-1, 2.0 g·L-1, the removal efficiency of 2,4-DCP reached 92.1%. The degradation process of 2,4-DCP conformed to the pseudo first-order kinetics. It was proposed to be a surface-controlled process with activation energy of 91.48 kJ·mol-1 .

Nanoscale zero-valent iron (nZVI) has received attention for its potential applications in contaminated site remediation due to its reactivity. However, it is still unclear how nZVI acts as a catalyst to generate sulfate radicals in heterogeneous Fenton oxidation of 2,4-dichlorophenol (DCP). In this paper, various Fe materials such as Fe2+, nano-ZVI, and nano-Fe3O4 (nFe3O4) were used as heterogeneous catalysts, where the removals of DCP by Fe2+, nZVI, and nFe3O4 were 11.9%, 9.0%, and 5.5%, while the degradation of DCP in the presence of persulfate increased to 34.4%, 37.8%, and 5.8%, respectively. These data indicate nZVI can potentially generate sulfate radicals. UV, SEM, EDS and XRD demonstrated that changes on the surface of nZVI occurred owing to the Fe2+ leaching. It was further observed that DCP degradation increased when the dosage of nZVI and persulfate concentration also increased. However, it decreased when the initial pH and DCP concentration increased. More than 98% of DCP degradation was achieved within 180min under optimum conditions, but less than 40% of chemical oxygen demand (COD) was removed. The degradation of DCP follows the pseudo-first-order kinetics and it is a chemical control reaction with an activation energy of 91.5kJmol−1. Finally, a possible mechanism of DCP degradation using the nZVI/PS system was proposed.

In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe(2)(+) was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180 min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe(2+) leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed.