Amphiphilic compounds enhance the dechlorination of pentachlorophenol with Ni/Fe bimetallic nanoparticlesby Cheng-han Lin, Yang-hsin Shih, John MacFarlane

Chemical Engineering Journal

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ch lic b bDepartment of Civil and Environmental Engineering, Massachusetts Institute of Technology, M.I.T. 48-412, 15 Vassar St., Cambridge, MA 02139, USA e remo nce PC val by N

Fe surfa om Ni/ netics, increased sorption of PCP onto Ni/Fe surfaces with CTAB was observed ithout CTAB. This is the result of the small particle size of Ni/Fe-CTAB and the

Environmental Protection Agency [1], European Union, and

Taiwan. Although PCP has been banned since 1984, it is still found in the environment. In Taiwan, there is a contaminated site in a former PCP production facility that was the result of improper storage and disposal practices. A rapid and innovative technology for tate this remediation. t iron (NZVI) have tral halog lene, poly l ethers ( [2–6]. For a reduction reaction to take place, the HOCs are ad onto these ZVIs first. Electrons are transferred from ZVI to th and then to the intermediate products formed [7–10]. Compared with iron alone, bimetallic particles have shown higher kinetics and efficiencies for degradation of many chlorinated compounds [11–17]. In iron based bimetallic systems, the catalytic metal (Cu,

Pd, Pt, or Ni) stimulated the formation of atomic hydrogen or hydride on the surface, and changed the electronic properties of iron, which plays the role of electron donor and reductant for water ⇑ Corresponding author. Tel.: +886 2 33669442; fax: +886 2 33669443.

E-mail address: yhs@ntu.edu.tw (Y.-h. Shih).

Chemical Engineering Journal 262 (2015) 59–67

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Chemical Engine w.Pentachlorophenol (PCP) with a pKa around 4.9, a generally ionized chlorinated organic compound under neutral conditions, has attracted great attention worldwide owning to its toxicity and carcinogenicity. PCP has been listed as a priority pollutant by the U.S.

Zerovalent iron (ZVI) and nanoscale zerovalen been widely applied to the remediation of neu organic chemicals (HOCs) such as trichloroethy nated biphenyls, and polybrominated diphenyhttp://dx.doi.org/10.1016/j.cej.2014.09.038 1385-8947/ 2014 Elsevier B.V. All rights reserved.enated chloriPBDEs) sorbed e HOCsKeywords:

Pentachlorophenol

Ni/Fe nanoparticles

Surfactants

Adsorption

Dechlorination

Electrostatic interaction electrostatic interaction between an electronegative phenolate group of PCP and the electropositive Ni/

Fe-CTAB. The increased sorption of PCP onto Ni/Fe surfaces by CTAB accelerated the reduction of PCP.

In addition, with CTAB, the observed bulky and soft surface of Ni/Fe NPs allows enhanced electron transfer from the zerovalent iron core. The removal mechanism of PCP is dechlorination for Ni/Fe-CTAB but, for bare Ni/Fe, adsorption is mainly responsible for the removal. The dechlorination pathways of PCP with Ni/

Fe-CTAB were investigated. The ortho position of chloride can be more easily reduced than other positions. Ni/Fe-CTAB NPs have a high potential to treat polychlorinated aromatics.  2014 Elsevier B.V. All rights reserved. 1. Introduction efficient and effective removal of PCP is urgently needed to facili-Available online 17 September 2014 by Ni/Fe. From removal ki when compared to that wh i g h l i g h t s  Adsorption and reduction contribute th  The optimum content of nickel to enha  CTAB significantly enhanced PCP remo  The increased sorption of PCP onto Ni/  CTAB enhanced the electron transfer fr a r t i c l e i n f o

Article history:

Received 26 May 2014

Received in revised form 7 August 2014

Accepted 10 September 2014val of PCP on Ni/Fe nanoparticles.

P removal on NZVI was around 0.5%. i/Fe nanoparticles. ces by CTAB accelerated PCP reduction.

Fe and the complete PCP dechlorination. a b s t r a c t

Pentachlorophenol (PCP), a general ionized chlorinated aromatic contaminant, was treated with Ni/Fe nanoparticles (NPs). An increase in the Ni/Fe dosage enhanced the removal of PCP. The most effective nickel percentage was 0.5%. Among the selected surfactants including carboxymethyl cellulose, Triton

X-100, and cetyl trimethylammonium bromide (CTAB), CTAB markedly enhanced the removal of PCPaDepartment of Agricultural Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, TaiwanAmphiphilic compounds enhance the de of pentachlorophenol with Ni/Fe bimetal

Cheng-han Lin a, Yang-hsin Shih a,⇑, John MacFarlane journal homepage: wwlorination nanoparticles le at ScienceDirect ering Journal elsevier .com/locate /cej eeriand contaminants [18–21]. Pd provided an excellent catalytic enhancement in reductive dechlorination of HOCs by ZVIs [22,23].

However, the high cost of Pd may restrict its wide application into the remediation [24]. Ni has also been widely used as a catalyst on ZVIs to dehalogenate HOCs. Since Ni containing catalysts could be potentially carcinogenic, they should be used for specific and controlled applications. Doong and Lai [25] reported that the dechlorination efficiency and rate constants of tetrachloroethylene (PCE)with ZVIwas enhanced by addingmetal ions, and followed the order Ni(II) > Cu(II) > Co(II). Although Ni/Fe particles have an effective dechlorination of HOCs [14,24], the four amended irons (including Ni/Fe) have slower removal kinetics of PCP when compared to unamended iron [26]. For the treatment of PCP inwater, the feasibility of using Ni/Fe nanoparticles (NPs) needs to be studied.

Various surfactants or polymers have been used to modify the iron nanoparticle surface and to increase the reactivity of ZVIs [27,28]. Wei et al. [29] used a biodegradable surfactant on NZVI to successfully treat chlorinated compounds at contaminated sites.

One nonionic surfactant (TritonX-100, TX-100) has been found to enhance the reductive dechlorination of hexachlorobenzene (HCB) by microscale Cu/Fe bimetal [30]. Moreover, cationic surfactants could be used to enhance degradation of chlorinated compounds treated with microscale zerovalent metals [31,32]. NZVI immobilized on the organobentonite (modified with cetyltrimethylammonium cations) can increase its reactivity toward chlorophenols due to the enhanced adsorption of chlorophenols onto organobentonite [33,34]. Anionic carboxymethyl cellulose (CMC) can enhance the reactivity of NPs for trichloroethylene (TCE) dechlorination [35]. Vitamin B12 facilitates NZVI to degrade several water contaminants. [36] Lee and Doong [37] and Parshetti and