Arsenic removal from contaminated soils for recycling via oil agglomerate flotation Junhyun Choi a,1 , Eunseong Lee a,1 , Siyoung Q. Choi b , Seungwoo Lee c , Yosep Han a , Hyunjung Kim a,⇑ a Department of Mineral Resources and Energy Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756, Republic of Korea b Department of Chemical and Biomolecular Engineering, KAIST, Daejeon 305-701, Republic of Korea c Geo-environment Division, JIU Corporation, B-816 Gangseo Hangang Xi Tower, 401 Yangcheon-ro, Gangseo-gu, Seoul 157-801, Republic of Korea highlights  Oil agglomerate flotation process was developed for recycling contaminated soils.  Adding nonpolar oils increased the arsenic removal efficiency.  Fine particles were effectively removed by the addition of hydrocarbon oils.  Nonpolar hydrocarbons bridged fine particles and favorably attached to the bubble. graphical abstract article info Article history: Received 12 April 2015 Received in revised form 24 September 2015 Accepted 26 September 2015 Available online 9 October 2015 Keywords: Arsenic recovery Conventional flotation Oil agglomerate flotation Recycling Fine particles abstract In this study, a flotation process is proposed for separating the arsenic-bearing minerals to recycle the soil surrounding the Janghang refinery in South Korea, which contains a high level of arsenic. To maximize the arsenic recovery, several experimental parameters were systematically investigated. X-ray diffraction revealed that the contaminated soil was mainly composed of arsenopyrite (FeAsS), arsenic trioxide (As 4 O 6 ), arsenic pentoxide (As 2 O 5 ), and quartz (SiO 2 ). Flotation experiments with various concentrations of potassium amyl xanthate (PAX) showed that arsenic recovery increased with increasing PAX concen- tration. The addition of activators (Na 2 S, CuSO 4 , Na 2 S + CuSO 4 ) in pulp pH greatly increased the arsenic recovery. In addition, oil agglomerate flotation was conducted to enhance the arsenic recovery by improving the separation of fine particles. The results showed that arsenic recovery increased with increasing nonpolar oil concentration. Based on the results obtained from the optimization tests, a flota- tion process by which the arsenic-contaminated soils can be recycled was successfully designed. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Flotation is a physicochemical separation technique that separates hydrophobic particles from a mixture of hydrophobic and hydrophilic particles [1–3]. Flotation takes advantage of the distinct capture capability of a bubble surface to hydrophobic particles: more hydrophobic particles are easily attached to the bubble surface due to strong hydrophobic interaction whereas relatively fewer hydrophobic (or even hydrophilic) particles remain in the aqueous solution without the bubble attachment. However, when such a flotation technique is aimed at separating fine particles, it has not been very successful since its flotation efficiency becomes low [4–8]. In a flotation process, the bubble– particle collision and attachment, and the particle detachment from bubble surface simultaneously occur, which are known to govern the flotation efficiency [8,9]. It is generally accepted that http://dx.doi.org/10.1016/j.cej.2015.09.105 1385-8947/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +82 (63) 270 2370; fax: +82 (63) 270 2366. E-mail address: kshjkim@jbnu.ac.kr (H. Kim). 1 These authors equally contributed to this manuscript. Chemical Engineering Journal 285 (2016) 207–217 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej