South African sands as an alternative to zero valent iron for arsenic removal from an industrial effluent: Batch experiments C. Trois *, A. Cibati School of Engineering, University of KwaZulu-Natal, Howard College Campus, Durban 4041, South Africa ARTICLE INFO Article history: Received 23 May 2014 Accepted 18 December 2014 Available online 24 December 2014 Keywords: Arsenic removal Natural iron-based adsorbent Zero valent iron Industrial effluent treatment Anions effect Kinetic ABSTRACT This work aimed to verify the potentials of two sands as a valid alternative of zero valent iron (ZVI) for the removal of arsenic from an industrial effluent. Batch experiments were conducted using Umgeni sand (US), Berea Red Sand (BRS), two types of zero valent iron (GmbH ZVI, and Connelly-GPM ZVI) and a mixture of BRS and GmbH ZVI. The experiments were carried out to study the removal kinetics of arsenic under semi-aerobic and anaerobic conditions and in the presence of sulfate, nitrate and phosphate anions. The GMP ZVI showed the best performance in terms of arsenic removal (100% of removal after 7h). BRS showed 61.75% of arsenic removal by itself and 86.32% of removal in combination with GmbH ZVI. The presence of oxygen increased the Arsenic removal efficiency for all substrates investigated. Sulfate and nitrate anions increased the removal efficiency while phosphate affected the arsenic removal efficiency. ã 2015 Elsevier Ltd. All rights reserved. Introduction Arsenic is a metalloid with particular physical–chemical properties. In nature, it is widely distributed in a number of complex minerals, mainly as arsenides of copper, nickel, and iron, or as arsenic sulfides or oxides. In water, arsenic is usually found in the form of arsenate or arsenite. Arsenic compounds are mainly used in agriculture and forestry as pesticides, herbicides, and silvicides [1,2]. The presence of arsenic compounds in groundwa- ter, and eventually in drinking water, is a serious environmental problem. In oxidizing conditions, arsenate (As(V)), is the predomi- nant arsenic form, while in reducing conditions, arsenite (As(III)), is the predominant one [3,4]. Due to its higher mobility in the environment, arsenite is considered more toxic than arsenate [2]. Long-term exposure in high levels of arsenic may cause skin changes, damage to major body organs and some types of cancer. Inorganic arsenic compounds are more toxic than organic arsenic compounds. Problems reported for the inorganic arsenic involve the respiratory system, gastrointestinal apparatus, skin system, and nervous system with acute and chronic toxicity and cancer of various apparatus [5]. A recent study, Tien-Hui et al., [6] demonstrated that inorganic arsenic significantly decreased cell viability and induced apoptosis in neuronal cells and also increased oxidative stress damage. WHO (World Health Organization) [7], established the drinking water limits of arsenic for human consumption to 10 mg LP 1 . This strict threshold forces municipal- ities that have problems with elevated arsenic concentrations, to apply efficient remediation techniques for the removal of arsenic. Several techniques have been proposed to treat waters, soils and wastes contaminated by arsenic. Among them, the most common are solidification/stabilization, vitrification, soil-washing extraction, coagulation-precipitation using iron and aluminum substances, membrane filtration, reverse osmosis, ion exchange, phytoremediation, bioremediation, permeable reactive barriers and adsorption [8–14]. Various adsorption materials have been used for the removal of arsenic from contaminated waters/wastewater, such as activated carbon, fly ash, ferric hydroxide, activated alumina, iron oxide coated sand, biomass adsorbent, resins, gels, silica and zero valent iron [15–19]. Studies [18,19] showed high arsenic removal capacity by ZVI and it has been concluded that could be used for remediation of contaminated industrial effluents and groundwater. A valid alternative to ZVI for arsenic removal is represented by natural iron-based minerals that by means of iron oxides such as ferric iron, lead to a co-precipitation of arsenic from water as ferric-arsenate [20,21]. In fact, iron oxide minerals being widespread in nature could lead to new efficient and cheaper technologies for arsenic removal from water. The overall aim of this work was to evaluate the efficiency and suitability of two South African sands (named Umgeni Sand (US) and Berea Red Sand (BRS) indigenous of the Durban area), to * Corresponding author. Tel.: +27 31 260 3055. E-mail address: troisc@ukzn.ac.za (C. Trois). http://dx.doi.org/10.1016/j.jece.2014.12.019 2213-3437/ ã 2015 Elsevier Ltd. All rights reserved. Journal of Environmental Chemical Engineering 3 (2015) 488–498 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece