Abstract
This study investigated the applicability of industrial by-products such as steel slag (SS) and autoclaved aerated concrete (AAC) grains (<0.105, 0.105–2, 2–4.75 mm) as low-cost adsorbents for simultaneous removal of Cd2+ and Pb2+ in wastewater. A series of batch adsorption experiments was carried out in single and binary-metal solutions of Cd2+ and Pb2+ by changing the mixing proportions of SS and AAC grains. In addition, the effect of the liquid-to-solid ratio (L/S) on the removal of Cd2+ and Pb2+ in multi-metal solution was examined. Results showed that SS grains had a high affinity with Cd2+ in the single solution, while AAC grains had an affinity with Pb2+. In the binary solution, the mixtures of SS and AAC grains removed both Cd2+ and Pb2+ well; especially, the tested adsorbents of SS+AAC [1:1] and SS+AAC [1:4] mixtures achieved approximately 100% removal of both metals. Based on the results in the multi-metal solutions, the metal removal % and selectivity sequence varied depending on the mixed proportions of SS and AAC grains and L/S values. It was found that the SS+AAC [1:1] mixture of SS and AAC grains showed 100% removals of Cd2+, Pb2+, Cu2+, Ni2+, and Zn2+ simultaneously at L/S = 10 and 60.
Highlights
Due to rapid urbanization and industrialization, the discharge of wastewater containing toxic heavy metals from various sources such as industries, mines, vehicles, batteries, and metal-containing paints is increasing all over the world, especially in developing countries [1,2]
In order to examine the simultaneous removal of Cd2+ and Pb2+ in wastewater, this study investigated the adsorption characteristics of those metals onto the mixtures of steel slag (SS) and aerated concrete (AAC) grains in single and binary-metal solutions
Measured specific gravity (Gs ) values of SS grains were higher compared to AAC grains, and pH values showed that SS grains are alkaline in water due to the hydration reaction of CaO with a release of OH
Summary
Due to rapid urbanization and industrialization, the discharge of wastewater containing toxic heavy metals from various sources such as industries, mines, vehicles, batteries, and metal-containing paints is increasing all over the world, especially in developing countries [1,2]. Heavy metal ions are non-biodegradable and tend to accumulate in living organisms, and those are considered toxic or carcinogenic ions [3,4]. Inadequate treatments of toxic heavy metals such as Cd2+ and Pb2+ cause serious surface and groundwater pollutions and soil contamination [6,7,8] and various human diseases including acute or chronic poisoning, dermatitis, brain damage in children, and digestive tract cancer [9,10,11]. Cd2+ and Pb2+ can be considered the most commonly available and most harmful heavy metals to humans as well as the environment. Proper treatment of these heavy metals in wastewater is essential to protect public health and the environment
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