Heavy Metal Removal by Fixed-Bed Column – A Review Davendra Singh Malik [1] , Chakresh Kumar Jain [2] , Anuj Kumar Yadav [1], * www.ChemBioEngRev.de ª 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ChemBioEng Rev 2018, 5, No. 3, 1–8 1 Abstract Industrial wastewater often contains heavy metals that, if not removed, pose a risk to the environment. Therefore, an extended overview of different meth- ods for heavy metal removal by columns was con- ducted. Column studies are dependent on the flow rate, bed height and diameter, breakthrough curve, type of wastewater, and adsorbent. The fixed-bed column is most commonly used for metal seques- tration in aqueous media. Column studies have advantages due to industrial scale applicability and can treat large quantities of wastewater. Many kinetics models are applied in column studies like Adam-Bohart, Yoon Nelson, Bed Depth/Service Time, Thomas, and Clark. This paper deals with the use of modified or non-modified adsorbents for the treatment of metal-laden water and wastewater by column technique. Keywords: Adsorption, Breakthrough curve, Fixed-bed column, Heavy metals, Wastewater Received: September 27, 2017; revised: February 12, 2018; accepted: April 04, 2018 DOI: 10.1002/cben.201700018 1 Introduction Discharges of improper industrial wastewater containing metal have provoked serious environmental concerns. Industries like metal cleaning, plating, tanning, textile, battery making, pick- ling, and refining discharge millions of tonnes of highly pollut- ing effluents containing heavy metals into the aquatic environ- ment [1–2]. The metal-bearing wastewaters are generally discharged into rivers, lakes, streams, or other surface bodies. Contaminated wastewater primarily affects aquatic organisms including fishes and amphibians. Moreover, by using contami- nated wastewater for irrigation, the quality of soil and crop prod- ucts deteriorates as well as the microbial fauna of the soil [3]. The most common physico-chemical processes used to alle- viate metals from wastewater include chemical precipitation, ion exchange, membrane technology, flocculation, coagulation, flotation, electrodialysis, reverse osmosis, and oxidation/reduc- tion. These methods have limitations such as less effective removal of metal ions, high reagent requirement, cost effective- ness, applicability in certain concentration ranges, and disposal problems [4]. Among all techniques, biosorption has several advantages like metal selective effectiveness, trouble free opera- tion, easy revival, simplicity of design, and reprocessing of adsorbents [5–6]. In aqueous environments, biosorption is a surface phenomenon that deals with adherence of toxic metals, dyes, and pesticides in aqueous media. The effectiveness of the adsorption process for metal removal has been increased by natural adsorbents, either raw or modi- fied. Various adsorbents were used in column studyies such as waste pomace [7], rice husk [8], saw dust [9], mustard oil cake [10], and mushrooms [11]. Fixed-bed column studies are car- ried out due to practical applicability [9]. Column studies are easy in operation and design, obtain a high yield, and treat large quantities of wastewater. The most applicable technique in column studies is the fixed-bed column due to cyclic sorp- tion and desorption [12]. The breakthrough curve is a signifi- cant component of the column adsorption studies as it explains the effluent concentration-over-time profile [13]. The S-shape of the breakthrough curve depends on the nature of the waste- water treated [14]. The breakthrough curve for the adsorption of heavy metals were determined by models like Adam-Bohart, Yoon-Nelson, Bed Depth/Service Time as well as Thoma- s&Clark. This review article presents recent progress related to the application of column technique in heavy metal removal by adsorbents. It also describes the suitability of column models in industrial effluent treatment with flow rates and adsorption bed including the mechanisms involved in metal uptake. 2 Biosorption Columns 2.1 Continuous Flow Stirred Tank This is also known as continuous ideally stirred-tank reactor (CISTR). This bioreactor consists of a well-mixed vessel with ————— [1] Prof. Davendra Singh Malik, Anuj Kumar Yadav (corresponding author) Gurukula Kangri Vishwavidyalaya, Department of Zoology and Environmental Sciences, Haridwar, Uttarakhand 249404, India. E-Mail: anujyadav2007@rediffmail.com [2] Dr. Chakresh Kumar Jain National Institute of Hydrology, Environmental Hydrology Divi- sion, Roorkee, Uttarakhand 247667, India. These are not the final page numbers! &&