24    DEVELOPMENT AND EVALUATION OF Mn
OXIDE-COATED COMPOSITE ADSORBENT FOR THE
REMOVAL AND RECOVERY OF HEAVY METALS
FROM METAL CONTAMINATED WASTEWATER
Huan-Jung Fan, Graduate Research Assistant
Paul R. Anderson, Associate Professor
Pritzker Department of Environmental Engineering
Illinois Institute of Technology, Chicago, Illinois 60616
INTRODUCTION
With 29% of the world reserves, coal is the most abundant fossil energy resource in the United
States. This amount of coal is equivalent to 2 trillion barrels of crude oil; more than twice the
world's known oil reserves. According to DOE's National Energy Strategy, the 770 million tons
of coal per year used in 1990 will increase 50% by 2010. This number will nearly double by
2030. In 1990, 55% of US electricity was produced by coal.1
Due to the increased use of coal, mobilization of heavy metals contained in coal is a growing
concern. Although metals are found in coal in relatively low concentrations, total emissions of
metals can be significant because of the extremely large quantities of coal consumed. Traditional
techniques to treat metal-contaminated wastewater involve some form of a precipitation process.
However, these processes have some potential disadvantages. For example, complexing agents
may inhibit the precipitation process, the optimal pH for precipitation varies from one metal to
another, and there are problems associated with sludge management.
An alternative treatment process is the removal of metals by adsorption onto oxide adsorbents,
such as aluminum oxides, iron oxides, and manganese oxides. However, one of the major limitations of the adsorption process is solid separation. Because a typical oxide adsorbent is in a colloidal form, it is difficult to separate from aqueous solution. One solution to this problem is to
prepare a granular composite adsorbent that can be used in a column process. Based on this concept, a composite adsorbent prepared from manganese and granular activated carbon (MnGAC)
may address some of these problems. The reason for choosing Mn oxides is that relative to Fe or
Al oxides, Mn oxides have a higher affinity for many heavy metals.2"4 Furthermore, several investigators have suggested applications for Mn oxides in water and wastewater treatment.4"7 Results from these studies suggest that Mn oxides can be used to synthesize an effective adsorbent
for metal removal. GAC, which has a high surface area, should provide an efficient surface for
the Mn oxide. At the same time, the Mn oxides can improve the metal adsorption capacity of
GAC. The resulting composite adsorbent (MnGAC) has good potential to become a very efficient way to remove metals from metal contaminated wastewater.
MATERIALS AND METHODS
This study includes two sections, adsorbent preparation and adsorbent characterization. A
composite adsorbent (Mn GAC) was prepared by coating Mn-oxide onto granular activated carbon (GAC). The adsorbent was characterized by batch adsorption capacity, batch kinetic, and
column tests. Reagent grade chemicals were used throughout this study unless specified, and all
labware was acid washed and thoroughly rinsed with double distilled water (DDW).
50th Purdue Industrial Waste Conference Proceedings, 1995. Ann Arbor Press. Inc.. Chelsea. Michigan 48118.
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