RECOVERY OF VALUE METALS FROM SPENT ZINC-CARBON BATTERIES

ABSTRACT
Spent primary batteries are known to contain metallic compounds that could be of value if recycled as well as harmful to man and the environment if not properly disposed. Also, the recovery of these value metals from the used batteries can reduce limited natural resource (ore) depletion. This research was carried out to investigate the recovery potential of Zinc and Manganese from spent zinc-carbon battery paste. Spent battery samples were collected around Samaru area of Sabon-gari LGA of Kaduna State. The samples were crushed, ground, sieved, washed and oven-dried. Quantities of dry samples were taken for x-ray fluorescence (XRF) analysis and chemical digestion. Chemical digestion (leaching) was done by studying some variable parameters: acid concentration, reducing agent concentration, temperature, stirring speed, solid-liquid ratio and time. Leached samples were then filtered and the filtrate taken for quantitative analysis of dissolved metals using atomic absorption spectrophotometer (AAS) analysis. Results show traces of heavy metals (lead, mercury and cadmium) and also significant amount of zinc and manganese in the solution. The optimum conditions for selective dissolution of zinc was found to be 2M nitric acid concentration, 10% hydrogen peroxide, 600C, 400rpm, 1:5 S/L and 1.5hrs, which yielded 4788.323mg/lit. For manganese, it was 1M nitric acid, 5% hydrogen peroxide, 600C, 400rpm, 1:5 S/L ratio and 1.5hrs giving a yield of 18042.67mg/lit while the optimum condition for simultaneous dissolution of zinc and manganese was found to be 1M nitric acid concentration, 5% hydrogen peroxide, 600C, 400rpm, 1:5 S/L ratio and 1.5hrs with a yield of 1225.648mg/lit zinc and 18042.67mg/lit manganese. The study therefore, showed that there is reasonable potential of zinc and manganese recovery from spent zinc-carbon battery.


CHAPTER ONE
1.0       INTRODUCTION
1.1       Background to Study
Large amount of primary cell batteries are discarded annually across the globe. In most West African countries, zinc-carbon and alkaline-zinc-manganese dioxide batteries have traditionally been the most popular among the rural folks and lately among the low to middle income populace in the urban areas owing to erratic power supply (Dankwah et al., 2015).

Primary batteries are the most common household portable energy source. They are also known as single-use batteries because they cannot be recharged and are disposed of after use, therefore, are considered the most common source of household hazardous wastes. The environmental impact of battery is not limited to the waste stream. Environmental impacts occur in the production, distribution and end-of-life phases of the batteries. Single-use batteries have significant environmental impact at every stage of their life cycle. Secondary batteries are rechargeable as they can be used repeatedly upon being recharged. Recharging occurs when electrical current is applied to the battery, reversing the chemical reactions that occur during battery use (Linden and Reddy, 2002).

Owing to its popularity and short lifespan, spent primary cells such as zinc-carbon and alkaline-zinc-manganese dioxide batteries can considerably function effectively as energy source to power household gadgets such as flash lights, television remote controls, radio receivers, etc. if recycled (Dittrich et al., 2012).

IRR (1992) stated that the logistics and viability of recycling household battery collection systems is mainly influenced by the current status of battery recycling technology for the various battery systems and the cost of battery recycling. Such knowledge will aid in evaluating the feasibility of implementing battery recycling programs. In fact, it is believed that the collection and recycling of used household batteries poses several unanswered technical and economic problems that need to be resolved before any widespread and implementation of such a program.

The metals of potential concern in the household batteries studies are cadmium, manganese, mercury, nickel, and zinc. In whatever disposal or management practice that is adopted for used household batteries, there is the potential for the release of one or more of these metals into the environment which may affect human health directly or indirectly or which may negatively impact the environment. Currently, used household batteries are almost exclusively disposed of in domestic waste, which is eventually incinerated or landfilled. Lately, the idea of used battery collection, separation and possible recycling is becoming another focus of attention (Veloso et al., 2005).

Any decision to recycle primary batteries must carefully weigh several factors including the low toxicity of the battery materials (e.g. steel, zinc and manganese), total energy requirement and the environmental impact associated with the collection, transport and recycling of the batteries, the amount and value of the metals recovered and the overall cost (Meskers et al., 2009).

According to NEMA (2002), landfill disposal of primary cell batteries does not pose a significant health or environmental risk based on over 20 years of battery experience and the results of various scientific studies. Almost a decade later, Khan and Kurny (2012) reported that “when zinc-carbon batteries (primary cells) are disposed of in a landfill, the elements of the spent batteries can undergo natural leaching, seep into the ground water, change water pH and cause contamination”. Further stated that the incineration of batteries also poses two major potential environmental concerns. The first is the release of metals (Zn, Pb and Hg if present) into the ambient air and the second is the concentration of metals in the ashes that must be land-filled. The stabilization process of the landfill on the other hand, is a costly process (Bernardes et al., 2004).

EPBA (2006) reported that the disposal of spent batteries represents an increasing environmental problem in terms of heavy metal contents when these devices are disposed of inadequately. This environmental problem is closely related to the battery market evolution; in 2003 the total portable battery weight in the East and West Europe was about 164,000 tons of which 50,197 and 99,138 tons were zinc-carbon and alkaline batteries respectively (30% and 60% of the total annual sales).

According to Nindhia et al. (2016), spent primary cell still contains ammonium chloride (NH4Cl2) which is mildly acidic that can disturb the balance of nature if the battery is carelessly discarded. Manganese dioxide (MnO2) is known as a hazardous material that can stain the human skin.

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Item Type: Project Material  |  Attribute: 103 pages  |  Chapters: 1-5
Format: MS Word  |  Price: N3,000  |  Delivery: Within 30Mins.
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