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 | Size: 103 pages | Chapters: 1-5
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