This study investigates the recovery of valuable metals in an environmentally friendly way that reduce environmental pollution and human exposure to the toxic chemicals.
The global production of electrical and electronic waste (e-waste) is increasing rapidly and is expected to accelerate globally. Globally e-waste is classified as hazardous material and therefore should be managed properly to avert pollution and human e-waste is one of the waste streams difficult to manage global. In Nigeria, it is expected that the production of e-waste will increase by 60%, therefore, a three-pillar strategy of waste prevention, recycling and reuse has been suggested to minimize the environmental impact and promote the efficient utilization of wasted resource.
Table of Contents
1.0 INTRODUCTION
1.1 BACKGROUND TO STUDY
1.2 STATEMENT OF THE RESEARCH PROBLEM
1.3 JUSTIFICATION
1.4 AIM AND OBJECTIVES
1.5 SCOPE AND LIMITATION OF THE STUDY
2.0 LITERATURE REVIEW
2.1 ELECTRONIC-WASTE RECYCLING
2.2 GENERAL DRIVING FORCE FOR E-WASTE PROCESSING
2.3 ENERGY AND RESOURCE CONSERVATION
2.4 E-WASTE PROCESSING
2.5 METALLURGICAL PROCESSES FOR THE EXTRACTION OF METALS FROM E-WASTE
2.5.1 Hydrometallurgical Processes
2.5.2 Microbial Biotechnological Approaches To Recover Metals From Waste
2.6 DESIGN FOR RESOURCE (DFR) EFFICIENCY
3.0 MATERIALS AND METHOD
3.1 MATERIALS USED
3.1.1 Equipment Used
3.2 METHODS
4.0 RESULTS AND DISCUSSION
4.1 LEACHING EFFECTS OF STUDIED PARAMETERS ON METALS EXTRACTION
4.2 CONCLUSION
4.3 RECOMMENDATIONS
Research Goals and Topics
This research aims to investigate a sustainable and efficient method for recovering valuable metals from computer printed wiring boards using a hydrometallurgical approach with nitric acid and hydrogen peroxide to minimize environmental impact and promote resource conservation.
- Hydrometallurgical extraction processes for e-waste
- Leaching efficiency of metal recovery systems
- Optimization of chemical parameters (time, temperature, acid concentration)
- Reduction of environmental pollution from electronic waste disposal
Excerpt from the Book
2.5.1 Hydrometallurgical Processes
Various investigators studied the extraction of metals from e-waste using hydrometallurgical routes (Chehade et al., 2012; Dhawan et al., 2008; Dhawan et al., 2009; Delfini et al., 2011; Park et al., 2009). These routes are based on traditional hydrometallurgical technology of metals extractions from their primary ores. Similar steps of acid or caustic leaching are employed for selective dissolution of metals from e-waste. The pregnant solution is separated and purified for the enrichment of metal content thereby impurities are removed as gangue materials. The isolation of metal of interest is conducted through solvent extraction, adsorption and ion exchange enrichment processes. Finally, metals are recovered from solution through electrorefining (electrometallurgy) or chemical reduction processes (Sadegh et al., 2007; Ritcey, 2006; Yang, 1994; Shamsuddin, 1986; Tavlarides, 1985). Cui and Zhang (2008) reviewed the processes for recovering metals from e-waste. Hydro- and pyrometallurgical processes were evaluated and discussed. It has been reported that hydrometallurgical processes have additional benefits compared to pyrometallurgical processes because they are more exact, predictable, and easily controllable (Paretsky et al., 2004).
Solvents especially halides, cyanides, thiourea and thiosulfates are used for the leaching of PMs from their primary ores. Process factors including pH, temperature and stirring control the dissolution of metals from their primary ores. The recovery of PMs from the leached solution is carried out by cementation, solvent extraction, adsorption on activated carbon, and ion exchange methods. Similar techniques could be employed for extracting metals from e-waste, however, its complex nature makes the process complicated compare to natural ores. Park et al. (2009) proposed a hydrometallurgical method for recovering PMs from e-waste. Aqua regia was used as leachant and a fixed ratio of 1/20 between metals and leachant was exercised. Silver and palladium were extracted during the first stage with 98% and 93% recovery, respectively. For gold, a liquid-liquid extraction method was adopted with toluene and a recovery of 97% was reported.
Summary of Chapters
1.0 INTRODUCTION: Discusses the global rise in e-waste production and the negative environmental impact of improper disposal methods, establishing the need for effective recycling.
2.0 LITERATURE REVIEW: Examines current recycling standards, hydrometallurgical and pyrometallurgical techniques, and design for resource efficiency strategies in the electronics industry.
3.0 MATERIALS AND METHOD: Details the experimental setup, collection, dismantling, grinding, and the two-stage leaching process using nitric acid and hydrogen peroxide.
4.0 RESULTS AND DISCUSSION: Analyzes the percentage yield of metal recovery and the correlation between leaching variables and the final extraction efficiency of unwashed versus washed samples.
Keywords
E-waste, Hydrometallurgy, Metal Recovery, Nitric Acid, Hydrogen Peroxide, Sustainability, Recycling, Printed Wiring Board, Leaching, Precious Metals, Environmental Pollution, Waste Management, Electronic Component, Secondary Raw Materials, Chemical Extraction.
Frequently Asked Questions
What is the primary focus of this research?
This research focuses on the hydrometallurgical extraction of valuable metals from computer printed wiring boards using nitric acid and hydrogen peroxide as a primary solvent and reducing agent.
What are the central themes of the work?
The core themes include e-waste management, environmental sustainability, recycling economics, and the optimization of chemical metallurgy processes for secondary resource recovery.
What is the main research objective?
The primary aim is to establish a profitable and efficient metal recovery process that reduces the need for traditional hazardous e-waste incineration and environmental degradation.
Which scientific methodology is employed?
The study utilizes a hydrometallurgical method involving mechanical preprocessing (dismantling, grinding, sieving) followed by acid leaching and subsequent quantitative analysis using Atomic Absorption Spectrophotometry (AAS).
What does the main body of the work cover?
The main body provides extensive background on e-waste, reviews existing recycling technologies, details the specific experimental procedures used, and presents test results regarding leaching variables.
Which keywords define this document?
Key terms include e-waste, hydrometallurgy, nitric acid, metal recovery, printed wiring boards, and environmental sustainability.
Why are unwashed samples showing different yields than washed ones?
The research notes that unwashed samples often exhibit higher comparative values of metal content in the final extract, suggesting that the initial processing state significantly impacts the solvent-leachant efficiency.
What role does hydrogen peroxide play in the process?
Hydrogen peroxide serves as a vital oxidizing/reducing agent in the solvent mixture, enhancing the dissolution rate of valuable metals from the printed board powder.
Are there limitations reported in the study?
Yes, the study mentions limitations such as the inability to detect specific rare earth element concentrations in the laboratory due to the lack of necessary equipment (lamps) and the need for further studies on purification.
- Quote paper
- Ogubuike Jude (Author), 2019, Extraction of Valuable Metals from Printed Wiring Board of a Computer Using Nitric Acid and Hydrogen Peroxide, Munich, GRIN Verlag, https://www.grin.com/document/1239246
