Electrochemical Separation and Purification of Metals from Waste Electrical and Electronic Equipment (WEEE)

This thesis reports on results of a novel process to recover metals selectively by electrodeposition by pumping aqueous acidic chloride solutions produced by leaching of shredded waste electrical and electronic equipment (WEEE) through the potentiostatically controlled cathode of an electrochemical reactor. The WEEE solutions contained low concentrations of precious metals, including Ag, Au, Pd and high concentrations of Cu. Electrodeposition from low concentrations of such dissolved metals requires electrodes with high mass transport rate coefficients and specific surface areas to increase cross-sectional current densities and optimise capital and operating costs. Hence, to recover gold from solutions with concentrations < 10 mol m-3 in the WEEE leachate, a three-dimensional cathode was used consisting of a circulating particulate bed of 0.5-1.0 mm diameter graphite particles, on which (AuIIICl4 - + AuICl2 -) ions were reduced. The temporal decay of the solution absorbance of AuCl4 - ions at 312 nm was recorded on-line by a quartz flow cell connected to a UV-visible spectrophotometer using fibre optics, enabling its time dependent concentration to be determined in real time. Total dissolved gold concentrations were determined by Inductively-coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results from the reactor experiments were modelled in terms of a mass transport controlled reaction in a plug flow electrochemical reactor operated in batch recycle with a continuous stirred tank reservoir. As copper is the dominant element in WEEE, and hence in the leach solution, its electrodeposition was investigated using an electrochemical reactor with a Ti/Ta2O5-IrO2 anode, cation-permeable membrane and a Ti mesh cathode in a fluidised bed of 590-840 μm glass beads to enhance mass transfer rates and to improve copper deposit morphologies. As for other metals, the effects were determined of cathode potential and solution flow rate on electrodeposition rates, charge yields, specific electrical energy consumptions, and deposit morphologies, imaged subsequently by scanning electron microscopy, and purities determined by X-ray fluorescence (XRF) and X-ray diffraction spectroscopy (XRD). While depleting CuII concentrations from 500 to 35 mol m-3, copper purities of > 99.79 %, as required for commercial purity Cu, were achieved with charge yields of 0.90 and specific electrical energy consumptions of 2000 kW h tonne-1. In addition, the circulating particulate bed cathode depleted solutions rapidly from 15 mol m-3 CuII ca. 100 ppm. Experiments with a rotating vitreous carbon cathode confirmed predictions from a kinetic model for a small electrode potential window within which to achieve selective electrodeposition of tin from synthetic SnIV-PbII aqueous chloride solutions, from which Pb could be electrodeposited subsequently. AlIII, FeII, ZnII and NiII remained in solution after the recovery of Au, Cu, Sn and Pb from the WEEE leachate. Unlike Al, it is possible to electrodeposit Fe from aqueous solution, and it was decided to add NaOH (+ air) to increase the pH to ca. 3.25 to precipitate ‘Fe(OH)3’, which was recovered by filtration. This option also enabled subsequent electro-co-deposition of Ni and Zn with high charge yields, as the higher pH decreased the driving force for H2 evolution. A one- dimensional mathematical model was developed in MAPLETM to predict the kinetics of Ni-Zn electro-co-deposition, which was validated experimentally. The model also considered the potential and concentration profiles in the cathode | electrolyte boundary layer for conditions in which migration and convective diffusion all contribute to overall transport rates, to predict the behaviour and optimize the process parameters of the electrochemical reactors

Calculation of filter lifetime using empirical model applied to hydrodynamic column for phosphate removal from greywater

Greywater is one of the point source pollution that negatively impact water resources if not properly treated. However, improvement of greywater quality can be potentially used for irrigation purpose. The main objective of this study is to calculate the lifetime for calcined waste mussel shell (CWMS) in hydrodynamic column. This study was performed using laboratory scale hydrodynamic column filled with CWMS to determine the breakthrough curve, adsorption capacity, accumulation rate and lifetime using empirical model for the adsorption of PO4 -3 onto CWMS from greywater. The bed height and flow rate that used in the experiment are 200 mm and 80 mL/h, respectively. The results demonstrate that breakthrough and exhaustion times are 12h and 18h, respectively. The empirical model was verified using experimental equilibrium data. The values of k1 and qmax calculated using model equations are 0.122 mg/g h2 and 0.0017 mg/g, respectively. On the basis of the results, CWMS can be economically basis media used as an adsorbent for the removal of PO4 -3 from greywater in the hydrodynamic column

Innovative Formulation and Characterisation of Grease Made from Waste Engine Oil

Lubricating grease is usually produced from mineral oil, making the relationship between grease and mineral oil unavoidable. Formulation of grease from waste oil can reduce the dependency of the grease industry on mineral oil as well as help to reduce the waste generation of used oil. This study aims to produce fumed silica (FS) grease from waste engine oil (WEO) and analyse the properties of the formulated grease. The method started with treating WEO to remove any contaminants in the used oil. After that, the greases are produced using a weight percentage ratio before being examined for consistency, oil separation, oil bleeding, FTIR (Fourier transform infrared spectroscopy) analysis, and corrosiveness. In terms of uniformity, oil separation, and oil bleeding, WEO percentage content had a substantial impact on the findings. The FTIR demonstrated that synthetic greases had the same spectra when evaluated between 500 cm-1 and 4000 cm-1. The grease's corrosiveness is low, as determined by class 1 corrosiveness toward the copper strip. However, the grease properties differ when consistency, oil bleeding and oil separation test is done. Higher oil content in grease produced high oil bleeding and separation but low consistency. As a conclusion of the results, fumed silica grease with oil percentages of 83 and 82 have the most grease-like features, showing that the grease fits the traits' requirements. Based on the investigation's findings, it was established that WEO may be used as a base oil in grease formulation and that the grease's properties are satisfactory

The Grease Formulation Using Waste Substances From Palm Oil Refinery And Other Industrial Wastes: A Review

Many applications use Spent Bleaching Earth (SBE) despite being considered hazardous waste from the palm oil refinery process. Its production increases yearly, similar to waste cooking oil (WCO). The SBE is known as a thickener in grease formulation. The same goes for red gypsum, waste motor oil, stearic acid, and lithium hydroxide monohydrate. They are all considered thickeners but have different durability in protecting base oil in grease. Then, previous studies revealed their performances with side effects detection against the environment and human bodies. Cooking oil is a heat transfer medium for serving foods with higher amounts of unsaturated fatty acids. The number of fatty acids might change after cooking oil consumption and become highly demanded due to the chemical properties of density, viscosity and fatty acids. Nowadays, people lack awareness of the importance of recycling palm oil waste. They intend to dispose of it instead of recycling it for sustainable energy resources. Therefore, this paper will discuss the grease formulation, contaminant available in WCO, its treatment, issues regarding different thickener consumption, treatment against Spent Bleaching Earth (SBE), and propose the safe thickener and additives for future intakes. This study found that adding Fume Silica (F.S.) as a thickener and Molybdenum Disulfide (MoS2) enhanced the grease stability. Further treatment against SBE (remove residue oil) and WCO (metal elements, undesired impurities and water content) is necessary for providing good quality formulated grease

Fabrication and characterization of poly(ether-block-amide)(Pebax-1657) and silicoaluminophosphate (SAPO-34) composite membranes

In the past few years, composite membrane has been introduced to cater the limitation of polymeric and inorganic membranes. However, the fabrication of ideal composite membrane with appropriate loading of filler remains challenging. Thus, the material selection as well as optimum loading with the conditions observed for the formulation of the composite membrane studied. In this present work, a series of poly(ether-block-amide) (Pebax-1657) and silicoaluminophosphate (SAPO-34) composite membrane with different loading of SAPO-34 particles (0-4 wt%) were fabricated. The physicochemical properties of the resultant membranes were investigated by utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Based on analysis, a good distribution of filler was obtained for the membranes loaded with 1 wt% and 2 wt% of SAPO-34 particles. Further increase of inorganic filler loading lead to the sedimentation and agglomeration of particle in the membrane, which may deteriorate the membrane performance in gas separation. Therefore, the optimum loading of inorganic particles in polymer phase play a major role in obtaining membrane with minimum defects ahead of gas separation performance tests such as for CO2/ethylene separation application

Electrochemical separation and purification of metals from waste electrical and electronic equipment (WEEE)

This thesis reports on results of a novel process to recover metals selectively by electrodeposition by pumping aqueous acidic chloride solutions produced by leaching of shredded waste electrical and electronic equipment (WEEE) through the potentiostatically controlled cathode of an electrochemical reactor. The WEEE solutions contained low concentrations of precious metals, including Ag, Au, Pd and high concentrations of Cu. Electrodeposition from low concentrations of such dissolved metals requires electrodes with high mass transport rate coefficients and specific surface areas to increase cross-sectional current densities and optimise capital and operating costs. Hence, to recover gold from solutions with concentrations 99.79 %, as required for commercial purity Cu, were achieved with charge yields of 0.90 and specific electrical energy consumptions of 2000 kW h tonne-1. In addition, the circulating particulate bed cathode depleted solutions rapidly from 15 mol m-3 CuII ca. 100 ppm. Experiments with a rotating vitreous carbon cathode confirmed predictions from a kinetic model for a small electrode potential window within which to achieve selective electrodeposition of tin from synthetic SnIV-PbII aqueous chloride solutions, from which Pb could be electrodeposited subsequently. AlIII, FeII, ZnII and NiII remained in solution after the recovery of Au, Cu, Sn and Pb from the WEEE leachate. Unlike Al, it is possible to electrodeposit Fe from aqueous solution, and it was decided to add NaOH (+ air) to increase the pH to ca. 3.25 to precipitate ‘Fe(OH)3’, which was recovered by filtration. This option also enabled subsequent electro-co-deposition of Ni and Zn with high charge yields, as the higher pH decreased the driving force for H2 evolution. A one- dimensional mathematical model was developed in MAPLETM to predict the kinetics of Ni-Zn electro-co-deposition, which was validated experimentally. The model also considered the potential and concentration profiles in the cathode | electrolyte boundary layer for conditions in which migration and convective diffusion all contribute to overall transport rates, to predict the behaviour and optimize the process parameters of the electrochemical reactors.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Hydrogen donor solvents in liquefaction of biomass: a review

The environmental impact of global warming, caused by greenhouse gases has also fuelled the needs to utilise biomass, as its energy utilisation creates less environmental pollution and fewer health risks than fossil fuel combustion. Liquefaction of biomass using hydrogen donor solvents is a promising route to obtain clean biofuel using various solvents at moderate to high temperature (250-460. °C) and pressure (150-320. bar). Solvents such as sub-and supercritical water, alcohol, decalin, glycerol and tetralin can be used as potential hydrogen donor to enhance liquid oil yield with a reduced of oxygen content. Supercritical water with its excellent transport properties as well as hydrogen donor capability leads to hydrothermal decomposition of biomass and enhancing various compounds depending upon operating parameters. The selection of alcohol as a solvent related to the action of hydrogen donor and to its alkylating ability. The hydrogen donor solvents provide an alternative to hydrogen gas as a reducing gas. The advantage of using hydrogen donor solvent is to stabilise the free radical in the biomass liquefaction and yielding a higher product conversion. Compared with non-hydrogen donor solvents, hydrogen donor solvents such as tetralin and decalin show significant improvement not only in conversion and product distribution to liquid but also on the quality of bio-oil (oxygen content) due to the improvement of hydrogenation and hydrocracking reactions with inhibition of polycondensation. The advantage of hydrogen donor solvents over the molecular hydrogen due to a lower strength bonding of C-H as compared to H-H bond. A review on performances of water, alcohols and other hydrogen donor solvents in liquefaction of biomass has been made. The yield of hydrogen donated in the reaction has also been reported

Gasification char residues management: Assessing the characteristics for adsorption application

Due to the world-wide energy crisis and economic issues, biomass has become a resource of global interest as an alternative to activated carbon (AC) produced using non-renewable feedstock (i.e. coal-based). The production of AC from biomass has been determined to be sustainable owing to the abundance of biomass resources on Earth. Biomass gasification has significantly gained market interest and was predicted to reach a value of USD 126 billion by 2023. A critical concern for the existing commercial gasification plants is the handling of char residues, which represent approximately 10% of the initial feedstock mass and are presently treated as waste. The conversion of these chars into AC that can be used for adsorption applications is a possible alternative. This review article focuses on evaluating the characteristic of the gasification char (GC) that is used for adsorption processes. The current AC production method was briefly reviewed. In addition, recent studies on adsorption using GC were explored and summarised

Optimisation of Copper Oxide Impregnation on Carbonised Oil Palm Empty Fruit Bunch for Nitric Oxide Removal using Response Surface Methodology

Oil palm empty fruit bunch (EFB) was successfully modified with phosphoric acid hydration followed by impregnation with copper oxide (CuO) to synthesize CuO modified catalytic carbon (CuO/EFBC) for low-temperature removal of nitric oxide (NO) from gas streams. CuO impregnation was optimised through response surface methodology (RSM) using Box-Behnken Design (BBD) in terms of metal loading (5-20%), sintering temperature (200-800˚C) and sintering time (2-6 hours). The model response for the variables was NO adsorption capacity, which was obtained from an up-flow column adsorption experiment with 100 mL/min flow of 500 ppm NO/He at different operating conditions. The optimum operating variables suggested by the model were 20% metal loading, 200˚C sintering temperature and 6 hours sintering time. A good agreement (R2 = 0.9625) was achieved between the experimental data and model prediction. ANOVA analysis indicated that the model terms (metal loading and sintering temperature) are significant (Prob.>F less than 0.05)

Optimisation of Copper Oxide Impregnation on Carbonised Oil Palm Empty Fruit Bunch for Nitric Oxide Removal using Response Surface Methodology

Oil palm empty fruit bunch (EFB) was successfully modified with phosphoric acid hydration followed by impregnation with copper oxide (CuO) to synthesize CuO modified catalytic carbon (CuO/EFBC) for low-temperature removal of nitric oxide (NO) from gas streams. CuO impregnation was optimised through response surface methodology (RSM) using Box-Behnken Design (BBD) in terms of metal loading (5-20%), sintering temperature (200-800˚C) and sintering time (2-6 hours). The model response for the variables was NO adsorption capacity, which was obtained from an up-flow column adsorption experiment with 100 mL/min flow of 500 ppm NO/He at different operating conditions. The optimum operating variables suggested by the model were 20% metal loading, 200˚C sintering temperature and 6 hours sintering time. A good agreement (R2 = 0.9625) was achieved between the experimental data and model prediction. ANOVA analysis indicated that the model terms (metal loading and sintering temperature) are significant (Prob.>F less than 0.05)