An electrochemical cell consisting of a flow-through yttria-stabilized zirconia (YSZ) sensor and a flow-through Ag/AgCl reference electrode has been employed to measure pH of high-temperature acidic sulphate solutions relevant to the pressure acid leaching (PAL) of nickel laterites. In a previous study, this cell was used to measure pH of H2SO4, Al2(SO4)3-H2SO4 and MgSO4-Al2(SO4)3-H2SO4 solutions at 250oC. In this work, the solutions range in complexity from the binary MgSO4-H2SO4, NiSO4-H2SO4, and Al2(SO4)3-H2SO4, through the ternary MgSO4-Al2(SO4)3-H2SO4 and NiSO4-Al2(SO4)3-H2SO4, to the PAL process solutions, whereas the temperature ranges from 200oC to 250oC. The measured and theoretical pH values typically agree within less than 0.1 pH unit and 0.2 pH units in synthetic solutions and PAL solutions, respectively. This is an improvement over the results of the previous study in synthetic solutions, which show differences between theory and experiment as high as 0.4 pH units. The conversion of measured potentials into pH values is based on the new mixed-solvent electrolyte (MSE) speciation model of the OLI Systems software calibrated independently based on solubility measurements. Both Henderson’s equation and the exact definition of the diffusion potential were employed in treating the obtained experimental data. Experimental pH values calculated using the diffusion potentials evaluated by either approach are essentially the same. This finding suggests that Henderson’s equation, which is based on readily available limiting ionic mobilities, can be effectively used. Lithium chloride is found to be a suitable alternative to sodium chloride as the reference electrode solution for the measurement of pH of aluminium-containing solutions, because it did not induce precipitation of aluminium as an alunite-type compound. The experimental results indicate that the high-temperature behaviour of Ni, Co and Mn sulphates can be satisfactorily approximated with that of MgSO4. The experimental findings also support the postulation that acid should be added to a PAL process so that the solution pH is around 1 at the leach temperature, regardless of the feed composition. The cell can be used for hydrometallurgical process research and development on a laboratory scale with very satisfactory performance, provided that a well-behaved YSZ sensor is available.

An electrochemical cell consisting of a flow-through yttria-stabilized zirconia (YSZ) sensor and a flow-through Ag/AgCl reference electrode has been employed to measure pH of high-temperature acidic sulphate solutions relevant to the pressure acid leaching (PAL) of nickel laterites. In a previous study, this cell was used to measure pH of H2SO4, Al2(SO4)3-H2SO4 and MgSO4-Al2(SO4)3-H2SO4 solutions at 250oC. In this work, the solutions range in complexity from the binary MgSO4-H2SO4, NiSO4-H2SO4, and Al2(SO4)3-H2SO4, through the ternary MgSO4-Al2(SO4)3-H2SO4 and NiSO4-Al2(SO4)3-H2SO4, to the PAL process solutions, whereas the temperature ranges from 200oC to 250oC. The measured and theoretical pH values typically agree within less than 0.1 pH unit and 0.2 pH units in synthetic solutions and PAL solutions, respectively. This is an improvement over the results of the previous study in synthetic solutions, which show differences between theory and experiment as high as 0.4 pH units. The conversion of measured potentials into pH values is based on the new mixed-solvent electrolyte (MSE) speciation model of the OLI Systems software calibrated independently based on solubility measurements. Both Henderson’s equation and the exact definition of the diffusion potential were employed in treating the obtained experimental data. Experimental pH values calculated using the diffusion potentials evaluated by either approach are essentially the same. This finding suggests that Henderson’s equation, which is based on readily available limiting ionic mobilities, can be effectively used. Lithium chloride is found to be a suitable alternative to sodium chloride as the reference electrode solution for the measurement of pH of aluminium-containing solutions, because it did not induce precipitation of aluminium as an alunite-type compound. The experimental results indicate that the high-temperature behaviour of Ni, Co and Mn sulphates can be satisfactorily approximated with that of MgSO4. The experimental findings also support the postulation that acid should be added to a PAL process so that the solution pH is around 1 at the leach temperature, regardless of the feed composition. The cell can be used for hydrometallurgical process research and development on a laboratory scale with very satisfactory performance, provided that a well-behaved YSZ sensor is available.

Approximately 70% of the western world's known nickel reserves are contained in laterite ores, but only 30% of the world's nickel production comes from these ores. This is due to the lack of economically viable technology to extract the nickel from these ores. However, recent advances in pressure acid leaching technology have resulted in new commercial attempts to extract nickel and its valuable by-product, cobalt, from laterite ores. The commissioning of three nickel laterite projects in Western Australia in the late 1990s represents the first of these new generation nickel operations, with several other projects; in Australia and overseas, in various stages of development. Unfortunately, several technical issues have hindered full production in these new refineries. Some of these problems are directly attributable to the mixer-settler contactors used in the solvent extraction process. This has highlighted a need to develop alternative contactors for industrial use. Electrostatic Pseudo Liquid Membrane (ESPLIM) is an alternative, novel technique to conduct the solvent extraction process. It combines the basic principles of solvent extraction, liquid membrane and electrostatic dispersion into a simple, compact reactor that utilises many advantages of each technique. The aim of this study w as to develop a method of extracting and separating cobalt from an acidic nickel laterite leach solution using ESPLIM. Bench scale tests using synthetic and actual leach solutions have shown that: the design and construction materials of the baffle plate and electrodes have a significant effect on the performance of the reactor; an AC power supply provided better droplet dispersion than a DC power supply; an increase in the applied electric field strength above a critical value resulted in a decrease in the aqueous droplet size and an increase in residence tune. / These effects increased the extraction efficiency and the concentration of the loaded strip solution. However, further increases in applied electric field strength decreased efficiency due to excessive levels of swelling and leakage; the known extraction isotherms for cobalt and nickel apply in the ESPLIM technique; salts of soluble organic acids influence extraction efficiency by changing the aqueous pH and interfacial tension; the use of ammonia was found to be effective as a replacement for salts of soluble organic acids; the ESPLIM reactor can cope with large changes in the flow rates of both feed and strip solutions. However, an increase in the feed flow rate should be accompanied by a relative increase in the ship flow rate to maintain high extraction efficiencies; the baffle design has a significant impact on the levels of swelling and leakage; provided the electrostatic field strength is maintained and flow rates are increased proportionately to the size of the reactor, no significant scale-up issues were observed, indicating that the data generated in bench scale studies could be applied to plant scale contactors. The optimum conditions, devised as a result of this investigation, to extract cobalt from an acidic nickel laterite leach solution using the ESPLIM technique are as follows: an applied electric field strength of 5.5 kV/cm. a raffinate pH of 5.5, a solvent containing 10% Cyanex 272 with 5% TBP in Solvent HF diluent, a feed to strip flow ratio of approximately 5 and a 1 M H[subscript]2S0[subscript]4 strip solution. At these conditions, almost complete cobalt extraction is achieved after only two extraction stages. A comparable extraction using conventional mixer-settlers could only be achieved after five stages.

Leaching is the most widely used process for extraction of nickel metal from lateritic ores. In this study, nickel extraction from Manisa-G&ouml / rdes region laterites by hydrochloric acid leaching is aimed. The mineralogical analysis of sample showed that hematite, goethite, dolomite, quartz and smectite are the main minerals in the ore. Attrition scrubbing, cycloning and magnetic separation with permroll were used as preconcentration processes but results were unsatisfactory. HCl leaching experiments were conducted both at room temperature and at elevated temperatures. The effects of various parameters such as leaching duration, particle size, concentration of HCl, pulp density, Cl- concentration and temperature on nickel recovery were examined. The results showed that under the optimised leaching conditions (particle size: 100 % -1 mm, HCl concentration: 3 N, leaching duration: 3 hours, leaching temperature: 100 oC, pulp density: 1/30 solid to liquid ratio by volume) it was possible to extract 87.26 % of nickel in the ore.

ABSTRACT This study was aimed to investigate the operational conditions for stabilizing and recycling copper sludge in electronic industry by serially using acid leaching, cementation and ferrite methods. The physical/chemical characteristics of copper sludge were examined, and TCLP (Toxic Characteristics Leaching Process) tests were conducted. Results show that the copper sludge from electronic industry is weakly alkaline and consists of 6-15.8% Cu and 50-75% moisture. The TCLP tests show that copper in the sludge exceeds the regulation standard. Acid leaching tests indicate that the optimal combination of control factor levels yielding more than 99% of copper extraction is: 2.0 N in sulfuric concentration (A3), pH = 1.5 (B3), 90 minutes in treatment time (C3), and 50 oC in treatment temperature (D3). Moreover, the sediment of treated sludge fulfills the standards of the TCLP, and is thus a general industrial waste. Cementation tests indicate that the optimal combination of control factor levels yielding 96.87% of copper recovery and 92% of copper purity is: addition mole ratio of iron element Fe/Cu = 2.0 (A2), pH = 1.0 (B1), agitation speed = 200 rpm (C1), and 50 oC in treatment temperature (D3). Ferrite tests indicate that the optimal combination of control factor levels yielding more than 99% of copper removal is: addition mole ratio of ferrous sulfuric acid Fe2+/Cu = 10.0 (A3), pH = 9.5 (B2), air supply rate = 3.0 L/min (C3), and 80 oC in treatment temperature (D3). The cost analyses indicate that the expenses would be NT $7.45 for the acid leaching-cementation-ferrite process, less expensive than NT $ 8.0 for the solidification process given the same copper sludge. Thus, the proposed method in this study is competitive and feasible. Keywords: Copper sludge, Acid Leaching, Cementation, Ferrite Process, Recycling

Philosophiae Doctor - PhD / Zeolites are widely used as environmentally friendly solid catalysts or catalyst supports in the refining and petrochemical industries. ZSM-5 zeolite is composed of a three-dimensional medium pore structure (openings of 5-5.5 Å) with high silica content, high temperature stability and strong acidity making it a well-known and an established catalyst for several petroleum derived chemical processes such as cracking, aromatic alkylation, disproportionation, Methanol-to-Gasoline, isomerisation, etc. Nowadays, the synthesis of ZSM-5 zeolite from silica, alumina sources and structure directing agents (templates) is well known. Its synthesis is possible from fly ash, which is a low cost source of both silica and alumina. Fly ash is an inorganic residue resulting from the combustion of coal in electricity generating plants, consisting mostly of SiO₂ and Al₂O₃. ZSM-5 zeolite has not been synthesised from South African coal fly ash and the literature reports that fly ash-based ZSM-5 zeolite was synthesised only with tetrapropylammonium (TPA+) as structure directing agent and required an excessive amount of additional silica. The final ZSM-5 product was reported to still contain fly ash mineral phases after synthesis. This prevents the use of fly ash as a ZSM-5 zeolite precursor. Moreover, the synthesis of a high purity ZSM-5 zeolite from fly ash without additional silica has not been yet reported. This study aimed to synthesise high purity ZSM-5 zeolite from South African coal fly ash without additional silica, and with tetrapropylammonium bromide (TPABr), 1,6- hexanediamine (HDA) or 1-propylamine (PA) as structure directing agent. This aim was achieved by first optimising the synthesis of ZSM-5 zeolite from South African coal fly ash based on a formulation reported in the literature with fumed silica and TPABr as additional source of silica and structure directing agent respectively. Thereafter, the obtained optimum conditions were used to synthesise other fly ash-based ZSM-5 zeolite products by substituting TPABr with HDA or PA. Two routes of treating the as-received fly ash prior to the hydrothermal synthesis were applied in order to improve the quality of the final products or reduce the amount of the fumed silica that was used. The first route consisted of treating the as-received fly ash with concentrated H₂SO₄ in order to remove a certain amount of aluminium and increase the Si/Al in the acid treated fly ash solid residue but also remove some other elements such as Fe, Ca, Mg, and Ti which might have an undesirable effect on the product quality. The acid treated fly ash solid residue was used as ZSM-5 precursor with fumed silica as additional silica source and TPABr, HDA or PA as structure directing agent. The ZSM-5 zeolite products that were synthesised from the as-received fly ash as well as from the H₂SO₄ treated fly ash were treated with oxalic acid solution in order to reduce the aluminium content in the final products. The second route consisted of fusing the as-received fly ash with NaOH and treating the powder fused fly ash extract with oxalic acid solution. The obtained fused and oxalic acid treated fly ash extracts were used as ZSM-5 precursors without additional fumed silica and with TPABr, HDA or PA as structure directing agent. ZSM-5 zeolite was synthesised from the as-received South African coal fly ash not only with the commonly used structure directing agent TPABr but also with two other, lower cost structure directing agents, HDA and PA. The synthesis process did not generate any solid waste as fly ash was used as bulk, which could be a way of valorising South African coal fly ash. However, the final products contained some fly ash mineral phases such as mullite and quartz, and had poor physical and chemical properties compared to a commercial H-ZSM-5 zeolite. The treatment of the as-received fly ash with H₂SO4 resulted in fly ash-based ZSM-5 zeolite products with better physical and chemical properties than those of ZSM-5 zeolite products that were synthesised from the as-received fly ash. Moreover, the post-synthesis treatment of the fly ash-based ZSM-5 zeolite products with oxalic acid resulted in an increase in the Si/Al ratio, offering a post-synthesis route to adjust the acidity of the catalysts. However, mullite and quartz phases were still present in the synthesised products. Alternatively, high purity ZSM-5 zeolite was synthesised from the fused and oxalic treated fly ash extracts without additional silica and with TPABr, HDA or PA as structure directing agent. Moreover, these synthesised fly ash-based ZSM-5 zeolite products had similar physical and chemical properties to the commercial H-ZSM-5 zeolite. The synthesised fly ash-based ZSM-5 zeolite products were used as solid catalysts in the Methanol-to-Olefins (MTO) and Nazarov reactions. The ZSM-5 zeolite products that were synthesised from the H₂SO4 treated fly ash as well as fused and oxalic treated fly ash were successfully used as solid catalysts in the MTO and Nazarov reactions. The ZSM-5 zeolite products that were synthesised from the H₂SO₄ treated fly ash presented a similar trend in MTO and Nazarov reactions depending on the structure directing agent that was used, and the ZSM-5 zeolite that was synthesised with HDA as structure directing agent had the highest MTO and Nazarov conversion. However these catalysts deactivated more quickly compared to the commercial H-ZSM-5 zeolite. On the other hand, the zeolites that were synthesised from the fused and oxalic acid treated fly ash had a high initial MTO conversion equivalent to the commercial H-ZSM-5 zeolite. However, they deactivated after 5 h of time on stream due to diffusional constraints, because of their large crystal sizes. This study developed novel routes in the synthesis of high value zeolites from fly ash. ZSM-5 zeolite was synthesised from fly ash with structure directing agents other that TPA+ cation and had acceptable Brønsted acidity and high initial conversion in MTO and Nazarov reactions. This has not been yet reported in the literature. Moreover, for the first time a high purity ZSM-5 zeolite was synthesised from fly ash without additional silica and had similar properties to a commercial H-ZSM-5 zeolite. This constituted a breakthrough in the fly ash-based ZSM-5 zeolite synthesis procedure, which will promote the valorisation of fly ash through ZSM-5 synthesis due to avoiding the addition of silica source in the hydrothermal gel and preventing the presence of fly ash mineral phases in the final products. This study can have a significant economic and environmental impact in South Africa if the synthesis process is scaled up as it provides a potentially cheap and innovative way of using waste for making a high value green and acid catalyst, namely ZSM-5 zeolite that has several catalytic applications; and it promotes the valorisation of South African coal fly ash that is considered by many as waste material. / National Research Foundation (NRF)

The stoichiometric Self-propagating High-temperature Synthesis (SHS) thermite reaction involving magnesium oxide (MgO), titanium dioxide (TiO₂), and boron oxide (B₂O₃) forms titanium diboride (TiB₂) and MgO as final products. Selective acid leaching is used to remove the MgO leaving high purity TiB₂ powder. The SHS method to produce TiB₂ is attractive because of the relatively low temperature required to initiate the reaction, fast reaction time, and product purity. This study investigates the acid leaching of SHS produced MgO/TiB2 and a stoichiometric mixture of commercial MgO and TiB₂ powders. Leaching was conducted at 90° C, 60° C, and 30° C at pH levels of 4.0, 2.5, and 1.0 by introduction of concentrated aliquots of HNO₃. This method maintains a minimum pH target throughout the leaching process, thereby sustaining a dynamic concentration to remove the oxide. The optimal leaching conditions were determined to be at 90° C at a minimum pH target of 2.5 for the SHS produced product. At these conditions, conversion percentages of 83%-84% of MgO were measured with only trace amounts of TiB2 measured in the solution (less than 100 ppm). Conversion percentages for each leaching condition and dissolution mass of solid MgO and TiB₂ at each pH are also reported. Results from powder XRD confirm the removal of MgO and minimal dissolution of TiB₂, and indicate the formation of unidentified compounds. Inductively coupled plasma mass spectrometry (ICP) was used to analyze the ionic composition and extent of leaching. Scanning electron microscopy (SEM) was used to observe the particle morphology of the leached powders. / Master of Science

With a growing population but scarce primary phosphorus sources, recycling of the vital element has become an important research area throughout the last decades. Several streams in society are potential resources for recirculation but municipal sewage is considered one of the most available materials. With current technologies in wastewater treatment, over 95 % of the influent phosphorus is captured in the sludge along with a variety of other nutrients. However, due to increasing fractions of pharmaceutical residues and heavy metals also following the sludge, direct use as fertiliser is being phased out in most European countries in favour of extraction methods. Extraction of nutrients from the sludge is problematic mainly because of dewaterability difficulties. Thus, pretreatment of the material is required to access the desired components at a reasonable cost and energy consumption. Hydrothermal carbonisation (HTC) is a technology showing high potential for treatment of wet carbonaceous material without necessity of prior drying. The resulting product is hygenised, essentially free from pharmaceuticals and easily dewatered. In this Master’s thesis principal conditions for release of phosphorus from HTC converted digested sludge under acid leaching have been experimentally investigated. Dependence of time, temperature, dry solids (DS) content of HTC sludge and pH have been studied. Also, differences arising from acid type have been considered by comparing acidulation with sulphuric acid and hydrochloric acid. A short investigation of the recovery of the dissolved phosphorus from leachate by precipitation was also performed where calcium ions were added to both sulphuric and hydrochloric acid leachates. Extraction of phosphorus from HTC converted sludge has shown to be easier than from pure metal phosphates under comparable leaching conditions and pH values. Also, the dissolved phosphorus concentrations obtained in the presence of HTC converted sludge was higher than for theoretical equilibrium concentrations where all phosphorus is in the form of iron(III) or aluminium(III) phosphate. A maximum leachate phosphorus concentration was around 2500 mg/L, recorded in leaching experiments performed at a dry HTC product concentration of 10 % (w/w) in an extraction solution of water acidified with sulphuric acid. Leaching procedures performed at pH values between 2 and 1 with 1 and 5 % DS HTC product resulted in dissolution of 90 % of ingoing phosphorus at an acid charge of 0.5 kg H2SO4/kg DS HTC product. At this chemical charge, release of phosphorus from converted sludge is fast. Similar amounts of dissolved phosphorus were recorded after 15 min as after 16 h retention time. Possibly, time dependence becomes relevant at lower charges. The dissolution of phosphorus is negatively affected by temperature increases at moderate acid loads, and by possibly by hydrochloric acid at pH values below 2. Addition of calcium gave a dissolved phosphorus reduction of 99.9 % in both the sulphuric acid and hydrochloric acid leachates. Gypsum, CaSO4, also precipitates from the sulphuric acid leachate resulting in 67 % more dry mass. Due to high release of metals during acidulation, the precipitate was also contaminated with large fractions of metals in addition to calcium. In summary, this investigation has demonstrated that up to 90 % of the phosphorus content of the HTC converted sludge can be released by acid leaching, and almost 100 % of the phosphorus can be recovered from the leachate by precipitation with calcium ions.

A sucata eletrônica tem obtido crescente importância no cenário mundial de resíduos sólidos. Isso se deve não somente à sua toxicidade, mas também ao seu alto valor econômico, dado que as quantidades de metais presentes nas placas são expressivas (cerca de 36% em placas-mãe de computadores). A reciclagem da sucata eletrônica pode demandar uma ou mais etapas envolvendo a hidrometalurgia, em particular a lixiviação ácida, um dos processos economicamente viáveis. A fim de se estudar a influência da cominuição prévia da sucata, via moagem de alta energia, na cinética e na capacidade da lixiviação ácida de alguns metais de interesse, placas-mãe de computadores da marca Dell, do ano de 2006, foram cominuidas segundo duas rotas. Na primeira delas, houve cominuição apenas com o moinho de facas, tradicionalmente utilizado nessa etapa. Na segunda, fragmentos provenientes da cominuição em moinho de facas foram adicionalmente cominuídos em moinho planetário. Foram estabelecidos procedimentos similares de digestão e lixiviação das amostras das duas rotas, assim como nos respectivos resíduos de lixiviação. Os licores foram caracterizados quimicamente por ICP-OES. Concluiu-se que a cominuição adicional das placas-mãe em moinho planetário propiciou aumento substancial da cinética de reação e do rendimento da lixiviação do cobre, níquel e estanho, em razão do maior grau de cominuição atingido. Os rendimentos foram de 99,3 %, 98,9% e 93,6% no moinho planetário, contra 41,40 %, 60,2 % 83,9 % obtidos com o uso exclusivo do moinho de facas, respectivamente para o cobre, níquel e estanho. / The e-waste has a growing importance in the global scenario of solid waste. This is due to its toxicity and high economical value. The high value is provided by the valuable metals content on e-waste, whose concentrations are expressive (about 36% in weight on printed circuit boards). Many times, the recycling is complicated, requiring one or more steps of hydrometallurgy, particularly acid lixiviation, one of the economical viable process. In order to study the influence of previous comminution of e-waste by high energy milling, in chemical kinetic and in the acid leaching capacity of metals, Dell computer motherboards, from 2006, was comminuted in two different routes. In the first one, the motherboards were comminuted only in knife mill, a traditional way to comminute the e-waste. In the second route, the fragments that came from the knife mill were additionally comminuted in planetary mill. Similar procedures of digestion and leaching were established for both routes, as with the residues from both leaching. The leaching and digestion liquors were chemically characterized by ICP-OES. It was concluded that the additional comminution of motherboards in planetary mill propitiated a substantial increase in reaction kinetic and in metal leaching yield, cooper, nickel and tin, in function of comminution grade. The yields were 99.3 %, 98.9 % and 93.6 % in planetary mill, versus 41.4 %, 60.2 % and 83.9 % obtained in knife mill alone, respectively to cooper, nickel and tin.

Printed Circuit Board (PCB) industry is one of the two major Integrated Circuit (IC) part manufacturing industries in Taiwan, but it derives many environmental problems because large amount of chemicals and special materials are used in its process, especially copper sludge generated from wastewater treatment. Although the heavy metal sludge can be treated by solidification, heavy metals contained in the sludge may still be leached out due to longtime exposure to acid rain. Therefore, there are urgent needs of research and development of technologies regarding how to reduce both quantity and volume of the hazardous heavy metal sludge and how to recycle the valuable heavy metals. Acid leaching method, chemical exchange method and ferrite process are applied to study how to recycle and stabilize copper sludge of PCB industry. The ultimate goal is to achieve cleaning production and sustainable development by transforming the hazardous waste into valuable byproducts, reducing the amount of the waste and lowering the treatment costs. Experimental results show that a method is successfully developed to recycle copper from the sludge generated by PCB industry by using the combination of acid leaching, chemical exchange and ferrite process. Via this method, not only is pure copper powder recycled, but highly valuable nano-scaled catalyst-CuFe2O4 is also produced. Hence, the problem that copper sludge has nowhere to go is solved, as well as the high cost of catalyst in catalytic incineration is reduced to nearly zero. The achievements of this study are summarized as follow: (1) Characteristic analysis of industrial sludge Water content and pH of the sludge is 60% and 7.05, respectively. The drop in quantity of ignition is 23%. The screening test results show that particle size of the sludge varies from 0.4 £gm to 200 £gm, with D50 of 25.0 £gm. Cu, Pb, Cd, Zn, Ni and Cr are found in the sludge, and the biggest part of heavy metals is Cu, with a concentration of 158,000 mg/kg (dry basis), whereas the other heavy metals are all below 105 mg/kg (dry basis). (2) Study of recycling of pure copper powder The optimal operational condition of acid leaching method is that concentration of sulfuric acid is 2.0 N, temperature is 50¢J and treatment time is 60 minutes. Under this operational condition, more than 99% of heavy metals can be extracted to liquid phase and the sediment of treated sludge meet Toxicity Characteristic Leaching Procedure (TCLP) standards and therefore is considered as general industrial waste. The optimal operational condition of chemical exchange method is that molar ratio of Fe/Cu is 5.0, pH is 2.0 and treatment temperature is 50¢J. Under this operational condition, more than 95.0% of Cu can be recovered. The optimal operational condition of ferrite process is that Fe/Cu=10.0, pH=9.0, treatment temperature=80¢J, aeration rate=3 L/min/per liter waste liquid and reaction time = 30 min. Under this operational condition, TCLP concentrations of all heavy metals of both supernatant and sludge are well below regulatory standards, which proves that ferrite process is very effective. (3) Resourcing of spinel sludge In the potential of catalytic incineration of volatile organic compounds test, the sludge generated from ferrite process is used to catalyze the isopropyl alcohol (IPA). The catalyst is replaced by the same volume of glass wool on a reactive bed as a blank. Experimental result shows that the conversion of IPA is only 10% at 200¢J and 75% at 500¢J in the absence of catalyst under the conditions that IPA inlet concentration=1,700 ppm, space velocity=24,000 hr-1, O2 concentration=21%, and relative humidity=19%, which indicates that the destruction of IPA is associated with the consumption of much energy when no catalyst was used. But when ferrite catalyst is applied, IPA is decomposed completely at 200¢J, showing that the sludge has great potential of catalyst. (4) Synthesizing five VOCs catalyzing ferrite catalysts via ferrite process As to the synthesis of five ferrite catalysts in the laboratory, IPA conversion rate is higher than 58% at 200¢J. The sequence of IPA conversion from good to bad is Cu-ferrite catalyst > Mn-ferrite catalyst > Ni-ferrite catalyst > Zn-ferrite catalyst > Cr-ferrite catalyst, where Cu/Fe is most efficiency, with IPA conversion rate of 75% at 150¢J and 100% at 200¢J.