• Resources Recycling
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• v.1 no.1
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• pp.58-68
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• 1992

A process development for direct synthesis of high pure ZnO powders from zinc-bearing waste was investigated. This waste contains a 55% of zinc and it was extracted by the sulfuric acid(leaching). After removal of iron ion by precipitation from the zinc solution, the purification through a solvent extraction by the use of D2EHPA as an extractant was carried out. Then, loaded zinc in organic solution was stripped and precipitated simultaneously using a precipitant such as oxalic acid. Then, loaded zinc in organic solution was stripped and precipitated simulataneously using a precipitant such as oxalic acid. The synthesized $ZnC_2O_4$ powders by the precipitation stripping method was calcined to obtain more than 99.9% of ZnO powders. The effect of sulfuric acid concentration, leaching time, pulp density on the extraction of zinc was studied and the optimum conditions for the solvent extraction were obtained through the investigation of purification of zinc solution. The size, morphology and size distribution of synthesized $ZnC_2O_4$ powders were studied in terms of oxalic acid concentration, temperature, surfactant added, precipitation time, etc.

• Journal of Powder Materials
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• v.28 no.6
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• pp.497-501
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• 2021

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.43-47
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• 2000

A study on the remediation of heavily for ion contaminated soils from abandoned iron mine was carried out, using ex-situ extraction process. Also, oxalic acid as a complex agent was evaluated as a function of concentration, reaction time and mixing ratio of washing agent in order to evaluate Fe removability of the soil contaminated from the abandoned iron mine. Oxalic acid showed a better extraction performance than 0.1N-HCl, i.e., the concentrations of Fe ion extracted from the abandoned mine for the former at uncontrolled pH and the latter were 1,750 ppm and 1,079 ppm, respectively. The optimum washing condition of oxalic acid was in the ratio of 1:5 and 1:10 between soil and acid solution during l hr reaction. The total concentrations of Fe ion by oxalic acid and EDTA at three repeated extraction, were 4,554 ppm and 864 ppm, respectively. The recovery of Fe ions from washing solution was achieved, forming hydroxide precipitation and metal sulfide under excess of calcium hydroxide and sodium sulfide. In addition, the amounted of sodium sulfide and calcium hydroxide for the optimal revovery of Fe were 15g/$\ell$ and 5g/$\ell$ from the oxalic acid complexes, respectively.

• Resources Recycling
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• v.23 no.3
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• pp.37-43
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• 2014

A study has been made on the recovery of tin and copper from waste solder stripper by oxalate precipitation. With the increasing of the oxalic acid addition, tin was precipitated effectively and removed above 99.5% of tin when the oxalic acid, in an amount 1.0-1.5 times the stoichometric requirement, was added. But, in this case, only 2.0% of copper was precipitated and lead, iron were not precipitated. So, tin was selectively removed from the waste solution. With the increasing of the reaction temperature, the removal percentage of tin was increased and maximum value at arounf $60^{\circ}C$ and decreased with increase in the temperature any more. After filtering the precipitate and drying in oven, $SnO_2$ was obtained from the precipitate. After removal of tin in stripping solution, above 91% of copper was selectively removed by Cu-oxalate by addition of oxalic acid.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.996-1002
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• 1999

The oxalate precipitation of lanthanide and actinide by oxalic acid was investigated in the simulated radioactive liquid waste, which was composed of 17 elements of alkali, alkaline earth(Cs, Rb, Ba, Sr), transition metal(Zr, Fe, Mo, Ni, Pd, Rh), lanthanide(La, Y, Nd, Ce, Eu) and actinide(Np, Am) in nitric acid solution. The effect of concentrations of nitric acid and ascorbic acid on the precipitation yield of each element in the simulated solution was examined at 0.5 M oxalic acid concentration. The precipitation yields of the elements were usually decreased with nitric acid concentration, nevertheless, the precipitation yields of lanthanide and actinide were more than 99%. Palladium was precipitated due to the reduction of Pd(II) into Pd metal by the addition of ascorbic acid in the oxalate precipitation and then, the precipitation yields of Mo, Fe, Ni, Ba decreased by 10~20% with concentration of ascorbic acid. The reductive precipitation of Pd(II) into Pd metal by the addition of ascorbic acid into the simulated radwaste occurred at below 1 M nitric acid concentration and its yield showed maximum at the ascorbic acid concentration of 0.01~0.02 M. The hydrazine suppressed the reductive precipitation of Pd by the ascorbic acid.

• Journal of Environmental Science International
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• v.10 no.4
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• pp.299-304
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• 2001

For the remediation of the contaminated soil with heavy metals, Cd, Cr, Cu, and Pb, the reaction parameters were optimized. Tartaric acid (TA) and oxalic acid(OA) as a washing agent and recovery of metals, The optimum washing conditions of TA and OA were in the ratio of 1 : 20 between soil and acid solution during 2hr reaction under unbuffered pH solutions. At the optimized reaction conditions, the removal efficiencies were compared with that of 0.1 M HCl and ethylenediamine tetraacetic acid(EDTA). TA showed higher efficiency on the removal of Pb than that of EDTA, which established for the remediation of contaminated soil with Pb and Cd metals. The recovery of metal ions from washing solution was achieved by adding calcium hydroxide and sodium sulfide by forming the precipitation of metal hydroxide and metal slfied. Optimum amounts of sodium sulgide and calcium hydroxide were Cd = 25g/$\ell$, Cu = 5~10g/$\ell$ and Pb = 5~10g/$\ell$ for the washing solution of OA and 2~5g/$\ell$ for the washing solution of TA, respectively. The amounts of $Na_2S$ and $CA(OH)_2$ for the tartaric acid was less than that of oxalic acid.

• Advances in environmental research
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• v.5 no.2
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• pp.125-140
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• 2016

The paper is focused on the economic analysis of two hydrometallurgical processes for recovery of yttrium and other rare earth elements (REEs) from fluorescent phosphors of spent lamps. The first process includes leaching with sulphuric acid and precipitation of a mixture of oxalates by oxalic acid, the second one includes leaching with sulphuric acid, solvent extraction with D2EHPA, stripping by acid and recovery of yttrium and traces of other rare earths (REs) by precipitation with oxalic acid. In both cases the REEs were recovered as oxides by calcination of the oxalate salts. The economic analysis was estimated considering the real capacity of the HydroWEEE mobile's plant ($420kg\;batch^{-1}$). For the first flow-sheet the cost of recycling comes to $4.0{\euro}kg^{-1}$, while the revenue from the end-product is around $5.40{\euro}kg^{-1}$. The second process is not profitable, as well as the first one, taking into account the composition of the final oxides: the cost of recycling comes to $5.2{\euro}kg^{-1}$, while the revenue from the end-product is around $3.56{\euro}kg^{-1}$. The process becomes profitable if the final RE oxide mixture is sold for nearly $50{\euro}kg^{-1}$, a value rather far from the current market prices but not so unlikely since could be achieved in the incoming years, considering the significant fluctuations of the Res' market.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.963-969
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• 1992

This paper describes the feasibility for a direct production of zinc oxalate powders from zinc-loaded D2EHPA solutions combining the purification and the precipitation in one operation unit. This process has the potential as an alternative to conventional method for the synthesis of zinc oxide precursor particles from the hydrometal-lurgical processes. Zinc was extracted into D2EHPA in kerosene and then zinc-loaded D2EHPA solution was emulsified with oxalic acid-HCl solution to precipitate zinc oxalate powder, which was readily calcined to zinc oxide. The precipitation kinetics and yield were sensitive to experimental conditions. The morphology, size and size distribution of the zinc oxalate powders varied with zinc/oxalate ion riatio, temperature, and the presence of SPAN 60, which affected nucleation, growth, and the emulsion characteristics.

• Korean journal of food and cookery science
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• v.4 no.1
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• pp.27-32
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• 1988

The almost similar degumming effect was obtained by using oxalic acid instead of phosphoric acid, which also improves waste-water treatment. At this point, solution of Phosphoric, Acetic, Citric, Oxalic, and Nitric acid were used for degumming of rapeseed and soybean oil. Compared with Phosphoric(PA) and Oxalic acid(OA) were showed a simillar degumming effect in these vegetable oils. In rapeseed oil of 85% PA treating group and 5,10% OA fretting group, residual soap and phosphorus content in neutralized oil, color in bleached oil, and peroxide value and fatty acid content in deodrized oil were showed to simillar result. Soybean oil as well as rapeseed oil were showed to similar result. As a result, we could comfirmed substitutive possibility, which change PA into OA as a degumming agent. In the other hand, waste waters were obtained from 55% PA treating group and 10% OA treating group. Analytical result for this waste waters has showed a wide difference, especially in the BOD and COD. The amount of treating agents and time required in the precipitation seperation and chemical treatment each 3 and 1.7 times, which is PA treating group than OA treating group. We have investigated both the simillar degumming effect by OA solution and an alternative the pollution program means of a chemical treatment process is not possible.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.2
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• pp.85-90
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• 2018

For the recovering rare earths in the spent nickel-metal hydride batteries, 10 M NaOH is added to the solution leached with sulfuric acid. The rare earth powders were precipitated at rate of 98 % at the condition of pH 2.0 or less. The recovered rare earth complex precipitate increased the leaching rate to nitric acid by heat treatment at $800^{\circ}C$ for 4 hours. Subsequently secondary precipitation was performed by adding oxalic acid to the solution in which the rare earth complex precipitate was dissolved. The re-precipitated rare earth powders were converted into oxide form through heat treatment at $800^{\circ}C$ for 4 hours with purity of 99.5 %.