94 research outputs found
Design and construction of an industrial mobile plant for WEEE treatment: Investigation on the treatment of fluorescent powders and economic evaluation compared to other e-wastes
No full textThe main objective of this manuscript is the description of a mobile demonstration plant designed and built for the recovery of metals from waste of electrical and electronic equipment and other waste such as spent batteries and exhausted industrial catalysts. The plant was designed within the European FP7 framework HydroWEEE-demo (2012â2016) and can offer an effective proposal to addressing the problem of the electronic waste, reducing the environmental impact of their not correct disposal, recovering critical materials as rare earths and precious elements, and giving economic benefits, moreover by it, it is possible to overcome the problem of moving hazardous wastes from one country to another one. Details about the process to recover rare earths from fluorescent materials are presented. Two alternative treatments are showed with and without recirculation of the residual solutions. Economic analysis shows that with the actual product price (14 â¬/kg) only the process, in which solution recirculation is present, provides a return on the investment. Positive gain is possible if the plant works at its highest capacity and if the price growths up to 20 â¬/kg the gain increases about 20% of operating costs (process with recirculation, 2 batch/day). In the process without recirculation of the solution, to obtain the same ratio between gain and operating cost it is necessary that the price increases up to 26 â¬/kg. About other e-wastes, economic analysis has shown that the highest gain is provided from the PCB treatment
Adsorption onto activated carbon for molybdenum recovery from leach liquors of exhausted hydrotreating catalysts
No full textThis paper investigated molybdenum recovery from acid leach liquors of exhausted hydrotreating catalysts. Adsorption onto activated carbon was used to separate molybdenum from other metals contained in these leach liquors, namely nickel, cobalt and vanadium. Kinetic tests using Mo-bearing solutions denoted that the rate of adsorption depends on the amount of Mo in solution with an estimated order of reaction of 0.9 +/- 0.3. Equilibrium sorption tests showed that metal accumulation presents a bell-shaped behaviour as pH changes with a maximum sorption capacity around pH 5. Preliminary test in column reactor fed with Mo-bearing solution confirmed the sorption capacity estimated in batch tests (0.230 g/g). Sorption tests in batch reactors using leach liquor ([Mo] = 3.06 g/L, [V] = 5.84 g/L, [Ni] = 4.48 g/L, [Al] = 1.77 g/L) denoted that Mo can be quantitatively and selectively removed from solution (99% removal for Mo, 24 +/- 2% for Al, 19% for V and 0% for Ni) with no significant reduction of sorption capacity towards Mo (0.250 g/g). Preliminary sorption-desorption cycles denoted that Mo removal was larger than 90% in each cycle, whilst the other metals were minimally removed (Al and V) or completely rejected (Ni). (C) 2011 Elsevier B.V. All rights reserved
A hydrometallurgical process for the recovery of terbium from fluorescent lamps. Experimental design, optimization of acid leaching process and process analysis
No full textTerbium and rare earth recovery from fluorescent powder of exausted lamps by acid leaching with hydrochloridic was the objective of this study.In order to investigaste the factors affecting leaching a series of experimens was performend in according a full factorial plan with four variables and two levels. The fators studied were temperature, concentration acid, pulp density and leachin time. The results showed that temperature and pulp density were significant with positive and negative effect, respectively. The empirical mathematical model deduced by experimental data demonstrate that tebium content was completely dissolved under the following conditions: 90 °C, "M hydrochloridic acid and 5% pulp density; while when the pulp density was 15% an extraction of 83% could be obtained at 90 °C and 5% hydrochloridic acid. The mass balance of the process was calculated: from 1 ton of of initial powder it was possible to obtain 160 kg of a concentrate of rare earths having purity of 99%. The main rare earths elements in the final product was yttrium oxide (86.43%) following by cerium oxide (4.11%), lanthanum oxide (3.18%), europiumoxide (3.08%) and terbium oxide (2.20%)
Removal of tetramethyl ammonium hydroxide from synthetic liquid wastes of electronic industry through micellar enhanced ultrafiltration
No full textIn this paper, the separation of tetramethyl ammonium hydroxide (TMAH) from synthetic liquid wastes of
electronic industry is carried out by using a micellar enhanced ultrafiltration (MEUF) process. This
treatment represents the first step of an integrated process, aimed at the recovery of TMAH and
surfactant and water reuse. The laboratory tests are carried out with an ultrafiltration module using initial
solutions having a concentration of pollutant equal to 2 g/L and by adding sodium dodecyl sulfate as a
surfactant, at a concentration in the range 4–10 mM/L, that is, under and above its critical micellar
concentration (CMC). The experiments have been carried out at a fixed temperature of 25°C. The
obtained results showed that very good percentage removals of TMAH are achieved (99%), especially
when the surfactant was above the CMC
Secondary yttrium from spent fluorescent lamps: Recovery by leaching and solvent extraction
No full textThe separation of yttrium and calcium from acid leach liquor obtained from leaching of fluorescent lamp phosphors has been investigated by solvent extraction with D2EHPA and Cyanex 272 in kerosene. The preliminary tests suggested that D2EHPA was more efficient than Cyanex 272 for separation of yttrium. The experimental tests allowed to define the best process conditions, among those investigated, to separate and recover yttrium selectively. The best separation circuit included three-stage cross current extraction with 20%v/v D2EHPA in kerosene (O/A = 1/1, room temperature, 10 min of contact, pH 0.02) and stripping step in counter current with 1.5 M sulfuric acid (O/A = 1/1, room temperature, 30 min of contact). After stripping, yttrium was recovered as oxalate by the addition of oxalic acid. According to the experimental results, a hydrometallurgical process was developed. The final recovery from leach liquor was around 90% and the grade of the final product was 97.5% as hydrated yttrium oxalate. The main impurity was sulfur, 1.28% wt, in addition to traces of other elements such as Si (0.057% wt), Zn (0.015% wt), Eu (0.14% wt) and Fe (0.02% wt)
Advanced treatment of industrial wastewater by membrane filtration and ozonization
No full textThe present paper deals with nanofiltration (NF), ultrafiltration (UF) and ozonization pilot scale tests for revamping and improvement of an industrial plant that treats wastewaters coming from a wide range of hazardous industrial processes. Tests demonstrated that the best treatment is NF whose feed stream comes from sand filters rather than first ozonization stage before final discharge of the effluent. NF rejection coefficients resulted to be 31% for TDS, 94% COD, 9% Cl-, 47% surfactants, 66% phenols and 91% SO4 2-. UF was tested as NF pre-treatment but results were not so promising in terms of rejection and permeate flux, as well as fouling reduction. Other experimental tests were carried out in order to understand where to recycle the NF retentate: the best treatment in terms of COD reduction and biodegradability was ozonization followed by recycling to the physico-chemical stage. In the same manner, it was found that ozonization of the NF permeate is the best process solution before final treatment and discharge of the effluent. © 2012 Elsevier B.V
Yttrium recovery from primary and secondary sources: A review of main hydrometallurgical processes
No full textYttrium is important rare earths (REs) used in numerous fields, mainly in the phosphor powders for low-energy lighting. The uses of these elements, especially for high-tech products are increased in recent years and combined with the scarcity of the resources and the environmental impact of the technologies to extract them from ores make the recycling waste, that contain Y and other RE, a priority.The present review summarized the main hydrometallurgical technologies to extract Y from ores, contaminated solutions, WEEE and generic wastes. Before to discuss the works about the treatment of wastes, the processes to retrieval Y from ores are discussed, since the processes are similar and derived from those already developed for the extraction from primary sources.Particular attention was given to the recovery of Y from WEEE because the recycle of them is important not only for economical point of view, considering its value, but also for environmental impact that this could be generated if not properly disposal. © 2014 Elsevier Ltd
Fenton treatment of complex industrial wastewater: Optimization of process conditions by surface response method
No full textRemediation of industrial wastewaters represents a stringent problem in modern society, which requires particular understanding and ad hoc solutions. In this work, we performed extensive experimental study of chemical Fenton oxidation in order to understand the optimal operative conditions to be applied in real industrial wastewaters treatment.
We analyzed the effectiveness of chemical oxygen demand (COD) removal from different wastewaters within a wide range of initial COD content. We observed a maximum COD % removal of about 80%, assessing the efficiency of the process. In order to understand the role of different reagents in the final yield, we performed a factorial experimental approach on the Fenton's reagents (H(2)O(2) and Fe(2+)) and analyzed the results developing an analytical second-order model.
The model depends on three variables, namely: the initial [COD(i)] of the sample, the [COD(i)]/[H(2)O(2)] ratio and [H(2)O(2)]/[Fe(2+)] ratio. We obtained an accurate description of the COD % removal in different initial conditions, with a R(2) = 0.85.
In particular, we observed that optimal quantities of Fenton's reagents are a function of the initial COD of the treated wastes. (C) 2010 Elsevier B.V. All rights reserved
Rare earths from secondary sources: profitability study
No full textThe 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 (420 kg batch(-1)). For the first flow-sheet the cost of recycling comes to 4.0 (sic) kg(-1), while the revenue from the end-product is around 5.40 (sic) 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 (sic) kg(-1), while the revenue from the end- product is around 3.56 (sic) kg(-1). The process becomes profitable if the final RE oxide mixture is sold for nearly 50 (sic) 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
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