Search

Hydrodynamic cavitation is a promising technology for several applications, like disinfection, sludge treatment, biodiesel production, degradation of organic emerging pollutants as pharmaceutical, and dye degradation. Due to local saturation conditions, cavitating liquid exhibits generation, growth, and subsequent collapse of vapor-filled cavities. The cavities' collapse brings very high pressure and temperature; this last aspect is essential in some chemical processes because it induces the decomposition of water molecules into species with a high oxidation potential, which can react with organic substances. Properly exploiting this process requires a highly accurate prediction of pressure peak values. To this purpose, we implemented a multi-phase Eulerian–Lagrangian code to solve the fluid-dynamic problem, coupled with the Rayleigh–Plesset equation, to capture the evolution of bubbles with the required accuracy. The algorithm was validated against experimental data acquired with optical techniques for different cavitation-shedding mechanisms. Then, we used the developed tool to investigate the decoloration of organic substances from a cavitation Venturi tube operating at different pressure. We compared the obtained results with the experimental observation to assess the reliability of the developed code as a predictive tool for cavitation and the possibility of using the code itself to assess scale-up criteria for possible industrial applications.

In the present work, the potentiality of the hydrodynamic cavitation (HC) for the degradation of organic pollutants from industrial effluents has been studied. Cavitation is a phenomenon of formation, growth, collapse of microbubbles or cavities, in a few milli- to microseconds and releases large magnitude of energy in a short span of time. The main chemical effects of HC are the generation of highly reactive free radicals in the aqueous environment; it is possible to exploit these radicals for the intensification of chemical processes such as degradation of the water pollutants. HC represents an innovative advanced oxidation processes that can replace or be combined with the traditional oxidation processes. Lab experiments have been performed to remove pollutants as dyes (methyl orange and methylene blue) that can be present in textile effluents. The core of the experimenal apparatus was a Venturi Tube having a diameter of 12 mm and a convergent of 2 mm. In order to investigate the potentiality of HC, the effect of several operative conditions was investigated as contaminant concentration, inlet pressure and time. Other experiments have been conducted adding hydrogen peroxide, iron and titanium oxides in order to monitor the effect of hybrid treatment on pollutant degradation.

Quantitative determination of most economic valuable metals in waste is the first fundamental operation of evaluating the feasibility of recycling processes. Field-portable X-ray fluorescence spectrometers (FPXRFs) represent a more practical, efficient, and economic tool in determining the elemental composition of samples with respect to conventional analytical techniques, such as atomic absorption spectrometry (AAS) and inductively coupled plasma emission spectrometry (ICP). In this paper, quick and smart determination of gold content in printed circuit boards (PCBs) of waste mobile phones was studied. The aim of the research was to combine the practicality of FPXRFs with the reliability of quantitative spectrometry analysis and evaluate the error between the two techniques. Several samples (33) of PCBs were ground to a size below 0.5 mm, and then, the powders were analyzed by FPXRFs at different acquisition times with five replications for each sample. The same analyzed samples then underwent chemical attack to determine the quantitative gold content by AAS. The obtained results were associated with FPXRFs response with the purpose of realizing a calibration curve (100–1000 mg/kg Au). The curve was validated for accuracy and precision by other PCBs waste samples, the control samples were added as standards to obtain a more reliable calibration curve. The curve was evaluated with RPD classification, regression linear, and Bolt–Altman analysis.

Typical methods for the treatment of waste pickling solutions include precipitation by alkaline reagents, most commonly calcium hydroxide. As a result, large volumes of galvanic sludge form, containing iron, calcium, sulphates, and a relatively small quantity of zinc (&lt, 20%), making Zn recovery not profitable. In summary, state-of-the-art Zn galvanization processes entail the loss of valuable metals and the irrational and expensive handling of spent pickling solutions (SPSs). The resulting conclusion is that there is room for a significant improvement in the way SPSs are treated, with the double goal of enhancing Zn galvanization methods&rsquo, economic viability and achieving a lesser impact on the environment&rsquo, s processes. The experimental results show that it is possible to use SPS as a coagulant to treat the process wastewaters, kept separated, and added with sodium hydroxide. The results in obtaining precipitates with Zn contents higher than 40%, increasing the added advantage of making Zn recovery profitable. The results show the possibility of using SPS as a coagulant in the process of physical-chemical wastewater treatment and sodium hydroxide to obtain a precipitate with a zinc content of more than 40%.

This study compared the sustainability of six alternatives for the treatment of industrial wastewater from a gasifier, considering both environmental and economic aspects by the approaches of: uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). The processes have been developed under the zero liquid discharge approach and included a chemical removal of pollutants by using Fenton and neutralization, evaporation and crystallization to concentrate salts and stripping for the removal of ammonia from distillate of evaporation step and recover water useful for industrial reuses. The scenarios differed for the type of utilities used for the operation (steam and hot water from thermal waste) and from an optimization of the crystallization that provided a reduction of the amount of waste and an energy recovery from distillate. LCA indicated that the six scenarios produced comparable results, since the common chemical treatment (raw material and waste disposal) causes the highest contribution. The optimal scheme used hot water as utilities and had an optimization of the crystallization section (scenario B2), this options allowed a decrease of emission to air of 25% and reduction of 15% of deposited goods. Scenario B2 is much more financially attractive than the other proposed treatment, having a total cost of 123 €/t, with a reduction of 17% respect to the current disposal of 150 €/t. LCA and LCC results prove the effectiveness of thermal waste use as utilities for the wastewater treatment operations and the optimization of crystallization unit is the most environmentally and economically favourable alternative.

The article reports the preliminary results obtained in a pilot plant that treats a spent tetramethylammonium hydroxide (TMAH) solution, a typical chemical compound used in the microelectronics industry and massively present in wastewaters. The plant is based on three aerobic bioreactors in series, fed by a real TMAH solution effluent from the semiconductor industry. The plant ran for 14 days in continuous operating mode with a flow rate of 5 L/h; then, the plant switched to batch mode. The microbial population was analyzed to determine if microbial population changes occurred. The results indicated that TMAH degradation only occurred during the batch operation mode. The TMAH reduction was about 80% in the first reactor and complete (100%) in the second and third bioreactors. At the same time, the microorganisms increased their mass by 338%, 58%, and 1% in the first, second, and third bioreactor, respectively. The degradation intermediates confirmed the efficiency of the process and the possible reuse of water, which closes the water loop's circularity. Furthermore, a nitrate concentration of 150–250 mg/L was found in the last two bioreactors: this implies a significant presence of ammonium-oxidizing bacteria. Community genomic analysis was conducted to detect changes in the microbial community due to changes in operating conditions that could cause reactor failure if methylotrophs were washed out or outcompeted by unspecific bacteria.

Rare earth elements (REEs), independently by the economic value, have a strategic importance and are involved, as critical materials, in the competition for their supply. An innovative process with the introduction of a preliminary physicochemical treatment was proposed. The mechanical activation of waste of fluorescent powders was performed by a vibratory disc mill at different experimental conditions to optimize the process. The mechanical forces induced to the powders cause crystal structure defects with a consequent increase of rare earths leachability. Factorial experimentations and analysis of variance were studied to determine the significant effects of the investigated factors (mechanical activation time, sulfuric acid concentration, pulp density and leaching temperature), especially for terbium dissolution. The preliminary activation allows to increase terbium dissolution of 35%. Then, according to the best conditions the subsequent operations of precipitation and calcination were performed obtaining a purity of 98.3% as rare earth oxides. Based on the experimental results, the flowsheet for rare earths recovery has been proposed and implemented by SuperPro Designer, a simulation software for process analysis and mass-energy balances. Finally, this paper reports a comparison between the present process with the mechanical pre-treatment and the alternative method based on thermal pre-treatment.

Biodiesel production calls for innovative solutions to turn into a competitive process with a reduced environmental impact. One of the process bottlenecks stands in the immiscibility of oil and alcohol as raw materials, so mixing process largely impacts the overall process cost. This process step, if carried out by using hydrodynamic cavitation, has the possibility to become a benchmark for large scale applications. In this paper a process analysis of biodiesel production scheme is developed starting from two different feedstocks, virgin oil and waste cooking oil. At the first the traditional process scheme has been simulated, in a second simulation, the reactor for the biodiesel production is interchanged with a hydrodynamic cavitation reactor. In the paper, the comparison between the traditional and innovative process by using life cycle costing approach has been presented, thus providing indications for industrial technological implementation coming from a professional tool for process analysis. It is worth noting that the introduction of hydrodynamic cavitation reduces of about 40% the energy consumption with respect to the traditional process. As regards the total treatment costs, when using virgin oil as feedstock, they were in the range 820–830 €/t (innovative and traditional process, respectively); while starting from waste cooking oil the costs decreased of about 60%, down to 290–300 €/t (innovative and traditional process, respectively).

The paper reports on a possible way to recycle fluid catalytic cracking catalysts (FCCCs), widely used in oil refining operations. This research proposes a novel approach that leads to a near zero-waste process. The spent FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80°C, for 3 h with a solid to liquid ratio of 20 %wt/vol. The leaching yields for cerium and lanthanum were in the range 69-82 %. The solid residues from the leaching stage were used as base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62 % and purity of 97 %vol. The zeolites synthesized from spent FCCC represent a feasible solution to recover such industrial waste.

In this research, micellar enhanced ultrafiltration (MEUF) is tested as a seawater pre-treatment before entering RO. The experimental tests were performed by means of monotubular ceramic membranes of 210 kDa and 1 kDa. Boron is removed from the water flow using sodium dodecyl sulphate as a surfactant. The synthetic solutions contain 5 mg/L of boron and SDS concentrations are equal to 1.15 g/L and 2.88 g/L, under and above the critical micellar concentration, respectively. Experimental data showed that MUEF is efficient in removing boron, with best performances obtained at low pressure, with a low or null surfactant concentration for 1 kDa membrane and a high surfactant concentration for 210 kDa membrane. Moreover, experimental results have been used to perform a preliminary process analysis for a hypothetic sea-water desalination plant, with MEUF as a pretreatment for the RO section. The results showed that the MEUF guarantees a boron concentration after RO below the allowed threshold, by using a single step osmosis; moreover, in this way it was possible to reduce the energy consumption thus resulting in an appreciable reduction of carbon footprint as well as of the unit cost of water.

The 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 (2012–2016) 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 €/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 €/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 €/kg. About other e-wastes, economic analysis has shown that the highest gain is provided from the PCB treatment.

The 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).

According to the International Energy Agency (IEA), only a tiny fraction of the full potential of energy from biomass is currently exploited in the world. Biogas is a good source of energy and heat, and a clean fuel. Converting it to biomethane creates a product that combines all the benefits of natural gas with zero greenhouse gas emissions. This is important given that the methane contained in biogas is a more potent greenhouse gas than carbon dioxide (CO2). The total amount of CO2 emission avoided due to the installation of biogas plants is around 3380 ton/year, as 1 m3 of biogas corresponds to 0.70 kg of CO2 saved. In Russia, despite the huge potential, the development of bioenergy is rather on the periphery, due to the abundance of cheap hydrocarbons and the lack of government support. Based on the data from an agro-industrial plant located in Central Russia, the authors of the article demonstrate that biogas technologies could be successfully used in Russia, provided that the Russian Government adopted Western-type measures of financial incentives.

The purpose of this work is to describe and review the current status of the recycling technologies of spent NiMH batteries. In the first part of the work, the structure and characterization of NiMH accumulators are introduced followed by the description of the main scientific studies and the industrial processes. Various recycling routes including physical, pyrometallurgical and hydrometallurgical ones are discussed. The hydrometallurgical methods for the recovery of base metals and rare earths are mainly developed on the laboratory and pilot scale. The operating industrial methods are pyrometallurgical ones and are efficient only on the recovery of certain components of spent batteries. In particular fraction rich in nickel and other materials are recovered; instead the rare earths are lost in the slag and must be further refined by hydrometallurgical process to recover them. Considering the actual legislation regarding the disposal of spent batteries and the preservation of raw materials issues, implementations on laboratory scale and plant optimization studies should be conducted in order to overcome the industrial problems of the scale up for the hydrometallurgical processes.

The literature is rich of scientific works regarding the recovery of yttrium and europium from red phosphors of lamps and it is poor of papers about the extraction of terbium, cerium and lanthanum from green phosphors. The red phosphors are constituted by rare earth oxides and they are more easily dissolved in the leaching step respect to the green phosphors that are rare earth phosphates. This paper was mainly focused on the recovery of rare earths from green phosphors, with major attention on terbium extraction that is the most valuable metal. Hence, an innovative process with a thermal pretreatment was proposed. Alkaline fusion with barium hydroxide and the following leaching were studied under various experimental conditions to optimize the process parameters. Statistical design of experiments and analysis of variance were performed in order to determine the main effects and interactions between the investigated factors (barium hydroxide/powders ratio, sulfuric acid concentration, leaching temperature, pulp density and leaching time) for the dissolution of each rare earth elements. The results, for most of REE considered, especially for terbium showed that barium hydroxide/powder ratio and temperature were significant with a positive effect. Concentration of sulfuric acid and pulp density were significant with a negative effect. Time of leaching instead had a very slightly positive effect. The best extraction yields, obtained under the optimal conditions, were: 99% for yttrium and europium, 80% for terbium, 65% for lanthanum, 63% for gadolinium and 60% for cerium. Therefore, rare earth oxides were produced after oxalic acid precipitation and calcination. The grade was 82.22% of yttrium oxide, 8.38% of europium oxide, 2.43% of cerium oxide, 2.29% of gadolinium oxide, 1.77% of lanthanum oxide and 1.52% of terbium oxide.

The present paper deals with an innovative scrubber (air pollution abatement) used to remove particulate matter and other pollutants from air. Air pollution abatement scrubbers were placed in different urban areas and in industrial production sites. In particular, the results obtained in one fiberglass production facility showed a reduction in particulate matter of 46.3–99.9% in the size range 0.50–0.00 µm throughout the experimentation period. The aqueous solutions coming from the scrubbers, placed in different sites, were collected, analyzed and treated in order to regenerate the water and make it available for the periodic refilling of the scrubber’s tanks. Coagulation, precipitation, carbon adsorption and Fenton processes were applied in order to design a suitable integrated process able to treat all the samples coming from the scrubbers. The reduction in total suspended solids, total dissolved solids, phenols and chemical oxygen demand was higher than 85% by the Fenton process, demonstrating that water is completely recoverable and reusable. Alternatively, the treated water can be discharged into a surface water body. Based on the results from the experimental campaign, a mobile plant was designed in order to treat such wastewater. Depending on the physicochemical parameters of the wastewater, specific treatments can be chosen and carried out by such mobile plant.

Waste of Electrical and Electronic Equipment (WEEE) is the fastest growing waste stream in Europe. This waste contains a high amount of critical and valuable metals as the rare earths defined critical materials from European Commission (2010) and the precious metals. Exhaust fluorescent lamps are examples of electronic wastes that have important percentages of rare earths elements (REEs). These types of WEEE represent an important secondary source of REEs. Moreover, they are classified as hazardous materials for the presence of mercury and need to be properly handled. Among the most valuable component of WEE there are printed circuit boards (PCBs) for their precious metals content. In the present paper a hydrometallurgical process for the recovery of REEs (yttrium, europium, terbium, gadolinium, lanthanum and cerium) from fluorescent powders and copper, tin, zinc, gold and silver from WPCBs. Hydrometallurgical process for rare earths recovery includes a preliminary roasting, acid dissolution and precipitation of a mixture of REEs oxalates. Alternately, a solvent extraction operation and stripping can be added after dissolution to selective recover rare earths. For the WPCBs treatment, a hydrometallurgical process consisting of two sequential leaching procedures (performed in counter and cross current ways) followed by selective precipitation/reduction of elements of interest from solution has been designed.

The present paper describes the experimental tests for the recycling of fluid catalytic cracking catalysts (FCCCs). The process aims at the recovery of cerium (Ce) and lanthanum (La) as well as the reuse of the leaching solid residue that represents the actual problem in terms of global amount landfilled every year. Landfilling is still the main choice for the handling of such catalysts. This novel process proposes an alternative recycling approach that leads to the production of synthetic zeolites, that have several industrial applications. FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80 °C, for 2 h with a solid to liquid ratio of 20 %wt, and the two rare earth elements were recovered by precipitation with an overall yield in the range 70–80%. The solid residues from the leaching stage were used as the base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62% and 97 %vol as purity. Since the results in adsorption of CO2 were not satisfying, the same zeolites were used to remove heavy metals from a synthetic wastewater solution containing three metals. Equilibrium and kinetic models were also developed in order to describe the adsorption process. The maximum adsorption load was calculated by the Langmuir isotherm and resulted to be 24–32 mg/g for Ni, 52–60 mg/g for Zn and 122–181 mg/g for Cu. The results also showed that the kinetics of the adsorption process is almost fast, as after 1 h at least 95% of zinc and copper were removed, whereas the kinetics of nickel was slower for all the three zeolites. As a conclusion, the zeolites are more efficient in metal adsorption than CO2 capture, but other applications will be tested in the future.

Aerobic degradation of effluents contains tetramethylammonium hydroxide molecules (TMAH), coming from an electronic industry, were studied at laboratory and pilot scale. At the first, the preliminary experiments were conducted using a lab scale reactor inoculated with activated sludge coming from urban wastewater treatment. Several batches have been performed on real effluent, in which TMAH concentration was about 1800 mg/L. The results showed that after acclimation, the microorganisms removed 99% of TMAH in seven days. Kinetic studies have provided the following kinetic parameters able to describe the trends of TMAH, ammonium ions and biomass concentration as a function of time in the reactor: KS = 0.8 g/L; µmax = 0.042 h-1. Then, in a second phase the experiments were conducted at pilot scale using a pilot plant realized within Life Bitmpas project (LIFE15 ENV/IT/000332). The plant has three biological reactors of 1 m3 and it is possible to feed up to 25 L/h of TMAH effluent. The experiments were conducted in a continuous mode and the results showed that in 8 days the total degradation of TMAH was 99%; moreover, from kinetic study have been determined the following kinetic parameters: Ks = 0. 83 g/L and µmax = 0.0074 h-1.

This study uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) to compare three process design alternatives for treating wastewater from galvanic industry. The proposed processes have been developed in according to a zero-liquid discharge, ZLD, approach and included reverse osmosis for the concentration, evaporation and crystallization of salts, mainly calcium chloride. The various scenarios differ for the type of utilities used for the operation (steam and as alternative hot water from thermal waste) and from an optimization of the crystallization step that provided an energy recovery from distillate. Results show that by using thermal waste as utilities for the operation of evaporation, crystallization and the optimization of crystallization unit is the most environmentally and economically favourable alternative.

Heavy metal pollution of civil and industrial wastewaters represents a major problem for the environment since metal ions are non-biodegradable, have a very high toxicity, and some of them have proved to be carcinogenic. If directly discharged in sewers, metal ions may seriously damage the subsequent biological treatments in depuration plants and render treatment sludge not reusable for agriculture. On the contrary, water and sludge reuse should be a primary criterion when planning improvements for wastewater treatment plants and their adaptation to new standards. In this paper, the membrane performance (a monotubular ceramic membrane of molecular weight cutoff: 210 kDa) is investigated in the removal of nickel and cobalt ions from synthetic liquid wastes aimed at water reuse using a micellar-enhanced ultrafiltration process. The ultrafiltration membrane is used with adding an anionic surfactant (sodium dodecyl sulfate (SDS)) in a laboratory scale experimental device. The synthetic liquid waste co...

The purpose of this chapter is to summarize the current status of the recycling technologies for the recovery of rare earths (i.e., yttrium, europium, terbium, lanthanum, and cerium) from spent fluorescent lamps, cathode ray rubes, and exhausted catalysts. The uses of these elements, especially for high-tech devices are increased in the recent years and combined with the scarcity of the primary sources and the environmental impact of the technologies to extract them from ores make the recycling waste a priority. For each type of waste this chapter contains a description of the most relevant scientific works and industrial application for the treatment of the waste at the end of their life. In the second part the recycling processes developed within HydroWEEE projects (grant number 231962; 308549) were presented. From the literature analysis, it was observed that many papers were published for spent fluorescent lamps treatment, fewer studies were found for the recycling of cathode ray tubes and spent FCC catalysts. This can be explained by considering the different intrinsic economic value, infact the fluorescent lamps contain high concentration of rare earths with high value (as yttrium, europium, and terbium), instead the other types of waste have a lower concentration of rare earths that also have less economic value.

This paper presents the upgrading of a full-scale domestic wastewater treatment plant, operating in Southern Italy, modified so as to process domestic wastewaters (WW) together with liquid wastes (LW), such as leachate and digestate in an integrated manner. The two streams - domestic wastewaters and liquid wastes - are separately pre-treated and then sent into a conventional denitrification/nitrification section. The preliminary treatments consist in grinding for WW and in grinding, flocculation, biological pre-treatment and advanced oxidation (Fenton process) for LW. Several scenarios were analysed using a process simulator (SuperPro Designer®): the concentrations of the main parameters (BOD5, COD, NH4+, NO3-, metals, SST) of the effluents were estimated as a function of BOD5/COD ratio, initial leachate volume and nitrate percentage in the recycle stream. In each case study the parameter values were compared with the regulatory limits provided for by the Italian Legislative Decree n. 152/2006 for discharge in surface water bodies. The results obtained show the intervals of variation of the main process parameters that in some cases do not permit to achieve the established limits.

The paper is focused on the application of solvent extraction for the recovery of rare earth elements from sulfuric leaching solutions obtained by the dissolution of fluorescent powders of lamps. The efficiency on rare earths extractions of three extractants, Cyanex 272, Cyanex 572 and D2EHPA in kerosene were investigated as a function of pH levels. Similar extraction for all the rare earths elements were observed, but the tests performed with D2EHPA showed that for pH values less than 1, yttrium and terbium could be extracted with yields higher than the other rare earths. The orders of the extraction were determined: yttrium ≥ terbium > gadolinium ≥ europium > cerium ≥ lanthanum. Further tests showed the optimal conditions, under the investigated ones, to extract yttrium with traces of terbium and cerium from sulfate leaching solutions. According to the experimental results, operating conditions of extractions were proposed in order to establish the guidelines for the following stripping and operation steps to recover rare earths selectively or at least in groups of them. A simulation of the proposed process was performed using a specific software in order to define the mass and energy balance of the entire recycling treatment of spent lamps. © 2017 Elsevier Ltd

The aim of this research was to investigate the methyl orange degradation using hydrodynamic cavitation. The synthetic solutions simulated a real textile effluent containing dye and metals (iron and nickel) as a consequence of the corrosion of nickel-plated metal components of the plant during the production of textile materials. In the first series of experiments, the hydrodynamic cavitation was studied in terms of operating inlet pressure and pH of solution. Subsequently, a full factorial plan was performed to determine the main effects and interactions among the investigated factors: inlet pressure (pin), temperature (T), initial dye concentration (cMO/0), and treatment time (t). The results showed that inlet pressure, temperature and concentration had a significant positive effect on dye degradation, as well as the interactions temperature/dye concentration and pressure/time. The optimum operating conditions among those investigated were: cMO/0 = 5 ppm, pH = 2, pin = 0.6 MPa and t = 1 h, independently of temperature (T). In the above conditions, the degradation yields were near to 75% and the final concentration was less than 1 ppm. On the contrary, at cMO/0 = 20 ppm, pH = 2, pin = 0.6 MPa, T = 40 °C and t = 1 h, the degradation efficiency was about 56% and the final concentration was less than 9 ppm. A comparison among the experiments carried out in the absence and in the presence of iron and nickel showed that metals acted as catalysts and the energy required for the process with metal ions was 5 times smaller than that those required by the experiments conducted without the metals in solution, at the same operating conditions.

In 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.

In this paper, the efficiency of micellar enhanced ultrafiltration technique (MEUF) was tested for the removal of yttrium and zinc ions from synthetic industrial liquid wastes. UF membranes (monotubular ceramic membranes of 210 kDa and 1 kDa molecular weight cut-off) were used with adding an anionic surfactant, sodium dodecyl sulfate (SDS). A two - level full factorial design was performed in order to evaluate the effect of molecular weight cut-off, sodium dodecyl sulfate concentration and pressure on the permeate flux and rejection yields. It was found that the single factors presented the largest influence on the permeate flux: the membrane pore size and the pressure had positive effect, instead the SDS had negative effect. Regarding the metal rejection yields the main relevant factors were the membrane pore size with a negative effect, followed by the surfactant concentration with a positive effect. The effect of the pressure seemed to be almost negligible, for zinc removal experiments had a positive effect in the interactions with the surfactant and membrane pore size. The results showed that very good removal percentages up to 99% were achieved for both metals under the following conditions: 1 kDa membrane MWCO, in the presence of the surfactant at a concentration above CMC independently of the investigated pressure.

Hydrometallurgical processes for the treatment and recovery of metals from waste electrical and electronic equipment produce wastewaters containing heavy metals. These residual solutions cannot be discharged into the sewer without an appropriate treatment. Specific wastewater treatments integrated with the hydrometallurgical processes ensure a sustainable recycling loops of the electrical wastes to maximize the metals recovery and minimize the amount of wastes and wastewaters produced. In this research activity the efficiency of ultrafiltration combined with surfactant micelles (micellar-enhanced ultrafiltration) was tested to remove metals form leach liquors obtained after leaching of NiMH spent batteries. In the micellar-enhanced ultrafiltration, a surfactant is added into the aqueous stream containing contaminants or solute above its critical micelle concentration. When the surfactant concentration exceeding this critical value, the surfactant monomers will assemble and aggregate to form micelles having diameter larger than the pore diameter of ultrafiltration membrane. Micelles containing contaminants whose diameter is larger than membrane pore size will be rejected during ultrafiltration process, leaving only water, unsolubilized contaminants and surfactant monomers in permeate stream. The experiments are carried out in a lab-scale plant, where a tubular ceramic ultrafiltration membrane is used with adding a surfactant to concentrate heavy metals in the retentate stream, producing a permeate of purified water that can be reused inside the process, thus minimizing the fresh water consumption.

The paper is focused on the study of hydrometallurgical processes for recovery of rare earths (RE) from fluid catalytic cracking catalysts (FCCC). According to the experimental results two processes were proposed: in the first one RE were recovered as double sulfates by selective precipitation with sodium hydroxide after leaching with sulfuric acid. The second approach consisted of dissolution of powder by acids, solvent extraction by (2-ethylhexyl)phosphoric acid (D2EHPA), stripping and precipitation of RE oxalates using oxalic acid. Experiments showed that solvent extraction was found to be beneficial in terms of achieving improved final products quality with greater purity (∼98%).