Until now, rare earth elements (REEs) recycled from the green phosphor of waste fluorescent lamps (FLs), essentially terbium, remain a major challenge. The sulfuric acid effect on leaching efficiency ...of REEs from phosphor powder (PP) is investigated in this paper. According to a composite central design, experimental leaching study is performed under various parameters (acid concentration, leaching temperature, and time as well as liquid-to-solid ratio (L/S)). A statistical model of experiments and an analysis of variance are studied in order to predict leaching process. The results showed that by decreasing concentration and L/S ratio while increasing leaching time at optimal temperature value permits profitable terbium extraction. Afterwards, the developed statistical model is explored for an optimized response surface methodology. The obtained results were tested experimentally and showed best terbium extraction with 75%. Moreover, 0.01% for the major contaminant, that is calcium, is reached. This low calcium yield may have a further advantage during REE recovery in the downstream. Therefore, resulting solution under optimal conditions is treated with oxalic acid followed by a calcination of the solid precipitate. Finally, 43.57% and 49.38% are produced for terbium and yttrium oxides, respectively.
Tannic acid is a calcite flotation agent widely used in mineral processing. To better understand the physicochemical reactivity of tannic acid toward calcite, the present work focused on studying the ...mechanisms involved during the adsorption process. Hence, in order to determine the optimal physicochemical parameters, tannic acid adsorption onto calcite was investigated at various experimental conditions such as contact time, initial tannic acid concentration, solution pH, particle size, and temperature. The obtained results showed that the adsorption capacity of tannic acid increased significantly with initial tannic acid concentration. Furthermore, tannic acid adsorption onto calcite was highly dependent on solution pH, and the optimal adsorption amount was found to be at pH 8. Therefore, the behavior controlling the studied adsorption process could be attributed to ion exchange. Moreover, the adsorption mechanism has been determined by isothermal, kinetic, and thermodynamic studies. Thus, the Sips isotherm model was the one that best predicted equilibrium data. Adsorption kinetics followed a pseudo-second-order model, indicating that the adsorption process was controlled by the chemical reaction. The estimated thermodynamic parameters revealed that the adsorption reaction was exothermic in nature and the system entropy decreased nonsignificantly during this process. Based on these results, the study of the physicochemical interaction between tannins and carbonates has potential application in mineral processing as well as in other fields.
In the process of desalination by indirect freezing, ice formed on the cooled surface contains impurities due to kinetic effects. Sweating is an efficient method by which ice layer is purified under ...the effect of temperature gradient. The main kinetic parameters influencing sweating of ice are initial concentration of ice, sweating temperature and sweating time. In the present work, the effects of these parameters were studied using an experimental design. A statistical model for ice weight and ice purity was developed. The graphical representation of this model in the space of the variables enabled optimization of the whole desalination process time, which led to ice salinity less than the drinking water standards (0.5g/kg).
►Layer melt crystallization was applied to seawater desalination. ►The process involves two consecutives steps: freezing and sweating. ►Sweating has enabled the obtention of ice with low salt concentration, satisfying standards of potability. ►Optimal operating conditions are proposed by means of an experimental design.
This work reports a synthesized natural Moroccan hydroxyapatite (NHAP) phosphors doped by rare-earth elements using ion exchange technique. The objective of this technique lies in the generation of ...luminescence after UV excitation of the synthetized phosphors. Effects of doping and co-doping on the NHAP physicochemical properties were investigated using multiple characterization methods such as X-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared spectroscopy, inductively coupled plasma and photoluminescence spectroscopy. The XRD results show that Tb
3+
/La
3+
incorporated into NHAP does not change its structure. Under near-ultraviolet excitation at 405 nm, NHAP:
x
Tb
3+
,
y
La
3+
samples show the advantage to obtain a single emission peak, which corresponds to the green colour characteristic of terbium. Moreover, the chromaticity coordinates of NHAP: 0.5%Tb, 1.5%La indicate the excellent cool green-emitting phosphors with a low correlated colour temperature. Overall, the obtained results suggest that NHAP (0.5%Tb: 1.5%La) could be used as multifunctional bio-imaging materials or solid-state lighting for LEDs with high lighting efficiency.
Graphical abstract
This work aims at developing a dynamic layer crystallizer operated batchwise, for freezing desalination of sea water. The experiments were performed with water/NaCl solutions and with samples of sea ...water from Nice, Rabat and Marseille. The pilot crystallizer consists of a cooled tube immersed in a cylindrical double jacketed tank. The solution is poured into the tank and the crystallization takes place on the external surface of the tube, by applying a cooling ramp in the tube. The solution is agitated by air bubbling. The whole process involves the freezing step, leading to the crystallization of the ice layer and the sweating step, which consists of purifying in depth the ice layer by melting the impure zones. A parametric study on the effect of the operating parameters has allowed quantifying the role of the different key parameters of the freezing and sweating steps. Three experiments allowed reaching salinities lower than 0.5g/kg, satisfying the standards of drinking water. The duration of the whole process dropped to only 8h (5h for freezing and 3h for sweating), with a yield of sweating equal to about 50%, provided severe conditions were applied for sweating. Higher yields required longer times. Overall, the results show the feasibility of the technique.
► Initial temperature, ice growth rate and solution salinity are the parameters affecting ice purity. ► The sweating step is able to efficiently complete the purification. ► The duration of the whole process dropped to only 8h (5h for freezing and 3h for sweating).
Desalination of seawater can provide an almost inexhaustible source of freshwater if it can be made affordable. This work is part of an innovative approach aimed at improving the seawater ...desalination cost through the development of a new method which is more efficient than the existing processes in use. A benchmarking study and a literature analysis were realized, and the results helped us in orientating research study toward the development of an industrial hybrid system coupling freezing and reverse osmosis (RO). The freezing process is proposed as a method of seawater pre-treatment for the RO membranes. It is coupled with a heat pump system which freezes the seawater inside a crystallizer and melts the ice in a melting chamber. By combining freezing and membrane desalination processes, the hybrid system has been successfully improved. The evaluation of the proposed systems' energy consumption shows energy savings of approximately 25%, and an improvement of the quality of osmotic water for about 71% when compared to the conventional-RO desalination. This evaluation was conducted on the basis of mass and energy balances of the freezing process and simulation of the RO desalination process using a non-commercial software.
This study focuses on the optimization of a freeze crystallization process within a Scraped Surface Heat Exchanger (SSHE) using the response surface methodology (RSM). The process in question was ...developed and modeled in our previous work for a new hybrid seawater desalination system combining freezing for pretreatment and reverse osmosis 1, 2. The process simulation allowed predicting interpretable physically trends of the seawater crystallization main key phenomena within the SSHE such us the suspension temperature evolution and the ice volume fraction. The objective of this work is to determine all operating conditions that result in the best process performance. Response surface methodology with MINITAB software has been used to find the optimum design operating point of the proposed new freeze seawater desalination pretreatment process.
Weirs and spillways play crucial roles in hydraulic engineering, contributing significantly to sustainable water resource management. However, challenges remain in obtaining optimal design, safe ...management and enhanced performance of these structures. The remarkable breakthrough in artificial intelligence technology present promising options to address these challenges. This study aims to quantitively analyze the current state of the integration of artificial intelligence into the study of weirs and spillways, using a bibliometric analysis of documents available in the SCOPUS database through VOSviewer. The study unraveled interesting patterns within the research domain, emphasizing the application of artificial intelligence methods for optimizing the design of weirs and spillways. Furthermore, artificial intelligence has a role in enhancing physical and numerical hydraulic modelling. The integration of artificial intelligence in the exploration of weirs and spillways holds substantial promise for advancing the field of hydraulic structures.
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