Three commercial resins bearing sulfonic, amino phosphonic, or phosphonic/sulfonic reactive groups have been tested for the removal of iron and cadmium from phosphoric acid solutions. The sorption properties are compared for different experimental conditions such as sorbent dosage (0.5-2.5 g L −1), phosphoric acid concentration (from bi-component solutions, 0.25-2 M), and metal concentrations (i.e., in the range 0.27-2.7mmolCdL −1 and0.54mmolFe L −1) with a special attention paid to the impact of the type of reactive groups held on the resins. The sulfonic-based resin (MTC1600H) is more selective for Cd (against Fe), especially at high phosphoric acid concentration and low sorbent dosage, while MTS9500 (aminophosphonic resin) is more selective for Fe removal (regardless of acid concentration and sorbent dosage). Equilibrium is reached within 2-4 h. The resins can be ranked in terms of cumulative sorption capacities according the series: MTC1600H > MTS9570 > MTS 9500. Sulfuric acid (0.5-1 M) can be efficiently used for the desorption of both iron and cadmium for MTC1600H, while for MTS9570 (phosphonic/sulfonic resin) sulfuric acid correctly desorbs Cd (above 96% at 1 M concentration), contrary to Fe (less than 30%). The aminophosphonic resin shows much poorer efficiency in terms of desorption. The sulfonic resin (i.e., MTC1600H) shows much higher sorption capacity, better selectivity, comparable uptake kinetics (about 2 h equilibrium time), and better metal desorption ability (higher than 98% with 1 M acid concentration, regardless of the type of acid). This conclusion is confirmed by the comparison of removal properties in the treatment of different types of industrial phosphoric acid solutions (crude, and pre-treated H 3 PO 4 solutions). The three resins are inefficient for the treatment of crude phosphoric acid, and activated charcoal pre-treatment (MTC1600H reduced cadmium content by 77%). However, MTC1600H allows removing over 93% of Fe and Cd for H 3 PO 4 pre-treated by TBP solvent extraction, while the others show much lower efficiencies (< 53%).
The equilibrium and kinetic characteristics of rare earths adsorption process using the strong acid macro reticular resin Dowex 50X8 from El-Erediya chloride liqueurs have been determined. The adsorption parameters including pH, contact time, temperature, resin to aqueous ratio and rare earths initial concentration in aqueous have been optimized. The practical adsorption capacity of rare earths upon the resin under the optimum conditions has been found to attain 80 mg/g which matches with Langmuir theoretical capacity. The physical parameters including the adsorption kinetics, the isotherm models and the thermodynamic data have also been determined. The adsorption process has been found to agree with both the pseudo second order reaction, the Langmuir isotherm and confirms with the concept of the matrix diffusion controls. A successful preconcentration process for the rare earths content was done with a preconcentration factor of about 42.33. Considerable rare earths cake was precipitated from the chloride eluate solutions using oxalic acid.
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Rare earthsAmmonium hydroxide Uraniferous Hydrofluoric acid Oxalic acid a b s t r a c tThe study area of Gabal El Sela at Halaib environ is located at about 20 km west of Abu Ramad City, Egypt. An uraniferous ore material associated with REE was subjected to sulphuric acid leaching for the extraction of uranium mainly and REEs as a by-product.93.9% of U and 60% of REEs content were leached using À0.5 mm ground ore with 100 g/l sulfuric acid, acid/ore ratio of 2.0 and agitate for 6 h at 40 C. After uranium extraction, effluent solutions containing 135 ppm rare earths were treated with 30% ammonium hydroxide to pH of 9.3 to enhance the rare earth elements concentration. The precipitated cake was filtered then dried at 110 C. The dried cake containing 16.2% rare earth elements was dissolved by hydrochloric acid at pH 1.0. The rare earths precipitated cakes of 36.9, 45.7 and 48.7% REEs were recovered successfully from the chloride leach liquor of 900 ppm rare earths by using 5% v/v from 50% HF, 6% wt/v oxalic acid and 4.8% wt/v oxalic acid to chloride solution with heating for one hour which respectively. 73.5% REEs precipitated cake was achieved by double precipitation, firstly by hydrofluoric acid followed by oxalic acid precipitation.
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