It is a main problem that environment can be polluted by discharge of wastewater containing NH4+, Ca2+ and Na+, when rare earths (REs) are extracted in a saponified system using di-(2-ethylhexyl) phosphoric acid (D2EHPA). Pointing to this problem, the selective separation of Pr(Ⅲ) by liquid–liquid extraction using D2EHPA in the presence of a complexing agent of lactic acid (LA) has been studied. Results are shown that the maximum of separation factor (β) between Pr/Ce is 2.04 and extraction selectivity is also enhanced when compared with that of D2EHPA–HCl system. The thermodynamic function △H is determined as exothermically driven. The cation exchange mechanism is discussed by IR spectra. Thus, the results suggest that highly selective separation and extraction of Pr(Ⅲ) from a Pr/Ce solution is possible, providing a simple and environment-friendly complexing method for extraction-separation rare earths, and promoting the sustainable development in rare earths practices.of Pr(Ⅲ) from a Pr/Ce solution is possible, providing a simple and environment-friendly complexing method for extraction-separation rare earths, and promoting the sustainable development in rare earths practices.

Nowadays, people should pay more attention on the environment problems that had advent along with the development of rare earth metallurgy industry. A large number of water pollutant, air pollutant and solid pollutant were discharged in the process of synthesis of rare earth compound by precipitation and roasting process. In order to solve the industry pollution problems, a new technology route was developed for the preparation of lanthanum oxide using lanthanum chloride as raw material by oxy-hydrogen flame route. The experiment results showed that lanthanum chloride could directly convert to lanthanum oxide under high temperature by the combustion of mixture gas of hydrogen-oxygen that provided by oxy-hydrogen generator continuously. The phase composition of obtained product was characterized by XRD and the conversion rate of lanthanum chloride and the reaction mechanism were discussed.

Bastnaesite was activated at a temperature, and then the rare earths carbonate of the minerals was leached by HCl solution. When activation temperature was 400°C, activation time was 3h, HCl concentration was 3 mol•L-1, leaching temperature was 90°C, liquid to solid was 20:1, the leaching ratio of rare earths carbonate and rare earths fluoride was 94.6% and 0.07% respectively. The results of XRD and SEM showed that bastnaesite was powdered and coarseness in activation process, which made the leaching of rare earths carbonate by HCl solution become easy. The main components of leaching slag were rare earths fluoride, calcium fluoride and barium sulfate.

With lanthanum chloride solution as raw material, and use the hydrogen peroxide of clean and pollution-freeobtained from oxidation reaction as auxiliary reagent, and with the carrier gas together form spray pyrolysis to obtain lanthanum oxide. On the one hand, in the hydrogen peroxide system, the temperature of direct pyrolysis reaction of lanthanum chloride solution decreased obviously, The reaction temperature is decreased from 1280°C to 1000°C or less. That reduce the energy consumption and simplify the requirements of pyrolysis equipment technology. The production process does not use NH3.H2O and NaOH to precipitate. It does not produce the traditional process of NH4+, Na+ to pollute water. It can greatly reduce the damage to the environment, and can product with high yield, high purity of the rare earth oxide. This method not only applies to the pyrolysis of the rare earth chloride solution, also applies to metal chloride solution, such as FeCl3, AlCl3, NiCl2. It was shown that the reaction temperature has been effectively reduced, VLaCl3: VH2O2 with 1: 1.5 can get high purity of La2O3.

Bastnaesite was activated at low temperature, and the results of XRD, SEM and Raman showed that the particle size of minerals increased firstly, and then decreased with increasing of temperature. The polarization of rare earths fluoride decreased in activation minerals. Using HCl leaching, the rare earths carbonate and rare earths fluoride were separated effectively, and 94.6% rare earths carbonate and only 0.07% rare earths fluoride was dissolved respectively. The results supplied a new method of bastnaesite decomposition.