ABSTRACT
Due to the complex composition of ion-adsorbed type rare earth ore leaching solution, there are challenges in the process of rare earth (RE) separation, such as large RE loss rate, low product purity, radioactive residue and so on. In this article, 8-hydroxyquinoline modified silica gel (HQ-SiO2) and 2,2'-(1,4-phenylenebis(oxy)) dioctanoic acid (PPBOA) were used to form an efficient process for impurities removal and RE enrichment. Solid phase extraction successfully intercepted 96.7% of the radioactive element thorium. The concentration of aluminium was reduced to 2.14 ppm by frank chromatography. Rare earth elements were enriched from 336.35 mg/L to 237.75 g/L by extraction-precipitation, that is, the enrichment multiple reached more than 700 and the proportion of RE was increased from 21.85% to 96.62%. The loss rate of RE was controlled below 1.59%. Moreover, the magnesium salt leaching solution could be recycled for the leaching of RE ores. Although some liquid waste need to be treated in the processes of HQ-SiO2 production and regeneration, the integrated process helps to decrease volatile organic solvent, acid-base consumption, wastewater and waste residue. It is an environment-friendly RE enrichment and impurity removal process, which shows application potential in the production field of ion-adsorbed type rare earth mineral products.
Subject(s)
Magnesium , Metals, Rare Earth , Metals, Rare Earth/analysis , Minerals , Recycling/methods , Silicon DioxideABSTRACT
A novel method for the selective removal and recovery of copper ion from copper-containing wastewater by extraction-precipitation with p-tert-octyl phenoxy acetic acid as a precipitant is presented. The morphology, thermal stability and solubility of POAA were synthesized and characterized. Then the application of POAA to precipitate copper from simulated copper-containing wastewater was studied. The effects of some factors (i.e., time, pH, temperature, dosage of precipitant) on copper precipitation efficiency (P%) and water solubility of POAA were discussed. The extraction-precipitation mechanism of POAA and Cu2+ was investigated by slope analysis combined with SEM, EDS, XPS and IR spectra. The concentration and purity of copper from industrial wastewater increased from 100.2 mg/L to 27,916 mg/L and 13.71%-93.01% respectively, treating by the proposed extraction-precipitation. Moreover, POAA revealed good stability in the recycling processes. Extraction-precipitation strategy is simple, efficient and sustainable, which can effectively reduce the volume of sludge in the process of wastewater treatment and produce copper concentrated solution with industrial value, which has revealed application potential for the clean production of copper smelting enterprises.
Subject(s)
Wastewater , Water Purification , Acetic Acid , Copper/analysis , Hydrogen-Ion ConcentrationABSTRACT
Due to its poor water solubility, the herbicide cyanazine is usually dissolved in organic reagents when used, which poses a great threat to the environment. Poor water solubility also causes limited herbicidal activity. In our study, the water solubility of cyanazine was increased by forming a cyanazine/hydroxypropyl beta-cyclodextrin (HPßCD) inclusion complex. The formation of the inclusion complex was confirmed by FT-IR, XRD, SEM and other characterization methods. Phase solubility study showed that HPßCD could improve the water solubility of cyanazine. Thermogravimetric analysis indicated that the thermal stability of cyanazine was improved by forming inclusion complex and the biological activity test showed that better herbicidal activity was obtained on the inclusion complex compared with the cyanazine. The results showed that the formation of inclusion complex could improve the application of cyanazine in agricultural production and reduce the risk to the environment.
ABSTRACT
In this study, hydroxypropyl-ß-cyclodextrin (HPßCD) was used to form an inclusion complex with fluroxypyr to enhance water solubility and thermal stability. The inclusion complex was prepared by a saturated solution method and characterized by FT-IR, SEM, TGA, and XRD. All results indicated that fluroxypyr successfully entered the HPßCD cavity. In addition, the study of phase solubility identifies that the water solubility of fluroxypyr was greatly improved after the formation of the inclusion complex, and TGA analysis suggested that the formation of the inclusion complex improved the thermal stability. Bioactivity assay tests showed that the inclusion complex still had strong herbicidal activity. Our research showed that HPßCD was a promising carrier for improving the properties of fluroxypyr and, thus, expanding its use in agrochemical formulations.
