Performanee Study On Highly Reactive Thiourea Dioxide Made By Rare Earth

Thiourea dioxide(also called TD) is widespread used in various fields because its good characteristics of slow decomposition、safe、convenient and high reduction potential. The theory of potential value of TD is -1200mv, at the normal temperature or under the condition of acid TD is very stable, only in strong alkali (pH>10) and heat condition (> 70℃) can show the strong reduction performance.It make TD has limitations in the aspect of application.This experiment use homemade rare earth oxides and rare earth organic complexes as catalyst, through a series of experiments,we explored an effective means of catalytic activation, make thiourea dioxide exhibit high reduction potential under the conditions of room temperature (25℃) and weakly alkaline (pH=8). The specific research:(1) TD will not show a strong reduction performance under mild condition,but it can get it when at strong base and heat condition.By control condition we find the temperature and pH is higher the reduction performance of TD is stronger. The reduction potential of TD will up to-895mv and can be maintained for a long time at above -850mv.(2) Activation of thiourea dioxide by homemade rare earth oxides:the activation effect of cerium oxide is best when after contrast experiment effect. The reduction potential rose rapidly when cerium oxide accounted for 3% of the mass of TD. Under the mild condition, the reduction potential can be stabilized at about -729mv and can be maintained for a long time at above -720mv.(3) The best condition of activating TD by homemade rare earth cerium single ligand complex:use the PHBA as ligand、the pH value of reaction system is 9、the reaction time is 60min、in the process of the reaction the mole ratio between cerium chloride and PHBA is 0.6. Use the complex under this reaction condition to activating TD, the reduction potential can be stabilized at about -789mv and can be maintained for a long time at above -780mv.(4) The best condition of activating TD by homemade rare earth cerium double ligand complexes:use the PHBA as the first ligand、 1,10-Phenanthroline as the second ligand、the pH value of reaction system is 9、the reaction time is 60minin the process of the reaction the mole ratio with cerium chloride、PHBA and phen is 1:2:1. Use the complex under this reaction condition to activating TD, the reduction potential can be stabilized at about -848mv and can be maintained for a long time at above -835mv. Approximately reached the reduction potential of TD solution at temperature of 85℃, pH=12. The activation effect is remarkable.(5) The experiment of Kaolin whitening by activation TD:By controlling the dosage of TD,it is concluded that the best solution of activation TD bleach Kaolin:when the amount of thiourea dioxide, accounted for 0.5% of kaolin, the whitening effect is best,whiteness is 88.7%(Initial whiteness is 82.6%; the whiteness up to 84.3% after bleached by hydrosulfite). The addition to iron effect is remarkable.(6) Through contrasting the XRD between the undressed ore of Kaolin and the concentrate after bleaching,we find the diffraction peak of hematite impurities has a clear decline,it means the content of iron impurity decreased significantly; comparison and analysis by SEM,we can find the coloring matter at Kaolinite boundary and the surface has decreased significantly after reduction bleaching prccess by TD, The surface of the kaolinite is very pure,that means in the run of mine ore,most of the contain iron content has been removed, the addition to iron effect is remarkable.