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Study On Preparing Bismuth Products Such As Bismuth Subcarbonate By Liquid Ball-milling Transformation Method From Bismuth Oxide

Posted on:2014-04-23Degree:MasterType:Thesis
Country:ChinaCandidate:Y JiangFull Text:PDF
GTID:2251330425472389Subject:Metallurgical engineering
Abstract/Summary:PDF Full Text Request
Bismuth subcarbonate and bismuth subnitrate, the deep-processing products of bismuth, are widely employed in research and development for medicine field. The existing preparation of bismuth subcarbonate and bismuth subnitrate is on the basis of preparation of bismuth nitrate first. So the problems of producing toxic NO2and ammonia-nitrogen waste water are inevitable. Dealing with these hazardous wastes can lead to high production costs, complex work-flow and environmental pollution. A new process for preparation of bismuth subcarbonate and bismuth subnitrate by ball-milling transformation method from bismuth oxide has been proposed to solve those above problems. Compared with traditional method, this new process has many merits such as short procedure, inexpensive reactant and low cost. One of the greatest strengths is that mother liquid can be utilized circularly and there is no poisonous gases or ammonia-nitrogen waste any more. This new process is worthy of further research and industrial application. Effect of reaction temperature particle size of bismuth oxide, liquid-solid ratio and different concentrations of ammonium bicarbonate on the conversion rate of bismuth oxide has been investigated, respectively. The results indicate that higher temperature, smaller particle size, higher concentration of ammonium bicarbonate and larger liquid-solid ratio are favorable to accelerate the conversion rate of bismuth oxide. Kinetic studies demonstrate that bismuth oxide ball-milling transformation follows unreacted shring core model, and the whole transformation process is controlled solid product layer interior diffusion mechanism.The dynamic equation as following is also fitted to describe the transformation process:1-2/3R-(1-R)2/3=0.553×10-3×CNH4HCO30.837×D-0.128×(S/L)-0.209×exp(-9.783/RT) Then, the process of preparation of bismuth subcarbonate by ball-milling transformation is investigated by using orthogonal and single factor experiment methods. The orthogonal experiment results show that the liquid-solid ratio, the weight ratio of ball to bismuth oxide, ball-milling time and ammonium bicarbonate concentration have an effect on the conversion rate of bismuth oxide. The single factor experiment results show that the optimum conditions for ball-milling process are determined as follows:the concentration of ammonium bicarbonate is2.5mol/L, the ratio of liquid to solid is7:1, the weight ratio of ball to bismuth oxide is8:1and the ball-milling time is2h. The conversion rate of bismuth oxide can be up to91.92%under these conditions. The results of TEM show that the bismuth subcarbonate products are patchy in distribution.In the end, the process of preparation of bismuth subnitrate by ball-milling transformation is investigated by using orthogonal and single factor experiment methods. The orthogonal experiment results show that the liquid-solid ratio, the weight ratio of ball to bismuth oxide, ball-milling time and the concentration of nitric acid have an effect on the conversion rate of bismuth oxide. The single factor experiment results show that the optimum conditions for ball-milling process are determined as follows:the concentration of nitric acid is0.5mol/L, the ratio of liquid to solid is15:1, the weight ratio of ball to bismuth oxide is10:1and the ball-milling time is1h. The conversion rate of bismuth oxide can be up to90.71%under these conditions. The results of TEM of the bismuth subnitrate products show rod-like structure.There are32figures,27tables and105references in this paper.
Keywords/Search Tags:bismuth oxide, ball-milling transformation, bismuthsubcarbonate, bismuth subnitrate, kinetic studie
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