Crystal Growth In Solid Phase Based On The Agglomerationg Method

In this paper,a new way to grow crystals in solid phase based on the fertilizer granulation had been reported.Humic acid and mushroom residue was used as raw material,gypsum was choosed as binder,as well as grinding and granulating process under the addition of the other raw materials and solvent.After a period of time,the crystal was grown on the particle surface.Humic acid,mushroom residue provided the environment for crystal growth,gypsum made the raw material closely,the volatilization of solvent promoted the growth of crystals in the solid phase,the grinding process resulted in physical or chemical reaction between solid materials.First of all,colorless and acicular urea crystal was got on the fertilizer particles formed by mushroom residue,humic acid,sodium dihydrogen phosphate,urea and gypsum,the unit cell parameters were a = 5.6427 ?,b = 5.6427 ?,c = 4.7168 ?,? = 90°,? = 90°,? = 90°.Furtherly,reasons for the formation of crystals were analyzed,and the effects of water and particle size on the crystal growth were discussed.It was found that humic acid,mushroom residue as a growth environment provided channels for crystal growth because of loose and porous structure,and the volatilization of solvent provided traction for the crystal growth,these factors contributed to the crystal growth.In addition,when the water was suitable,the fertilizer particle was bigger and regular,and the crystal was longer.Crystal growth on the 4-5mm particles was good.Secondly,ammonium sulfate crystal was got on the fertilizer particles prepared by humic acid,gypsum,ammonium fluoride and urea through the indirect solid phase growth method.The lattice parameters were a = 7.7814 ?,b = 5.9936 ?,c = 10.6484 ?,? = 90°,? = 90°,? = 90°.The cause of the formation of ammonium sulfate crystal in the solid phase and the growth of the crystal were analyzed.It was found that the formation of ammonium sulfate crystals was due to a chemical reaction between the raw materials calcium sulfate and ammonium fluoride,which produced ammonium sulfate and calcium fluoride.The loose structure of humic acid and the rigid rod structure of c alcium sulfate formed a honeycomb channel,which was the basis of crystal growth.In the granulation process,the mechanical pressure produced by extrusion between material s became the driving force of crystal growth.In addition,the solid environment in middle and lower sample bags were more stable and slow water-evaporating,with higher quality crystal than upper.In the end,without the direct supply of urea and ammonium chloride,acicular urea-ammonium chloride crystal was got on the fertilizer particles formed by humic acid,ammonium thiocyanate,ammonium sulfate,urea,potassium chloride,ammonium phosphate and gypsum through indirect solid state method,the cell parameters were a = 7.9177 ?,b = 17.1305 ?,c = 8.0557 ?,? = 90°,? = 90°,? = 90°,and its properties were determined.Ammonium ions provided by ammonium sulfate and ammonium thiocyanate,chloride ion in potassium chloride,and urea molecules formed urea-ammonium chloride molecules together.When the molar ratio of ammonium thiocyanate to urea was 1:5,the crystal of urea ammonium chloride could be obtained.In conclusion,on the basis of the granulation process,crystals of urea,ammonium sulfate and urea-ammonium chloride were obtained by direct and indirect solid phase growth respectively.The reasons for the formation of the crystal after the addition of different raw materials,the effect of some conditions on the crystal growth and the importance of humic acid and calcium sulfate in crystal growth were discussed respectively.Through the study of growth mechanism in solid phase,it was helpful for the synthesis of other crystals by solid growth technology,and to improve the theoretical system of the method at the same time.