Extraction Method Of Yellow Phosphorus In Poor Phosphorus Sludge

In the production of yellow phosphorus, it will inevitably produce large amounts of phosphorus sludge. The rich phosphorus sludge is used for extracting yellow phosphorus and the poor is not used properly because of the complex colloid structure. Most part of it is stored as hazardous wastes and used to produce phosphoric acid. The other part is used for producing fertilizer. It can not only improve the phosphorus resource utilization rate, but also get the better economic and environmental benefitsThis research focused on poor phosphorus sludge(P 10%~15%) and analysed the composition and structure of sludge by means of XRF(X Ray Fluorescence), XRD(X-Ray Diffraction) and microscope. Then we came up with the idea of using "hexane extraction + Ultraviolet spectrophotometric" to determinate phosphorus content in phosphorus sludge. We designed a small set of distilling phosphorus device and analysed the effect of temperature,time and other factors to distilling phosphorus from poor phosphorus sludge. At the same time, the pretreatment effect of the chemical method on poor phosphorus sludge was investigated. besides,the leaching experiment of the distillation residue was carried on. The results showed:XRF analysis shows that poor phosphorus sludge consists of SiO2(34.95%)、P2O5(24.89%)、F(18.20%)、K2O、CaO、Al2O3 and some other chemical composition and has O、F、Si、K、P(10.86%)、Ca、Al and some other elements.;XRD analysis showed that the main phases of poor phosphorus sludge was K2SiF6;Under the microscope, it is observed that the phosphorus was mainly existed in the shape of amorphous polymer which is in different sizes.Using "hexane extraction + ultraviolet spectrophotometric" to determinate phosphorus content in phosphorus sludge was highly efficient. Under the conditions of 2g phosphorus sludge, 20 mL hexane and 10 min of shaking,the amount of phosphorus can be fully extracted. Moreover, taking the chessboard type full layer sampling can well solve the problem that phosphorus uneven distributed in the two-dimensional space of sludge cake.The experiments show that temperature and time were the major factors for recovering phosphorus. Under the conditions which temperature was 270℃ to 300℃ and time was over 20 min,the recovery rate of phosphorus can achieve the above 80%. The time was shorter when the temperature was higher.The chemical method was applied to pretreatment of sludge samples and well improved the recovery rate of phosphorus as it destroyed the structure of colloid. The results revealed that when pretreatment agent was H2SO4, the dosage was 4 mL(1.2mol/L), the temperature was 60℃ and the time was 30 min, we got the best effect. Under the conditions that temperature was 280℃ and time was 15 min,the recovery rate of phosphorus was 53.86 % without pretreatment and the rate was 82.50 % with pretreatment.Meanwhile, leaching test results suggested that the residue will impact the environment. In the leach liquor of the residue with H2SO4 pretreatment, total phosphorus was 243.99 mg/L,phosphate was 203.07 mg/L and P was 8.82 mg/L. It is necessary that taking corresponding measures to have a stabilizing treatment on this sludge and to meet the requirement of general industrial solid wastes.This research made a beneficial exploration for effectively comprehensive disposing the poor phosphorus sludge.It will improve the phosphorus recovery rate, obtain economic benefits and reduce the pollution to the environment.