Phosphorus forms and potential release characteristics of phosphogypsum in Tuojiang River basin

The phosphorus form and content, release kinetics characteristics of phosphorus and the influence of environmental factors on phosphorus release were investigated from phosphogypsum samples collected in Tuojiang River basin. The results showed that the TP content of phosphogypsum was 3.70 mg/g, and the release of phosphorus was mainly carried out by Ex-P, Org-P and Fe-P. Among them, Ex-P and Fe-P accounted for a large proportion. When the ratio of water to phosphogypsum was 500 ∶1, the phosphorus release reached the maximum value, and the phosphorus release mainly occurred in the first 8 hours. The maximum release rate of phosphorus from phosphogypsum was 3.52 mg/(g ·h). The first order kinetic equation can fit the phosphorus release kinetic process well with the maximum release Q_max of 2.30 mg/g under the experimental condition. The pH had significant effect on phosphorus release from phosphogypsum, and either acidic or alkaline water environment was conducive to release of phosphate. Higher salinity and temperature were favorable to the release of phosphorus, and total phosphorus release increased the most as temperature increasing from 10 to 25 ℃ with the maximum at 25 ℃.