Release characters of non-exchangeable potassium from potassium bearing minerals in NaBPh₄ solutions

The total K content, total non-exchangeable potassium (NEK) content and NEK release rate of 5 K-bearing minerals (phlogopite, biotite, vermiculite, muscovite and feldspar) were compared in current study. The results indicated that the total K, total NEK and NEK release rates of the minerals differed greatly, and the three parameters were not significant correlated. The total NEK content followed the order of phlogopite (5.19%) biotite (3.08%) vermiculite (2.01%) muscovite (1.18%) feldspar (0.24%), accounting for 58.4%, 99.7%, 62.5%, 14.2% and 4.98% of the total K, respectively. The release characteristics of the NEK from 5 minerals was investigated during a 3d extraction with NaBPh4 method with low K-extracting power, the amount of NEK released from minerals followed the sequence of biotite vermiculite phlogopite muscovite feldspar. The averaged NEK release rates from 5 minerals followed the same order and were 5.99, 2.34, 0.52, 0.22 and 0.17 mg/(kgmin), respectively. How to evaluate the K availability in minerals according to the amount and the release rate of NEK was still a question need to be addressed in future.