Using chemical experiments and plant uptake to prove the feasibility and stability of coal gasification fine slag as silicon fertilizer.

Coal gasification fine slag (CGFS) is a kind of industrial waste that is generated from entrained-flow coal gasification with a high content of 0.5 M hydrochloric acid (HCl)-extractable silicon (Si). Si fertilizer has been widely used in agriculture to enhance the mechanical properties and yield of crops. An evaluation was actualized by analyzing HCl-extractable Si fractions and X-Ray diffraction (XRD) of different treatments (acid, alkali, salt, grind, calcination, temperature, and time) for CGFS samples and other Si source materials. The results showed that CGFS had stable HCl-extractable Si concentrations of 60 ± 2 g/kg except in the calcination treatment, which decreased the content of extractable Si by 28.2%. Furthermore, under the same processing conditions, CGFS showed a higher content of extractable Si than other Si source samples. Moreover, a rice growth experiment was carried out for 120 days in a different mass incorporation of CGFS in the greenhouse. The strength index and total Si content of the stem proved that using CGFS at 5 wt.% markedly promoted the growth of rice. The study indicated that an appropriate application of CGFS as a Si resource to an agricultural field could be considered as a viable option for safe disposal of this industrial waste.