Preparation of soil nutrient amendment using white mud produced in ammonia-soda process and its environmental assessment

A novel method to prepare soil nutrient amendment by calcining a mixture of white mud and potassium feldspar and its environmental assessment were investigated. Under the optimal conditions of a blending mass ratio of 70:30 for white mud to potassium feldspar, a calcination temperature of 1 000 °C, a calcination time of 1.5 h and spherulitic diameter of 2.0 cm, the calcined product, as a soil nutrient amendment, could be prepared with the following nutrient composition (mass fraction): K₂O 4.16%, CaO 23.43%, MgO 5.04%, SiO₂ 22.92%, SO₄²⁻ 3.71%, and Cl⁻ 3.87% in 0.1 mol/L citric acid solution. The concentrations of heavy metals in the calcined product and the emission concentrations of harmful gases from a mixture of white mud and potassium feldspar during calcination process could qualify the National Standards without causing secondary environmental pollution.