According to the industrial-grade monoammonium
phosphate sludge treatment method and the liquid
fertilizer provided by the invention, the
phosphoric acid solution is neutralized by
ammonia water, and the pH value of the
system is limited, so that impurities in liquid-phase monoammonium
phosphate are reduced as much as possible, and an iron element is left in
sludge; a
citric acid solution is added into the
sludge to carry out
chelation reaction on
metal ions in the sludge to control the pH value to be 4.0-7.0, then a
raw material phosphoric acid solution for preparing monoammonium
phosphate is added, the pH value of a
system is adjusted to be not higher than 4.0, the water
solubility and stability of iron elements in the sludge are remarkably improved, non-water-soluble
ferric phosphate salt in the sludge is converted into a water-soluble chelate, and the water-soluble chelate is converted into the sludge. The obtained liquid
fertilizer is more easily absorbed by crops, high-value utilization of sludge is achieved, the obtained liquid
fertilizer can form a soil environment where beneficial microorganisms move, a good
soil aggregate structure is formed, and the soil improvement effect is obvious.