The invention provides a method for preparing nano-hydroxyapatite. The method comprises the following steps of dissolving
calcium-containing
slag into acid, removing impurities which are not dissolved in the acid by means of filtering, adjusting a pH value to an alkaline level, removing impurities which are not dissolved in alkali by means of filtering again, and obtaining a
calcium salt solution; mixing the
calcium salt solution with a
phosphate solution, adjusting the pH value of the
mixed solution to the alkaline level, and reacting to obtain the nano-hydroxyapatite. Compared with the prior art, the nano-hydroxyapatite prepared according to the method provided by the invention has the advantages that factory
slag is taken as a
raw material, the factory
slag is cheap and is easily and widely obtained, the effect of turning waste into treasure is achieved, the nano-hydroxyapatite is friendly and harmless to the environment, and the technology is simple; the
dispersity is excellent, the particle diameters are uniform, and the adsorption of heavy
metal ions in
wastewater is beneficially performed; the prepared nano-hydroxyapatite has a proper
mechanical property and an excellent
processing property, and the environment can be prevented from secondary
pollution during the process of treating heavy
metal in the
wastewater, therefore the nano-hydroxyapatite is widely used in the field of
water treatment.