Method for preparing iron silicon sulfur multi-element composite biochar soil heavy metal conditioner

A method for preparing an iron silicon sulfur multi-element composite biochar soil heavy metal conditioner, wherein:

• this method comprises the following steps:
• (1) after mixing biomass with a certain amount of silicate or silicic acid, increasing the temperature to 350° C.-550° C. by 10° C.-25° C. per minute with air isolated and maintaining this temperature for 5-10 h, and then cooling to room temperature with air kept isolated to obtain silicate-containing biochar;
• (2) dissolving an iron-containing compound in water to obtain an iron-containing solution with iron content by mass of 5% to saturation, spraying the iron-containing solution onto a certain mass of kaolinite while stirring the solution, continuing stirring for 30-60 min after completely spraying the solution, and drying to obtain adsorptive iron-containing kaolinite;
• (3) dissolving a sulfur-containing compound in water to obtain a sulfur-containing solution with sulfur content by mass of 5% to saturation, spraying the sulfur-containing solution onto a certain mass of bentonite while stirring the solution, continuing stirring for 30-60 min after completely spraying the solution, and drying to obtain the adsorptive sulfur-containing bentonite;
• (4) fully mixing the materials prepared in the above steps (1), (2) and (3) according to parts by mass of 20:1:1-20:5:5, pulverizing them to pass through a 60-mesh sieve and above to obtain the soil conditioner precursor;
• and
• (5) well mixing the soil conditioner precursor prepared in the step (4), diatomite and starch according to parts by mass of 100:1:2-100:5:10, spraying water for pelleting, and drying to obtain the iron silicon sulfur multi-element composite biochar soil heavy metal conditioner.