Fertilizer values from galvanizer waste

A process for winning valuable agricultural micronutrient values from hazardous materials normally derived from galvanizer waste by-products, said hazardous materials selected from the group consisting of spent sulfuric acid, iron sulfate, zinc sulfate, and mixtures thereof, and said micronutrient values comprising elemental iron and zinc, which process comprises the steps of:

• (a) securing as feedstock to said process, aqueous media comprising iron sulfate and selected from the group consisting of spent sulfuric acid containing from about 1 to about 3 percent, by weight, of Fe, and from about 2 to about 6 percent, by weight, Zn, an aqueous solution or slurry prepared from iron sulfate containing from about 1 to about 10 percent, by weight, Fe, an aqueous solution or slurry prepared from iron sulfate and zinc sulfate, said aqueous solution or slurry prepared from said iron sulfate and/or zinc sulfate containing from about 1 to about 10 percent, by weight, of Fe, and/or from about 1 to about 10 percent, by weight, Zn said amounts of Fe and Zn being essentially in dependent and inversely proportional relationship to one another, and mixtures thereof;
• (b) introducing at least a portion of said feedstock secured in step (a) supra into first reactor means;
• (c) introducing into said first reactor means ammoniating media, said ammoniating media selected from the group consisting of anhydrous ammonia, aqueous ammonia, and mixtures thereof, for a time and in predetermined quantity sufficient to raise the pH of the materials therein up to the range of from about 9 to about 11 and to result in the partial ammoniation thereof;
• (d) maintaining the temperature of the materials in said first reactor means in the range of from about 20.degree. C. to about 100.degree. C. during said partial ammoniation in step (c) supra;
• (e) removing at least a portion of the resulting partially ammoniated material from said first reactor means and introducing same into second reactor means;
• (f) introducing into said second reactor means oxidizing media, said oxidizing media selected from the group consisting of air, oxygen, and mixtures thereof and contacting said portion of said resulting partially ammoniated material introduced therein with said oxidizing media for a time and in quantities sufficient only to result in the conversion of from about 67 percent to about 75 percent of the total Fe in said partially ammoniated material to Fe.sup.+++ ;
• (g) subsequently discontinuing the contacting of said material in said second reactor means with substantial additional quantities of said oxidizing media;
• (h) reacting autogenously, the material resulting from the contact in said second reactor means of said partially ammoniated material with said oxidizing media from step (f) supra, for a period of time sufficient to allow for the substantially complete reaction of the unoxidized ferrous hydroxide with the ferric oxide to thereby result in the formation of magnetite;
• (i) introducing at least a portion of the substantially reacted material from step (h) supra into gravity type liquid/solids containing separation means;
• (j) subjecting the material juxtaposed at least the lower region of said separation means to the influence of substantial magnetic flux to thereby enhance the gravitational separation of the magnetite therein;
• (k) removing from said separation means the liquid portion, said liquid portion containing greater than about 90 percent, by weight, of the zinc and less than about 1 percent, by weight, of the iron originally contained in said feedstock;
• and
• (1) removing from said separation means the solids containing portion, said solids containing portion containing greater than about 99 percent, by weight, of the iron and less than about 10 percent, by weight, of the zinc originally contained in said feedstock.