Method for recycling silver from waste IC chips using soluble starch
A method for recycling silver from a waste IC chip include: heating to disassemble an IC chip, and crushing the IC chip into powders; adding the powders to a nitric acid solution, heating, centrifuging and collecting a first filtrate; adding soluble starch to the first filtrate, where a mass concentration ratio of the soluble starch to Fe in the first filtrate is 5.20-7.30; heating a resulting mixture to 130-175° C. for a first hydrothermal reaction, separating a precipitate from the first hydrothermal reaction and collecting a second filtrate; heating the second filtrate to 160-230° C. for a second hydrothermal reaction, separating a solid from the second hydrothermal reaction and collecting a third filtrate; drying, grinding, and sieving the solid to obtain silver powders; and adding alkali to the third filtrate to form a precipitate of Cu, and separating the precipitate to yield copper hydroxide.
1 . A method, comprising:
1) heating to disassemble an IC chip, and crushing the IC chip into powders;
2) adding the powders to a nitric acid solution to yield a first mixture, heating and centrifuging the first mixture, and collecting a first filtrate comprising iron (Fe);
3) adding soluble starch to the first filtrate obtained in 2) to yield a second mixture, wherein a mass concentration ratio of the soluble starch to Fe in the first filtrate is 5.20-7.30; heating the second mixture to 130-175° C. for a first hydrothermal reaction, separating a first precipitate from the first hydrothermal reaction and collecting a second filtrate;
4) heating the second filtrate to 160-230° C. for a second hydrothermal reaction, separating a second precipitate from the second hydrothermal reaction and collecting a third filtrate; drying, grinding, and sieving the second precipitate to obtain silver powders; and
5) adding alkali to the third filtrate to form a third precipitate of Cu, and separating the third precipitate to yield cupric hydroxide.
2 . The method of claim 1 , wherein the second hydrothermal reaction in 4) is conducted at a higher temperature than the first hydrothermal reaction in 3), with a temperature difference of at least 20° C.
3 . The method of claim 2 , wherein in 3), the mass concentration ratio of the soluble starch to Fe in the first filtrate is 6.0-7.0.
4 . The method of claim 2 , wherein in 3), the first hydrothermal reaction is performed at 140-160° C.
5 . The method of claim 4 , wherein in 4), the second hydrothermal reaction is performed at 160-190° C.
6 . The method of claim 1 , wherein in 3), the first hydrothermal reaction is performed for 320-400 min.
7 . The method of claim 1 , wherein in 3), before conducting the first hydrothermal reaction, the pH of the first filtrate is adjusted to 0.3±0.02.
8 . The method of claim 1 , wherein in 4), the second hydrothermal reaction is performed for 560-640 min.
9 . The method of claim 1 , wherein in 4), the solid is dried at 60-100° C.
10 . The method of claim 1 , wherein in 2), a heating temperature for the first mixture of the powders and the nitric acid solution is 50-90° C.
11 . The method of claim 1 , wherein in 5), the alkali is added to adjust the pH of the first filtrate to 8.2±0.05.
12 . The method of claim 1 , comprising:
1) comprises: heating an adhesive that connects a heat sink and the IC chip with a heat gun at 200-240° C. for 30 seconds, and detaching the heat sink from the IC chip to obtain a detached IC chip; crushing the detached IC chip into coarse particles of a diameter of 2.5-1 cm using a coarse crusher; and further crushing the coarse particles into the powders of a diameter of 0.3 cm using a fine crusher;
2) comprises: pouring the powders obtained in 1) into a glass beaker; adding 3 mol/L nitric acid solution to the powders in a solid-liquid ratio of 1:3 to yield the first mixture; heating and stirring the first mixture in the glass beaker at 50-90° C. with a stirring rate of 300 r/min for 1-2 h; centrifuging the first mixture and passing the first mixture through a filter to yield the first filtrate, so that a filter residue is separated from the first filtrate; the first filtrate further comprises silver and other metals, and the filter residue comprises alloy;
3) comprises: measuring the pH of the first filtrate obtained in 2); adding nitric acid to adjust the pH of the first filtrate to 0.3=0.02 thus yielding a mixed solution; measuring a content of Fe in the mixed solution; pouring the mixed solution into a first reaction kettle and adding the soluble starch to the mixed solution to yield the second mixture, wherein the mass concentration ratio of the soluble starch to Fe in the solution is 5.20-7.30; stirring the second mixture; covering the first reaction kettle and heating the first reaction kettle to 130-175° C. for 300 min to carry out the first hydrothermal reaction, to yield the first precipitate at a bottom of the first reaction kettle; centrifuging a first resulting product in the first reaction kettle, so that the first precipitate is separated from the second filtrate; collecting the second filtrate; and drying the first precipitate at 75° C. for 20 h, wherein the first precipitate is a byproduct of hematite;
4) comprises: transferring the second filtrate obtained in 3) into a second reaction kettle; sealing the second reaction kettle at 160-230° C. for 600 min for the second hydrothermal reaction; after the second hydrothermal reaction, cooling a second resulting product in the second reaction kettle to room temperature and centrifuging the second resulting product to yield the second precipitate and the third filtrate; collecting and drying the second precipitate at 60-100° C., then grinding and sieving the dried second precipitate to obtain silver powders; and
5) comprises: adding 7 mol/L NaOH to the third filtrate to adjust the pH of the third filtrate to 8.2±0.05; resting a third mixture of the third filtrate and NaOH at 30° C. for 5 h; centrifuging the third mixture for solid-liquid phase separation to yield the third precipitate; collecting the third precipitate; and drying the third precipitate at 80° C.