Heavy Metal Recovery From Waste CRT Funnel Glass By The Combined Process Of Rapid Phase-separation And Mechanical Activation Leaching Process

Waste cathode ray tube（CRT）funnel glass contains a large number of heavy metals.And the safe disposal and recycling technology of CRT funnel glass is one of the urgent problems to be solved in the pollution control of electronic waste in China.In this paper,waste CRT funnel glass was taken as the research object.The heavy metals such as lead,barium and strontium contained in CRT funnel glass were recovered and high silica glass powder with high economic value was obtained by the rapid phase separation method combined with mechanical activation leaching process.By studying the migration and transformation of heavy metals in funnel glass during the rapid phase separation process and mechanical activation leaching process,the main factors and action mechanism affecting the removal rate of heavy metals were revealed,the green reuse technology of extractant was discussed,and the whole set of process parameters were optimized.The main conclusions are as follows:（1）In the process of rapid phase separation,the existing forms of heavy metals such as lead,barium and strontium in the glass phase of CRT funnel glass exhibited no obvious change,but these heavy metals could quickly migrate and enrich in the B₂O₃-rich phase.With the increase of melting temperature,holding time and the amount of B₂O₃addition,the distribution rate of heavy metals in the B₂O₃-rich phase increases gradually.When the the amount of B₂O₃addition was 20%and the funnel glass was melted at 1000℃for 30 min,the distribution rates of lead,barium and strontium in the B₂O₃-rich phase were 99.77%,99.93%and 99.76%respectively.（2）The B₂O₃-rich phase in the rapid phase separation product of CRT could be rapidly dissolved in water under the action of mechanical activation.Various heavy metals or other metals contained in the B₂O₃-rich phase were released into water and quickly captured by EDTA to form water-soluble metal-EDTA.Therefore,the mechanical activation leaching method can efficiently and environmentally recover the heavy metals Pb,Ba and Sr and other metals K,Ca,Mg and Al in the phase separation products of CRT funnel glass,so as to overcome the problem of environmental pollution caused by the traditional strong acid leaching method after phase separation.（3）EDTA has the best chelating effect on heavy metals and EDTA was selected as the extractant among EDTA,NTA and Na₂EDTA.The extraction rate of heavy metals increased with the increase of EDTA addition,ball milling speed and ball milling time,but it shows a trend of first increasing and then decreasing with the increase of water/solid ratio.When the mass percentage of EDTA addition and treated phase separation product,the rotational speed,the water/solid ratio and the ball-milling time were fixed at 80%,500rpm,0.8,and 30 min,respectively,the respective extraction rates of Pb,Ba,and Sr by mechanochemical extraction were 98.79%,95.79%and 94.91%,while the extraction rates of K,Ca,Mg and Al were 94.92%,95.17%,84.96%and65.71%,respectively.The purity of Si O₂ in the obtained solid residue was 92.71%.（4）Heavy metals can be efficiently recovered from the leaching solution through sulfate precipitation.Pb（Ba or Sr）-EDTA（lq）reacted with Fe₂（SO₄）₃ to form sulfate precipitation（Pb SO₄,Ba SO₄,or Sr SO₄）and Fe-EDTA（lq）.Then,the Fe-EDTA aqueous solution was changed into the Na₂EDTA basic aqueous solution by the addition of Na OH（p H=13）,while Fe ions can be recovered as Fe（OH）₃（s）.Finally,Na₂EDTA（lq）changed into EDTA（s）again by adding a suitable amount of HCl when the p H value of the Na₂EDTA basic aqueous solution was<3.The recovered EDTA（s）could be reused in the mechanical activation leaching process.