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1 Production of ruber sodium using chromium sludge
The trivalent chromium can be oxidized to Na2Cr2O7 by air in Na2CrO4, which is a basic medium with high temperature. At the same time, the iron, zinc, etc. contained in the sludge is converted into the corresponding soluble salts NaFeO2, Na2ZnO2. Most of the alkali melts are leached with water. The iron is decomposed into Fe(OH)3 precipitates and removed. The filtrate was acidified to pH<4, and Na2CrO4 was converted to Na2Cr2O7. The solubility of Na2SO4 and Na2Cr2O7 were different and crystallized separately. The conditions for the production of sodium erythromycin using a high-temperature alkaline chromia sludge are n(Na2CO3):n(Cr2O3)=3.0:1.0, a temperature of 780C, a time of 2.5 hours, and a chromium conversion rate of 85% or more.
2 Production of chrome yellow
Soda ash is used as a precipitant to remove the metal ions in the electroplating waste liquid, and then the purified electroplating waste liquid is used instead of a portion of the erythrosine sodium to produce lead chrome yellow. After adding the saturated solution of Na2CO3 to the plating solution, the pH was adjusted to 8.5 to 9.5. The solution was filtered and the filtrate was used as a backup. Under alkaline conditions, the Cr3+ in the residue is oxidized to Cr6+ with H2O2. After filtration, the filtrate is mixed with the above filtrate. The filtrate and lead nitrate solution and additives, at 50 ~ 60 °C reaction 1h, and then filtered, washed with water, washed away chloride, sulfate and other soluble impurities, and then dried and crushed to obtain the finished lead chrome yellow. The use of electroplating waste liquid to produce lead chrome yellow not only solves the pollution problem, but also makes chromium in electroplating waste liquid recycled. It is estimated that 200 tons of electroplating waste liquid will be treated annually, with an average annual recovery of 18 tons of sodium erythromycin, which can achieve an annual income of more than 40,000 yuan. The benefits are considerable.
3 Production of liquid chrome tanning agents and leather tanning agents
The chromium-containing waste liquid is first removed with sodium hydroxide to remove metal ion impurities, and the pH is controlled to be 5.5-6.0. Then, the filtrate is used for filtration, and the sludge is treated with a harmless ferrite. Then, the reducing agent is added to the filtrate glucose, Na2Cr2O7 reduced to Cr (OH) SO4, further polymerization at 100 °C, when the basicity is 40%, the molecular formula 4Cr (OH) 3.3Cr2 (SO4) 3 It is a chrome tanning agent. A leather factory in Wuji County, Hebei Province, utilizes electroplated chromium-containing wastewater to produce liquid chrome tanning agent. According to the daily production of 5t liquid chrome tanning agent, the daily profit can be more than 6,000 yuan. It can be seen that the economic benefits of the production of chromium tanning agent using chromium-containing waste liquor are very significant.
In addition, chromium-containing sludge can be mixed with carbon powder and calcined at a high temperature to obtain metallic chromium. Since chromium-containing sludge is the main species of electroplating plant sludge, sludge recovery is different according to the plating treatment method. Use is also different. Electrolysis sludge:
(1) Raw materials for medium temperature shift catalysts;
(2) Raw materials for iron-chromium red pigments.
Chemical sludge:
(1) Recovery of chromium hydroxide;
(2) Recovery of chromium oxide polishing paste. Ferrite sludge is used as raw material for magnetic materials and so on.
Comprehensive Utilization of Electroplating Chromium Waste Liquid and Sludge
Because the electroplating chromium-containing aged waste liquid has a high content of harmful substances and complex components, various waste liquids should be treated separately and categorized before comprehensive utilization. For the galvanized passivation solution, copper passivation solution and aluminum electrolysis polishing solution containing phosphoric acid, pH is adjusted with an acid base; for anion exchange resin, it is only necessary to change it to Na2CrO4.