The most common chemical laboratory is acid-base waste liquid. Generally, the waste liquid from glassware cleaning can be directly discharged because it has been washed with a lot of water and its concentration is extremely small. High-concentration acid-base waste liquid should be stored separately at ordinary times, mixed regularly and treated in the middle, so as to treat waste with waste and make its PH value between 6. Number five and number eight. 5. Meet the emission standards.
2. Mercury and waste liquid containing mercury
If the thermometer is broken or the polarographic analysis is wrong, the body mercury must be removed in time, and the dropper and cotton should be used.
Or the thin copper sheet and thick copper wire immersed in the acidic solution of mercury nitrate are collected in a beaker and covered with water. Small mercury beads scattered on the ground that are difficult to collect should be sprinkled with sulfur powder as soon as possible to convert them into less toxic mercury sulfide and then cleaned up; Or spray 20% ferric chloride aqueous solution, dry and then clean. Mercury-containing solution includes organic mercury and inorganic mercury. Organic mercury waste liquid is decomposed into inorganic mercury by adding appropriate oxidant, and the PH value of inorganic mercury waste liquid is adjusted to 8- 10, because the solubility product of mercury sulfide is very small, which is 4× 10- 53. Therefore, H2 S, Na2 S, NaHS and (NH4 )S are commonly used as reagents to precipitate mercury, and Hg+ and Hg2+ ions are transformed into insoluble Hg2 S and HgS precipitates. Because mercury is highly toxic, the filtrate is treated with activated carbon and then filtered and discharged.
3. Treatment of chromium-containing waste liquid
The main sources of chromium-containing wastewater are oxidation wastewater, electroplating wastewater, chromium pickling solution and preparation of organic compounds. This kind of waste liquid generally contains two valence states of chromium (Ⅲ) and chromium (ⅵ), which is very toxic. Reducing agents such as ferrous sulfate, sodium bisulfite, sulfur dioxide, hydrazine hydrate or iron filings can be added to the chromium-containing waste liquid to reduce Cr (ⅵ) to Cr (Ⅲ) under acidic conditions, and then alkali such as NaOH, Ca(OH) 2 and Na2CO3 can be added. PH value can be adjusted by adding Cr (Ⅲ) to form low toxic Cr (OH) 3 precipitate, and the clear liquid is discharged.
4. Treatment of cyanide-containing waste liquid
Cyanide-containing wastewater mainly comes from electroplating experiments and metallurgical experiments. The PH of low-concentration cyanide wastewater can be adjusted to above 10 by adding NaOH, and then HClO (about 3%) is added, and the CN- is oxidized and decomposed, and the toxic CN- is converted into nontoxic CO2 and N2.
Sodium cyanide+sodium hydroxide+perchloric acid = sodium cyanide+sodium chloride +H2O
2 nacno+2 hclo = 2 CO2 ↑+ N2 ↑+ H2 ↑+ 2 NaCl
Waste liquid containing cyanide shall not be mixed with acid, so as to avoid producing highly toxic HCN gas and causing poisoning.
5. Treatment of waste liquid containing silver
The waste liquid containing silver in chemical laboratory mainly comes from silver content analysis, silver mirror reaction and electroplating, and mainly exists in the form of AgNO3 and Ag(NH3)2+. There are many ways to recover silver, and we have screened out the method with simple operation and high purity through experiments. Adjust the PH value of the waste liquid with HCl, add NaCl for precipitation, and wash the obtained white solid with nitric acid, then filter and recover.
6. Treatment of waste liquid containing phosphorus
Phosphorus-containing waste liquid mainly comes from electroplating, surfactant experiment and cleaning waste liquid. Serious pollution, long residual time, difficult degradation, great harm to human health, difficult to deal with. Rectorite [5] is a kind of clay mineral with regular interlayer formed by mica-like layer and montmorillonite-like layer. When it swells and disintegrates in water, the particle size in water is generally1-2 μ m. Rectorite has a large hydrophilic surface and shows good hydrophilicity, dispersibility and expansibility in aqueous solution. Phosphorus-containing waste liquid is adsorbed by rectorite and reaches the discharge standard. At the same time, rectorite can be washed and recycled.
7. Treatment of aromatic nitration wastewater
Aromatic nitration wastewater mainly comes from aryl nitration experiment, and mixed acid nitration method is generally used. The pollutants produced in the process mainly include 2- nitrophenol, 4- nitrophenol and 4. 6- dinitrophenol, 2. 6- dinitrotoluene, 2.6- dinitrotoluene and nitrobenzene are highly toxic and difficult to treat. The wastewater has a deep sauce color and an unpleasant smell. The concentration of phenol is greater than 0. COD reaches 1 100mg/L, which belongs to high concentration organic wastewater. Laboratory treatment includes adsorption of activated carbon and sulfonated coal, complex extraction and chemical oxidation. In particular, adsorption method has the advantages of short process, simple operation and high treatment efficiency, and is suitable for the treatment of nitro wastewater.
8. Treatment of organic waste liquid containing amine
Organic waste liquid containing amine mainly comes from experiments such as dye intermediates and drug intermediates. The extraction of amine-containing organic waste liquid [6] by complex extraction method has quite high COD removal rate, and all indicators of waste water meet the requirements of laboratory discharge, and the process is simple, with less equipment investment, low operating cost and convenient operation.
9. Treatment of high concentration organic waste liquid
High-concentration organic wastewater mainly comes from washing, crushing and extracting effective components from natural animals and plants, and some of it comes from ineffective organic reagents, which has the characteristics of high organic concentration, high SS, low pH value and great water quality change. The biochemical treatment process [7] based on hydrolytic acidification and contact oxidation can not only effectively remove the organic matter and suspended matter in water, but also run reliably, with low treatment cost and good treatment effect, and the effluent quality meets the requirements.