The treatment of harmful substances in waste liquid is mainly to recover or decompose and transform harmful substances into other non-toxic or low-toxic compounds through physical processes and chemical reactions. Here are some ways to deal with hazardous waste. 1. The processing of arsenic-containing waste Arsenic trioxide is a highly toxic substance with a lethal dose of 0.1 g. The concentration in the solution must not exceed 5 × 10 -5 %. Compounds may form ferric hydroxide precipitate arsenic with iron under basic conditions using sulfuric acid processing coprecipitation and adsorption, to remove arsenic in the waste water. Note that the molar ratio of Fe 3+ to As 3+ is about 10:1, and the pH value is about 9, which is best. After stirring well, it is allowed to stand overnight, the precipitate is separated, and the waste liquid is discharged. Fe 3+ + 3OH -  = Fe(0H) 3 ↓ As 3+ + 3OH -  = As(0H) 3 ↓ 2. Treatment of chromium- containing waste liquid Cr(VI) is highly toxic and should not exceed 5 × 10 -5 % in solution. In the acidic (pH 2 to 3) chromium-containing waste liquid, about 10% of ferrous sulfate solution is added, and Fe 2+ can reduce Cr(VI) to Cr 3+ . Then adjust the pH of the solution with slaked lime or lye to 6-8 (to prevent Cr(OH) 3 from being converted to Cr(OH)4-) when the pH is greater than 10, heat to about 80 °C, let stand overnight, separate the precipitate, discharge waste liquid. Fe 2+ + 2OH -  = Fe(0H) 2 ↓ Fe 3+ + 3OH -  = Fe(OH) 3 ↓ Cr 3+ + 3OH -  = Cr(OH) 3 ↓ 3. Treatment of cyanide-containing waste liquid Cyanide is highly toxic and should not exceed 1.0 × 10 -4 % in solution. We use the strong coordination of CN - ion and treat the cyanide-containing waste liquid by the Prussian blue method. First, add the alkali solution to the waste liquid to adjust the pH to 7.5-10.5, then add about 10% of the ferrous sulfate solution, stir well, and then settle the precipitate after standing, and discharge the waste liquid. Fe 2+ + 6CN - = [Fe(CN) 6 ] 4-  2Fe 2+ + [Fe(CN) 6 ] 4-  = Fe 2 [Fe(CN) 6 ]↓ 4. The process of mercury-containing waste The mercury-containing waste liquid is extremely toxic, and its minimum concentration should not exceed 5.0×10 -7 %. If the waste liquid is treated by microorganisms, it will become more toxic organic mercury. Hg 2+ can be converted to HgS by Na 2 S, and then co-precipitated with FeS to be separated and removed. Hg 2+ + S 2-  = HgS ↓ Fe 2+ + S 2-  = FeS ↓ The processing of lead-containing waste The concentration of lead-containing waste liquid must not exceed 1.0 × 10 -4 %. It can be treated by hydroxide coprecipitation. With lye is adjusted to pH 11, the Pb 2+  into insoluble Pb (OH) 2 precipitate, and then adding an aluminum salt coagulant Al 2 (SO 4) 3 3 to make the generated precipitate Al (OH), this When the pH is 7-8, Al(OH) 3 and Pb(OH) 2 coprecipitation are produced. After standing and clarifying, the precipitate was separated and the waste liquid was discharged. Pb 2+ +2OH - = Pb(OH) 2 ↓ Al 3+ + 3OH - = Al(OH) 3 ↓ 6. Cadmium 90% of the cadmium used in electroplating, pigments, alloys and batteries, cadmium practical wastewater treatment contains environmental monitoring station laboratory precipitation, adsorption. Using the precipitation method, the precipitant has hydroxide, sulfide, polyferric sulfate, using hydroxide, the pH is controlled above 10, which can achieve satisfactory results; the use of sulfide PH is controlled above 9; using polymeric ferric sulfate pH control 8.5 to 9.5 range. The adsorption method can use activated carbon, weathered coal , and sulfonated coal as adsorbents. 7. Phenol With the rapid development of petrochemical, plastics, synthetic fibers, coking and other industries, a variety of phenol-containing waste water is correspondingly increased, high toxicity of phenol, using activated carbon as an adsorbent is a viable approach. For other toxic and hazardous organic wastewater, laboratory technicians can also use this method. Hydraulic Gear Pump,Gear Pump,High Pressure Gear Pump,Stainless Steel Gear Pump GRH , https://www.grhcn.net