1. The treatment of chromium-containing waste liquid mainly comes from chromic acid waste liquid. Treatment of chromium-containing waste liquid produced in the analysis experiment of potassium dichromate titration waste liquid: firstly, under acidic conditions, reducing agents such as human iron filings, FeS04 or sulfide and sulfite are added to the chromium-containing waste liquid to reduce highly toxic Cr0' to less toxic Cr ",and then waste alkali liquor or sodium hydroxide, calcium hydroxide and quicklime are added to adjust the pH value of the solution to about 7. CrI 1 is converted into low toxic Cr(OH) precipitate, and the separated clear liquid can be directly discharged. After dehydration and drying, the sediment can be comprehensively utilized or roasted. The treated chromium slag can be mixed with cement and buried underground after solidification.
2. Treatment of waste liquid containing lead and bismuth
The continuous determination of bismuth and lead in mixed solution by complexometric titration is an important experiment for quantitative analysis, and it is also the main source of lead and bismuth waste liquid. If the waste liquid produced in this experiment is directly discharged, it will do great harm to the environment and human body, and it will also waste valuable resources. Therefore, the following methods can be used to treat the waste liquid first and then recycle it directly.
(i) Take 2500mL of concentrated waste liquid after continuous determination of lead and bismuth in a 3000mL beaker at a time, heat it to near boiling in an electric furnace, take it out, and add 2mol/L Na while stirring until the PH value of the waste liquid is 12.
5- 13.0, fully stirring and standing for precipitation (stirring twice). Due to the existence of strong electrolytes such as hexamethylenetetramine salt and Na in the solution, sulfide will precipitate rapidly, and its supernatant will be purple, which is the color of xylenol orange indicator under alkaline conditions.
(2) After decanting the supernatant of the inner core layer, rinse the sulfide precipitate produced by each dumping with tap water of about 1.500ml for three times, and then rinse it twice with a small amount of deionized water, and finally make the volume of sulfide precipitate and water about1.500ml.. After thoroughly washing the precipitate with water, add 65,438+0.4 ml of concentrated HNO and heat until the black sulfide is completely dissolved. Remove nitrogen oxides, cool and filter, and finally dilute the filtrate to 830mL. It is worth noting that the acidity of the regenerated mixed solution is just within the pH value range of 0.7- 1 ... It is needed for titration of Bi' with EDTA, so it does not need to be neutralized with sodium hydroxide, and can be directly reused in the next experiment. Moreover, the lead and secret recovery rate of this method are above 99%, which is a good way to protect the environment and save resources.
3. Disposal of waste liquid containing mercury
This method mainly comes from the reaction process of pretreatment agent SnC 1-HgC 1: for iron content determination in iron ore, and generally adopts:
(1) chemical coagulation and precipitation method: firstly, adjust the pH value of the mercury-containing waste solution to 8- 10 with NaoH, add excessive iron sulfide or sodium sulfide to make it generate mercury sulfide precipitation, then add a certain amount of ferrous sulfate as flocculant to adsorb mercury sulfide particles suspended in water and precipitate them together, and then stand, separate or centrifugally filter, and the clear liquid can be directly discharged into the sewer.
(2) Amalgam extraction method: adding human zinc chips or aluminium scrap into the mercury-containing waste liquid, so that the mercury in the waste liquid can be easily replaced by zinc or aluminum, and mercury can generate zinc amalgam or aluminum amalgam, thereby purifying the waste water. Impurities that form amalgam with mercury can also be removed by electrolysis, and then high-purity mercury can be obtained by vacuum distillation.
4. Treatment of arsenic-containing waste liquid
Calcium arsenate and calcium arsenite can be precipitated by adding human quicklime into arsenic-containing waste liquid and adjusting the pH value to about 8, and they can be precipitated together when Fe exists. After the sediment is separated, the filtrate can be directly discharged into the sewer, and the residue can be treated as waste residue.
5. Treatment of cyanide-containing waste liquid
(1) If the content of CN- is low, KMn0 oxidation method should be adopted, that is, NaOH is added to the waste liquid to adjust the pH value to above 10, and then 3%KMn0 is added to oxidize and decompose CN;
(2) If the content of CN is high, alkaline chlorination can be used, that is, NaOH is added to the waste liquid to adjust the pH value to above 10, and sodium hypochlorite is added to oxidize and decompose CN.