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There are more pollutants in the production process of circuit boards, and the wastewater mainly contains copper, chromium, nickel, zinc, acids and wastewater alkalis, etc. If not treated effectively, it will cause serious pollution to the natural environment of the water body. Alkalis, heavy metal contamination of water mats are destroyed, damage the water quality, inhibit or block the activities of microorganisms, reduce the self-cleaning ability of water, and at the same time will cause damage to plants, heavy metal ions are the most dangerous to health, heavy metal ions in the water will not be degraded by microorganisms, they will be absorbed in the living organisms, accumulated and enriched, harmful to humans, fish and plankton, and in serious cases, will lead to the death of plants or livestock deaths. It should be treated maliciously and managed strictly according to the environmental protection requirements to meet the emission standards.
Circuit Board Wastewater
The quality of circuit board wastewater is a complicated process in the circuit board printing industry, and must be handled in accordance with the classification of water quality.
1.General circuit board printing wastewater contains the following components:
Heavy metals: Cu, Ni, Pb, Sn, Mn, Ag, Au, Pd and so on.
Organic matter: all kinds of electroplating or chemical plating additives, network compounds, cleaning agents, inks, stabilizers, organic solvents, etc.
Inorganic substances: acid, alkali, NH3-N (NH3 or ammonium salt), P (various phosphate salts), F, etc.
2.Wastewater diversion should be divided into more than three types: Cu, Cu complexes and organic substances. Ni and CN can be decided according to the actual processing needs of the diverter.
3.Deletion film (deletion Film, film) wastewater is mainly composed of ink anticorrosive,photographic liquid.COD concentration is very high, is the source of COD PCB industrial wastewater. Because of the main special chemical properties, should be treated separately with.
4.The heavy metals Cu and Ni should be separated from the ions in the wastewater and treated separately.
5.Waste liquid should be collected separately.
Circuit board wastewater treatment
1.Pre-treatment technology of ink waste liquid
Ink waste liquid mainly refers to the waste liquid in the developing and stripping process, which contains a large amount of photographic film, solder-resistant film residue, etc. The waste liquid is alkaline, with a pH value of 11 to 13; the COD content is very high, ranging from 8000-10000mg.Waste liquid is alkaline,PH value is generally between 11~13; COD content is very high, the range is generally 8000-10000mg / L.
The main component of the ink waste liquid is organic acid salts generated by the resin containing hydroxyl groups under alkaline conditions, and these resin containing hydroxyl groups are not easily soluble in acidic solutions. Applying this basic nature, in the treatment of developing,stripping waste liquid can be taken to waste treatment method, the use of waste acid discharged from the production plant on the ink waste liquid in the acidification treatment, can be insufficient to add sulfuric acid solution.
2.Networking wastewater treatment technology
Networking wastewater mainly refers to the rinse water discharged from acidic/alkaline etching lines and PTH production lines, the acid and alkali value of this kind of wastewater is generally between 4 and 9, and the wastewater contains not only the network agent (the main network agent has ammonia <50mg/L, formaldehyde, EDTA, etc.), but also a large number of metal ions (e.g., Cu2+<100mg/L), and the network agent and the heavy metal ions, such as copper ions, form a very stable network complex, which can be stabilized by the use of the network agent. The liaison agent and heavy metal ions such as copper ions form a very stable liaison compound, and it is very difficult to treat the wastewater to meet the discharge standard by using the general flocculation and sedimentation method.
Generally the copper ion will precipitate under the alkaline condition, however, in the production process of the circuit board,some crafts must carry on the copper plating under the alkaline condition, so it adds some chemical agents such as EDTA to make it and the copper ion to combine, and the combining ability is stronger than the Cu (OH0)2, and at the same time does not produce the precipitation. This is in this case copper ions can coexist with OH-, so if this kind of wastewater to get rid of copper, we have to first break the network and then remove the copper. Due to the need of treatment technology, the pre-treated backwash water of reuse water system and the filtrate of filtration machine are mixed in the treatment process.
At present some commonly used broken network methods are:direct broken network method, replacement broken network method,chemical precipitation method, heavy metal trap precipitation method, ion exchange method.
3.Containing cyanide wastewater treatment technology
Containing cyanide wastewater mainly comes from electro-nickel gold production line and sinking nickel gold production line, electro-gold or sinking gold process after rinsing water,this kind of wastewater contains high toxicity CN- (<20mg/L), environmental protection requirements for this kind of wastewater should be collected independently, target treatment.
Hydrocyanogen ions can not be removed directly by general flocculation and precipitation method,it must be oxidized to break the structure of its chemical bond, and finally make it degraded to form CO2 and N2 to be removed.
4.Organic wastewater treatment technology
Organic wastewater mainly refers to the wash water after developing and de-filming, as well as the wash water of cleaning nets, making nets, degreasing, etc. This kind of wastewater contains traces of copper (Cu2+<5mg/L), alkaline water (pH=8~10), SS content exceeding the standard and COD content within 500mg/L.The organic wastewater contains a small amount of heavy copper (Cu2+<5mg/L), and its chemical bond structure is broken, and CO2 and N2 are eventually formed and removed.Organic wastewater contains a small amount of heavy metal ions, COD high, SS high,poor biochemistry,does not have the conditions for direct biochemistry,the first coagulation and precipitation method to remove heavy metal ions in wastewater,the vast majority of SS and part of the COD to improve the biochemistry of organic wastewater,and then enter the biochemical system.Biochemical system we choose A/O treatment pipeline, A/O process is anaerobic - aerobic biotechnology in short, the process was created in the early 80s, the process of anaerobic reactor (hydrolysis acidification tank) placed in the front of the system,the purpose is to hydrolyze acidification bacteria will be large molecules of organic decomposition of small molecules of organic matter to further improve the biochemistry of wastewater.The aerobic process is contact oxidation method,its central processing structure is the contact oxidation tank, which is characterized by direct aeration under the filler, the biofilm by the impact of the rising airflow, agitation, accelerate the shedding,renewal,so that it often maintains a better activity, can avoid clogging.
Above we share the composition of the circuit board wastewater, classification and circuit board wastewater process, circuit board wastewater treatment in the circuit board printing industry is very complex, must be classified according to the water quality for treatment.