Assessment On The Environment Risk Of The Recycling Of Nonmetallic Materials From Waste Printed Circuit Boards

Waste printed circuit boards are an important part of electronic waste and have good recycling value. In the case of resource shortage, how to effectively reuse the useful materials in WPCBs has become a hot topic. At present, the recycle of WPCBs mainly focus on the metals fraction while researches on nonmetallic materials (NMs) fraction are rare. The main treatments of NMs are land filling and combustion, which not only increased the environment load but also polluted the environment. Our research group used NMs to replace the conventional filler to produce reproduction plates (RNMP), phenolic model composites (PMC) and wood plastic composites (WPC). However, NMs contain various hazardous substances, so the potential environment risk should not be neglected. This paper is on the research of the potential environment risk in the whole process of NMs recycle.1. Characteristics and potential harm of NMsThe microstructure of NMs with grain diameter less than 0.07mm showed that resins peeled off from glass fiber yarns and on the surface of glass fiber yarns there were some residual resins. The crush degree can affect the leaching degree of hazardous substances. The element detecting result showed besides C, H and O elements, NMs also contains elements of Cu, Pb, Hg and Br. According to RoHS in Europe and"Limit requirement of hazardous substances in electronic information products"in China, though NMs are low risk materials, the environment risk should not be ignored.2. Volatilization of NMs and reproduction materialsNMs with grain diameter less than 0.07mm were reused as filler to produce RNMP, PMC and WPC. The detecting results of volatilization of these three reproduction materials show that the main volatile organic composites (VOCs) from NMs are styrene, lemonene and benzaldehyde, among which styrene accounts most, at 1.1544μg/ml. VOCs from RNMP mainly are styrene, phenol and benzaldehyde, which come from resin, cross linking agent and curing agent. Styrene accounted most, at 1.2673μg/ml, 1.1895μg/ml more than the plates without NMs. The adding of NMs leads the increase of volatilization of styrene. VOCs from PMC are phenol, styrene, benzaldehyde and methylphenol, among which phenol accounts most, of 0.3795μg/ml. The adding of NMs can cause an increase of styrene and phenol volatile concentration. VOCs from WPC are complex, which include phenols, aldehydes and hydrocarbons. The aldehydes mainly are from wood, including benzaldehyde, octanal, nonanal and decanal. The concentration of all VOCs is small and the adding NMs almost has little influence on the volatilization of WPC.3. Leaching toxic and leaching law of NMs and reproduction materialsSulphuric-nitric acid method and acetic acid method were used to detect the leaching toxic of NMs and the three reproduction materials respectively according to HJ/T298 and TCLP method. According to"Identification standard of risk waste", all heavy metals leached from these three reproduction materials are much lower than the standard limit line, which means they are not risk waste and does not need special treatment; (2) the content of Cu in NMs leached by acetic acid method is 893.3 mg/L, 8 times more than the standard. So it need optimize the crushing and separation condition to reduce the Cu content in NMs; (3) the pH value of NMs increased with the leaching time and finally was at 6 while the pH of RNMPs, PMC and WPC were respectively at 8.6, 10.0 and 8.2. The increase of pH value can lead decrease in the leaching degree of heavy metals; (4) be effected by the pH and adsorption of NMs, the concentration of heavy metals increased with leaching time at the beginning and then decreased.From all above, it can be known that the recycling method of NMs as filler is safe and environment friendly.