Pollution and migration characteristics and potential ecological risk assessment of heavy metals in waste circuit boards recycling process
The annual generation of waste printed circuit boards(WPCBs)has increased over the last decade due to the rapid development of the electronic information industry and the acceleration of the replacement of electrical and electronic products.While waste printed circuit boards(WPCBs)have high recycling values,their recycling can also pose a threat to ecological safety and human health due to the presence of harmful heavy metals such as Pb,Cd,and As.Therefore,researching the pollution and migration characteristics of heavy metals in the recycling process of WPCBs can provide a foundation for precise pollution prevention and control measures for protecting both human health and environmental safety.In this study,a WPCB recycling enterprise,which mainly uses defective WPCBs,with mechanical separation was taken for the research object,environmental media samples of dust,total suspended particulates(TSP)and soil were collected.The enrichment factor and geo-accumulation index were used to evaluate the enrichment and pollution characteristics of heavy metals,and statistical analysis methods such as Pearson correlation analysis,and principal component analysis were used to expound and reveal the migration regularity in the recycling process.Additionally,a comprehensive potential ecological risk index(RI)was used to estimate the potential ecological risk of heavy metals.It showed that the concentration of Cu was the highest and Cd was the lowest in dust and TSP in the workshop.Sn,Cu,Pb,Cd and Zn showed varying enrichment in both dust and TSP.When compared with distribution mainly in dust,Sn,Cd,and Pb were predominantly distributed in TSP.While,the impact on the environment outside the workshop of Sn,Cu and Pb in TSP was demonstrated rarely limited.Due to different properties and morphology in particles,Cu,Pb,Sn and Cd expressed different migration characteristics.In general,the migration characteristics of heavy metals in WPCBs recycling were presented as follows:crushed WPCBs with small particle size-TSP in the workshop-dust in the workshop and TSP outside the workshop-surface dust or soil-flying dust-TSP.The RIs of dust and TSP in the workshop were 386 and 1706,respectively,among which Cu,Cd and Pb contributed more.Therefore,several measures for managing and controlling pollution caused by heavy metals were proposed for recycling enterprises.These measures include the proper disposal of cleaned dust within the workshop,utilizing a closed and slightly negative pressure workshop,and installing a set of gas collection and treatment facilities.
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