수산 폐자원을 이용한 비소 및 중금속으로 오염된 토양의 안정화 효율 평가

Abstract

It is known that arsenic and heavy metals such as lead, copper and zinc generated from abandoned mines have low mobility and a high accumulation rate, which can adversely affect ecosystems and humans over a long period of time. Among contaminated soil remediation technologies, the stabilization/ solidification (S/S) technology is a method of lowering the mobility and exposure risk for pollutants such as heavy metals in soil through physicochemical reactions. The S/S method is widely used to stabilize pollutants such as heavy metals in the soil by sealing, precipitation, and adsorption using an alkali-based stabilizing agent. In addition, the S/S method has been shown to be economically feasibility, efficient and prevents secondary pollution. However, industrial by-products such as cement, cement kiln dust, and fly ash which are widely used for stabilization, have not been widely applied for stabilization efforts in recent years due to contaminant content and solidification issues. Looking at the trend of research on stabilization of contaminated soil, many studies using natural waste resources such as oyster shells and starfish are being investigated. Therefore, in this study, four species of fishery waste resources mainly produced and discarded in the southwest coast of South Korea {Cockle shell (CS), Golden cuttlefish born (GCB), Brown croaker born (BCB) and Starfish (Asterias amurensis, AA)} were used to evaluate the stabilization efficiency after application to contaminated soil to confirm their possible use as stabilizing agents. The 0.1M HCl extraction method was used to evaluate the stabilization efficiency. XRF and XRD analyses were performed to see the mineralogical properties and morphology, and SEM-EDX analysis was performed to identify the stabilization mechanism. XRF analysis showed that BCB contained a lot of phosphorus (P) with CaO at 67.1% of and P2O5 at 30.9%. Furthermore, AA contained CaO at 81.3%, MgO at 7.04%, and SO3 at 4.13%. In addition, XRD analys is showed that the CS and GCB were composed of Aragonite (CaCO3). Chlorapatite (Ca5(PO4)3Cl) was the main component in BCB, and Calcite((Ca,Mg)CO3) was the main component in AA. After stabilizing the contaminated soil using the fishery waste resource stabilizers, the stabilization efficiency for arsenic and heavy metals was evaluated and showed a high treatment efficiency of 92~99% for all arsenic, lead, copper and zinc components in the case of CS. In particular, the stabilization efficiency was much higher when -#20 mesh material was used rather than -#10 mesh material. It can be seen that the stabilizers with smaller particle diameters had a larger specific surface area and thus the stabilization efficiency was improved due to smooth hydration. GCB, like CS, showed a high processing stabilization efficiency of 95-99% for both arsenic and heavy metals. However, the stabilization efficiency was higher in the case of curing for 4 weeks rather than 1 week. BCB showed a stabilization efficiency of around 70% for lead and around 50% for copper, but showed very low stabilization efficiency (less than 50%) for arsenic and zinc. Therefore, BCB was considered too difficult to use as a stabilizing agent for As and Zn. Moreover, the change in heavy metal concentrations after stabilization with respect to particle size and curing period was also not significant. AA showed a high stabilization efficiency of over 90% for all of the arsenic, lead, copper and zinc components. In particular, the stabilization efficiency was high even with a curing period of 1 week, and the stabilization efficiency was high in both -#10 mesh and -#20 mesh material applications except for zinc. After the stabilization treatment, the arsenic and copper stabilization efficiencies for each stabilizing agent was found to be in the order of GCB>CS>AA>BCB. The zinc stabilization efficiency for each stabilizer was shown to be in the order of GCB>AA>CS>BCB, and the stabilization efficiency of BCB for arsenic and zinc was less than 50%. The lead stabilization efficiency for each stabilizer was shown to be in the order of GCB>CS≃AA>BCB. As a result of analyzing the stabilization mechanism using SEM-EDX analysis, effective stabilization of arsenic by CS and GCB showed that calcium-based solubility was significantly higher as identified in several previous studies. It is thought to be due to low Ca-As precipitation. Heavy metals such as lead, copper, and zinc have a very high correlation with Al, Si, and O as identified in several previous studies, which is believed to be due to the formulation of CSHs (calcium silicate hydrates) and CAHs (calcium aluminate hydrates), which are ozzolanic reaction products. In addition, effective stabilization of lead by BCB proceeds through the formation of lead phosphate compounds such as pyromorphite (Pb5PO4)3X,X=F,Cl,OH), which is a highly stable chemical species of lead and phosphorus. A close correlation between lead and P was also confirmed in the elemental mapping analysis result, which could be associated with stabilization due to the formation of pyromorphite. Overall, it is judged that the fishery waste resource stabilizing agents applied in this study can be used as an economical stabilizing agent in contaminated soil with arsenic and heavy metals if the content is appropriately selected according to the concentration of soil contamination.