Heavy metal ion adsorption by permeable oyster shell bricks: Fid-Bau Portal

Heavy metal ion adsorption by permeable oyster shell bricks

Xia, Chunhua / Zhang, Xueying / Xia, Linghui

Highlights • The calcined structure of oyster shells and adsorption mechanism were summarized. • Key points for improving the production process of POSB were described. • The content, time and pH effect of adsorption of heavy metal ions by POSB were analyzed. • The electrostatic complexation, ion exchange and chemical precipitation were discussed. • The adsorption effect of POSB on wastewater treatment was simulated.

Abstract More than 60% of oyster shells (OS) are discarded on the beach, which pollute the soil. At 800 °C, OS completely cracks into calcium oxide (CaO), which has the physical adsorption characteristic of a mesoporous structure. The permeable oyster shell bricks (POSB) used for purifying water were made by improving the process with OS as an aggregate. The adsorption effect on heavy metal ions in landscape water under different OS contents, adsorption times and pH values was investigated by using POSB via atomic absorption spectrometry. The results show that the optimum OS content for the standard weight (2.5 kg) POSB is 515–525 g, and the effect of the adsorption of nickel (Ni(II)), zinc (Zn(II)) and manganese (Mn(II)) were Ni(II) > Zn(II) > Mn(II) in the water environment with pH values of 7.5–7.9 for a long time period (>22 h). However, the adsorption effect of trace copper (Cu(II)) was not significant at the same time. The mesoporous structure of CaO has coordination centers and hydroxyl functional groups that have a strong adsorption effect on Ni(II), Zn(II) and Mn(II) to form complexes in the alkaline environment, and microscale Ca(II) can exchange ions with Ni(II), Zn(II) and Mn(II) to produce chemical precipitates. POSB were used in the simulation of sidewalks, squares and the revetment of a park. The experimental results show that the POSB of the revetment absorbs a larger amount of heavy metal ions than others due to a longer soak. The result shows that the POSB has a continuous adsorption effect and has great potential for wastewater treatment.