Heavy metal ion adsorption by permeable oyster shell bricks

More than 60% of oyster shells (OS) are discarded on the beach, which pollute the soil. At 800 degrees 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. (C) 2020 The Author(s). Published by Elsevier Ltd.

Automated summary

The study found that POSB has a good adsorption effect on heavy metal ions in water, especially Ni(II), Zn(II), and Mn(II). The control of OS content, adsorption time, and water pH values is important in the manufacturing process of POSB.