Conversion of Oyster Shell Waste to Amendment for Immobilising Cadmium and Arsenic in Agricultural Soil

摘要

A bulky waste, oyster shell (OS), was calcinated at 400-800 degrees C to produce Ca-rich products (OS400-OS800) to reduce the human health risk of soil cadmium (Cd) and arsenic (As). Thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET method were used to characterize OS and its calcined products. OS and OS400-OS(700)removed little Cd and As from water, whereas OS(800)removed 1508 mg Cd or 514 mg As per kg of OS(800)from solutions of 1032 mg Cd/L or 257 mg As/L via adsorption and precipitation. Adding OS(800)at a 2% dose to a Cd- and As-contaminated soil lowered its exchangeable Cd from 60% to 27%, and reduced Cd content in the edible part of vegetable Bok Choy from 2.80 to 0.048 mg/kg and As from 1.73 to 0.47 mg/kg. Converting OS to soil amendment has the dual benefits to soil remediation and sustainable oyster aquaculture.