Laboratory scale study of an industrial phosphate and thermal treatment for polluted dredged sediments

Dredged sediments are being chemically treated with phosphoric acid on an industrial scale. The effectiveness of the treatment was evaluated by performing the chemical reaction in a tubular reactor, followed by convective drying and maturation of the treated sediment at ambient temperature and finally thermal destruction of the organic matter by calcinations (500°C–900°C). The influence of acid concentration and calcination temperature on the specific surface area of the sediment was investigated. The stabilization of the heavy metals was evaluated by leaching tests and sequential extraction procedures. The phosphoric acid treatment is effective in reducing heavy metal mobility, a prerequisite for recycling the sediments in various construction materials.