Direct current electrochemical method for removal and recovery of heavy metals from water using straw biochar electrode

Treatment of heavy-metal pollution in industrial wastewater is critical in protecting human health and the environment. Current methods for heavy-metal treatment have many limitations. For large quantities of industrial wastewater, the common methods such as adsorption and chemical precipitation can not meet the needs of actual production because of their high cost and limited removal efficiency. Electrochemical deposition is a rapidly developing clean treatment technology in recent years. The preparation of good electrode materials is one of the keys to the development of this technology. Firstly, by adjusting the pyrolysis temperature, rice straw was transformed into conductive biochar at 900 °C and CO2 atmosphere; then, we proposed a new concept of electrode preparation, that is, straw biochar electrode was prepared by thermosetting method. In this innovative method, a three-dimensional circular straw biochar electrode with high strength was successfully prepared by thermosetting method, phenolic resin as molding agent and conductive straw biochar as main raw material; using the electrode as cathode, cadmium polluted wastewater was treated by DC electrodeposition. The preliminary experimental results show that when the current density is 7.80 mA/cm2, the removal rate of cadmium in the solution reaches 76.60% in 240 min. Furthermore, the electrode is separated from cadmium by acid pickling to realize the effective recovery of cadmium and electrode regeneration. After regeneration, the removal rate of cadmium still reached 74.16%. Our work is very important for the treatment of cadmium ion pollution in water. The electrode can directly and effectively removes cadmium ions from wastewater. After pickling, the deposited cadmium can be effectively separated from the electrode, and the separated electrode can continue to be recycled. This study provides a simple and clean method for the treatment of cadmium containing wastewater, which can effectively reduce the cost of treating heavy metal wastewater by electrochemical deposition, and has important research and industrial significance.