Electrochemical technologies combined with physical, biological, and chemical processes for the treatment of pollutants and wastes: A review

Many electrochemical techniques for the remediation of water and soils are successful as stand-alone technologies. These include electrooxidation ( EO ), electroFenton ( EFent ), electrocoagulation ( ECG ), electroflocculation ( EF ), electroflotation ( EFlot ), electrodehalogenation ( EDehal ), electrochemical disinfection of water ( EDis ), electrochemical ion exchange processes ( EIX ), electrochemical removal of metal ions ( EM ), photoassisted electroremediation ( PE ), coupled anodic and cathodic processes and electrokinetics ( EK ), among others. These are even more powerful when coupled to other non-electrochemical technologies (i.e., physical, biological, or chemical) such as irradiation (including ultrasound ( US ), ultraviolet ( UV ), or visible light), biocatalysis, adsorption, filtration, chemical oxidation, advanced oxidation processes ( AOP ), and ozonation, among others, or to other electrochemical technologies. The advantages and challenges encountered in such combinations constitute the subject of the present review. In some cases, synergistic effects are observed. Therefore, synergy figures of merit are defined and discussed. • The toxicity of chemical species can decrease because of changes in mobility, solubility, size, geometry, or standard potential. • Oxidation and reduction processes at electrified surfaces are used for the solution of many environmental problems. • Some limitations can be overcome by combination with physical, biological, chemical, or other electrochemical technologies. • Synergistic interactions occur in some combined processes, which need to be evaluated by appropriate figures of merit.