High-performance electrodes for wastewater treatment
by Xueming Chen
Ph.D. Chemical Engineering
xxii, 191 leaves : ill. ; 30 cm
Electroflotation and electrooxidation are the two attractive processes in wastewater treatment. However, the lack of ideal electrodes has long been a problem. This dissertation reports two types of high-performance electrodes, Ti/lrO2-Sb2O5-SnO2 and Ti/B-doped diamond (Ti/BDD), for electroflotation and electrooxidation, respectively. 22522225222252...[ Read more ]
Electroflotation and electrooxidation are the two attractive processes in wastewater treatment. However, the lack of ideal electrodes has long been a problem. This dissertation reports two types of high-performance electrodes, Ti/lrO2-Sb2O5-SnO2 and Ti/B-doped diamond (Ti/BDD), for electroflotation and electrooxidation, respectively.
The Ti/lrO2-Sb2O5-SnO2 electrode developed in the present study was much more stable than the conventional Ti/lrO2 electrode with 97.5 percent of the precious Ir saved. The high stability of Ti/lrO2-Sb2O5-SnO2 with a low Ir content is attributed to the usage of conductive Sb-doped SnO2 as a dispersing agent, the formation of a metastable solid solution, the interfacial bonding improvement, and the compact structure of the lrO2-Sb2O5-SnO2 film. An electrode system consisting of a fork-like Ti/lrO2-Sb2O5-SnO2 anode and a Ti cathode with a similar shape has been successfully applied to electroflotation to separate oil, suspended solids, fluorides, and Cr(lV) for over one year. The Ti/lrO2-Sb2O5-SnO2 electrode still performs well for O2 evolution without any noticeable deterioration in activity.
Deposition of stable BDD films on titanium substrates is generally believed to be very difficult. In the present study, the durability of Ti/BDD electrodes has been improved significantly by optimizing the BDD film depositing conditions and using a proper organic additive. Different additives were investigated, and CH2(OCH3)2 was found to be the best one. The improved stability is attributed to the enhanced diamond nucleation and growth rates. In comparison with Ti/Sb2O5 electrodes, the generally believed very active ones, the Ti/BDD electrodes obtained have 2-3 times higher current efficiencies in oxidizing various pollutants such as acetic acid, maleic acid, phenol, and dyes. A Ti/BDD electrode prepared from the H2 + CH4 + CH2(OCH3)2 gas mixture has been used for over 300 hours, and the superior activity remains. The successful development of the stable and active Ti/BDD electrodes significantly increases the feasibility of industrial application of electrooxidation to wastewater treatment.