1. Field of the Invention
The present invention relates to a method to prepare un-hardened ceramic micro-electrolysis fillers by industrial solid wastes, which belongs to wastewater treatment field especially high-concentration refractory wastewater pretreatment field.
2. Description of the Related Art
Since 1960s, with the rapid development of chemical industry, a large number of synthetic organic materials were produced industrially, such as rubber, plastic, nylon, macromolecular, synthetic fiber and so on. During the production process of these organic materials, a large amount of high concentration organic wastewater was produced. According to Global Environment Statistics Bulletin, in China, 44.3% of total wastewater emission was industrial organic wastewater up to 2008 years. The components of the industrial organic wastewater is complicated which main contained aromatic compounds, heterocyclic compounds, sulfide, cyanide and heavy metal and so on. Even, some of the organics had strong carcinogenicity, mutagenicity toxicity and were difficult to be biodegraded which were extremely harmful to human health and environment. Traditional methods of treatment and pretreatment had high costs or lacked mature faultiness technological ways. Therefore, they could not be used widely.
In nature, the reserves of lignin was next to cellulose and 5 million tons lignin was regenerated annually. In pulping and papermaking industry, 140 million tons cellulose was separated from plants, and 50 million tons lignin was produced as by-product. But over 95% lignin was burned after condensation or discharged into rivers as black liquor. The reuse of lignin became the problem of people's attention. Scrap iron, a kind of common solid waste, was mainly generated from mechanical manufacturing industry and had a high production which not only occupied the valuable land resources but also polluted the environment. How to reuse the iron scrap were widely studied. Red mud was produced by aluminium industry which was harmful to environment. When 1 ton aluminium oxide was produced, 1-2 ton red mud was generated as by-product. As the fourth largest alumina production in the world, millions tons of red mud were discharged in China. Because pH of red mud lixivium was high which could reach 12-13, red mud belonged to hazardous waste. In China, red mud usually piled up in the past which not only occupied the land resources but also lead the soil, water and air pollution. Thus, treatment and recycling of red mud became the global environmental issues.
The micro-electrolysis technology, which is also called internal-electrolysis, is effective way to treat high concentration, high chroma, high salinity and refractory organic wastewater. When the micro-electrolysis fillers were soaked into wastewater, numerous macroscopic galvanic cells formed because of the potential difference between iron and carbon. In the galvanic cells, iron was anode and carbon was cathode. Contaminant was degraded in acid solution through electrochemical reaction. Micro-electrolysis technology was introduced into China in 1980s. And in recent years, it has been widely used in the wastewater treatment, such as printing and dyeing wastewater, pharmaceutical wastewater, pesticide wastewater and so on. In addition, micro-electrolysis technology had some advantages such as low cost, easy operation and maintenance. During the running of traditional micro-electrolysis process, the contact area between the sewage and the padding could be reduced due to the fillers hardening, which decreased the removal efficiency of wastewater and increased frequency of backwash and fillers replacement. This is the limit for micro-electrolysis technology to widely used. However, ceramic micro-electrolysis fillers had better performance on un-hardening than traditional fillers.
During productive process of traditional micro-electrolysis fillers, activated carbon or charcoal was added as cathode material. Activated carbon and charcoal were stable and did not generate gas, so the density of fillers was high. In addition, activated carbon and charcoal were produced by sintering. So it lead to energy waste to use activated carbon and charcoal sinter micro-electrolysis fillers.