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In recent years, some researchers in China have conducted supercritical water oxidation experiments on organic wastewater such as alcohols, phenols, benzene, nitrogen and sulfur, and achieved satisfactory results
.
Some researchers have conducted preliminary explorations on the supercritical oxidation treatment of high-concentration fermentation wastewater.
2.
4.
1.
1 Degradable polystyrene foam
Polystyrene foam has the advantages of light weight, non-toxicity, heat insulation, shock absorption, etc.
, so it is widely used.
However, polystyrene foam is thrown away after use and becomes garbage, and it is not easy to be decomposed by microorganisms.
It accumulates and causes harm to the environment.
, Which is commonly referred to as "white pollution"
.
So far, the main methods for processing and recycling waste polystyrene foam are:
①Buried;
②Incineration and use of its thermal energy;
③Extrusion granulation;
④ Thermal decomposition into gas and liquid;
⑤Solvent dissolves to make paint or adhesive
.
The landfill method requires land occupation; the incineration method generates a lot of black smoke and some toxic gases; other methods have achieved certain results, but the polystyrene foam must be sorted and cleaned before disposal, which requires a lot of work
.
In addition, the thermal decomposition method requires high temperatures, which can cause carbonization and block pipes
The research on the degradation of waste plastics (mainly polystyrene) by SCWO began in the 1990s, and its purpose is mainly to overcome some of the shortcomings of thermal degradation (easy to form carbon and low yield of styrene)
.
The method has extremely high efficiency.
Domestic scholars have carried out supercritical water oxidation technology to degrade plastic experiments.
Under the conditions of temperature 400~450℃, pressure 23~35MPa and reaction time 60~120min, supercritical water can effectively degrade polypropylene; within 1h at 380℃ The polystyrene is completely degraded, and the mixed plastic of polystyrene and polypropylene can be completely degraded at 390°C and 1h; at a temperature of 400°C and a pressure of 34MPa, after 30 minutes of reaction, the polyethylene foam in supercritical water can be completely degraded.
The molecular weight can be reduced by about 98%
.
Foreign scholars conducted supercritical water oxidation experiments on polyethylene at 425°C, 120min, and a water/polyethylene ratio of 5, and the polyethylene was decomposed into oil