Diphenylguanidine Production Wastewater: Advanced Ozone Catalytic Oxidation
Diphenylguanidine (DPG) is an important accelerator in the rubber industry, where it activates thiazole, thiuram and sulfenamide accelerators. It is widely used in tyres, rubber sheets, rubber footwear and other rubber products and has played a significant role in the development of the industry. Its production, however, generates large volumes of wastewater with extremely high pollutant concentrations: COD above 10,000 mg/L, total nitrogen above 9,500 mg/L, ammonia nitrogen above 8,500 mg/L and conductivity above 50,000 (expressed as mg/L in the source data). Discharged without pretreatment, such wastewater places a severe load on the downstream treatment system.
The Treatment Challenge
Faced with this problem, a large chemical company in China once considered the Fenton process, but high operating cost, complex operation and potential safety risks made the scheme impractical. An efficient, economical and safe treatment process was urgently needed.
Against this background, SINOKLE proposed a new solution based on its independently developed CDOF advanced ozone catalytic oxidation technology.
Process Description
CDOF combines rigorously selected heterogeneous ozone catalysts with fine-bubble dispersion of ozone gas created by high-speed shear in the water flow, which achieves efficient ozone dissolution. Dissolved ozone molecules are rapidly converted into highly oxidizing hydroxyl radicals (OH, oxidation potential 2.8 V) under the multiple catalytic action of the heterogeneous solid catalyst. These radicals progressively oxidize organic matter into water and carbon dioxide, effectively lowering COD and colour.
In practice, the DPG wastewater is first lifted by an ozone dosing pump into a high-efficiency ozone dosing unit. After efficient ozone dissolution the wastewater enters the primary CDOF main catalytic reactor, where ozone molecules are converted into hydroxyl radicals that oxidize and break down organic matter. The flow then enters the CDOF secondary reaction stage, which integrates ozone catalytic oxidation with flotation to oxidize the remaining organics. The effluent passes through a high-efficiency coagulation and sedimentation tank, where flocculant and coagulant aid are added; after sedimentation COD falls below 1,500 mg/L and colour is removed.
Results and Economics
With the two-stage CDOF integrated ozone oxidation and flotation units plus coagulation and sedimentation, COD of the DPG wastewater dropped from more than 10,000 mg/L to below 1,200 mg/L and the colour was eliminated, fully meeting the owner's requirements. The effluent is then sent to downstream biological treatment and evaporation for final discharge compliance.
The economics are equally attractive. The total treatment cost, including chemicals, liquid oxygen and power, is about RMB 45 per tonne of water — far below the roughly RMB 200 per tonne of the original conventional process. The technology is also compact and highly automated: the facility occupies only about 230 square metres, saving valuable production space.
In summary, applying CDOF advanced ozone catalytic oxidation to DPG wastewater solves the problems of poor performance, high operating cost, complex operation and safety or environmental risk associated with conventional processes, while saving the company substantial expense and floor space. The successful application supports the sustainable development of DPG producers and brings new momentum to the environmental protection industry.
