Hydrofluoric acid and chromium chloride wastewater treatment

The chromium ion and hydrofluoric acid wastewater generated during the production process, if discharged without treatment, can cause severe pollution to the surrounding environment and water sources of the factory area, posing harm to both society and the factory itself. Our company has developed a novel wastewater treatment process specifically for fluoride and chromium-containing wastewater, which not only meets emission standards but also significantly reduces operating costs. By adding decolorizers and defluoridizers to the wastewater, the treated wastewater can be discharged with a pH of 6~9 and a fluoride ion concentration of less than 10ppm. This process effectively removes chromium ions and meets the requirements of the Integrated Wastewater Discharge Standard. 
Technical Background 
Passivation treatment is often required in the manufacturing and processing of many mechanical equipment and their components. Passivation solutions typically contain chromium ions, hydrofluoric acid, etc. To ensure the quality of passivation treatment, it is necessary to replace the passivation solution regularly. Both chromium ions and hydrofluoric acid are harmful substances. If discharged without treatment, they can cause serious pollution to the surrounding environment and water sources of the factory area, which is harmful to both society and the factory itself. Therefore, it is of great significance to seek an effective process method for treating this wastewater. 
Technical Introduction 
Currently, the commonly used methods for treating fluoride- and chromium-containing wastewater both domestically and internationally can be broadly categorized into two types: precipitation and adsorption. Chemical precipitation involves adding chemicals such as calcium salts to form a precipitate or allowing them to be adsorbed onto the precipitate formed, resulting in co-precipitation. This method is simple, convenient to handle, and cost-effective. However, due to the low solubility of lime, it can only be added as an emulsion, and the resulting CaF2 precipitate coats the surface of Ca(OH)2 particles, preventing their full utilization, thus requiring a large amount. The fluoride content in the treated wastewater can generally only be reduced to 15mg/L, making it difficult to meet the national standard for Grade I. Furthermore, there are disadvantages such as slow sedimentation of sludge, difficulty in dewatering, long treatment cycles for high-flow emissions, and unsuitability for continuous treatment and continuous emissions. 
Adsorption refers to the process where fluoride and chromium-containing wastewater flows through a contact bed, undergoing ion exchange or chemical reactions with the solid media in the bed to remove fluoride and chromium ions. This method is only suitable for low-concentration fluoride and chromium-containing wastewater. Furthermore, the regeneration of the contact bed and the treatment of high-concentration regenerant are indispensable parts of the entire operation process. The frequent regeneration of the contact bed leads to higher operating costs. 
Our company has developed a new wastewater treatment process for fluoride and chromium-containing wastewater, which not only meets emission standards but also significantly reduces operating costs. 
The current composition of the wastewater is: HF, H2SO4 (normally 1%) (10% during centralized treatment every month), potassium fluotitanate 1‰, sodium molybdate 2‰, chromium chloride 2‰, sodium nitrate 2‰, PH=2, with a normal treatment capacity of 3-4t/h. During peak periods, the daily wastewater volume reaches 108.96t, and the average treatment capacity is calculated at 4.54t/h. The acidity during peak periods is 1.3-1.4 times higher than usual. 
Adding decolorizers, defluoridizers, etc. to the wastewater can ensure that after treatment, the wastewater has a pH value of 6~9 and a fluoride ion concentration of less than 10ppm. It can also remove chromium ions, meeting the requirements of the "Integrated Wastewater Discharge Standard". 
Technical Features 
Relevant experiments can be conducted for different types of wastewater to fully demonstrate feasible wastewater treatment solutions. After experiments and relevant calculations, a scheme design can be made to facilitate reasonable equipment selection. While meeting customer needs, the one-time investment in the project can be minimized. Through the reasonable selection of processes, the operating costs of the project can be kept within a reasonable range. 
Scope of application 
Wastewater treatment for passivation wastewater and other fluoride and chromium-containing wastewater generated during the manufacturing and processing of mechanical equipment and its components.