The process and mechanism of dirt interception by walnut shell filter

The dirt interception process of the walnut shell filter material and the nature of the trapped dirt mainly include the following aspects: (1) The sedimentation fouling formed by the suspended particles deposited on the surface of the filter material under the action of gravity: the denser suspended impurities in the oil production wastewater are caused by gravity. Under the action of the filter material, it is continuously deposited on the surface of the filter material, and the resulting dirt has weak adhesion on the surface of the object and is easy to remove from the surface of the filter material. The main thing that is removed by the hydraulic backwash method is this kind of dirt. (2 ) The dirt attached to the surface of the filter material under the action of physical adsorption or adhesion: this type of dirt is mainly oily, and due to its hydrophobicity, it is easy to adhere to the surface of the filter material particles. In the walnut shell filter, oil The particles adhere to the fine suspended particles, and adsorb on the surface of the filter material to form dirt. This form of attached dirt is often difficult to remove by hydraulic cleaning due to its hydrophobicity. (3) Attached to the filter material under the action of electrostatic attraction Surface dirt: When the suspended particles in the wastewater and the surface of the filter material have opposite charges, they will be adsorbed to the surface of the filter material under the action of electrostatic attraction; negatively charged dirt particles and the same negatively charged filter surface can also be The high concentration of positively charged metal cations condense on the surface of the filter material to form dirt. Under the condition of hydraulic recoil, this type of dirt can be removed to a certain extent depending on the strength of the action or bonding strength with the surface of the filter material (4) Diffusion that penetrates into the internal pores of the filter material: The walnut shell filter material has a certain pore structure. Due to the diffusion effect, the pollutants and impurities in the water will migrate to the inside of the filter pores. It can be found from the scanning results of the electron microscope. After the filter material is intercepted, the original pores are obviously blocked. If only by hydraulic cleaning, the dirt in the pores cannot be removed, and the walnut shell filter material cannot be restored due to its porous properties, resulting in the ability to intercept dirt. Reduce. After cleaning with chemicals, both the surface of the filter material and the pores of the filter material can basically be restored to the state before the dirt interception.