Walnut shell filter materials has strong adsorption and contaminants interception ability, anti-oil immersion, high hardness, good wear resistance and stable chemical properties, its surface was easily polluted by the absorbed crude oil in oily sewage to reduce its filtering and backwashing effect. The surface modification of the walnut shell was the introduction of hydrophilic groups to enhance its hydrophilic oleophobic property; Used different ratio of sulfite to boil the walnut shell at a certain temperature to make a modification on the hydrophilicity of walnut shell surface, the modified filter materials with varying degree of surface modification was obtained. Measured the contact angle between walnut shell and water, the wetting performance was significantly improved, the contact angle was decreased from 95° to 36.75°, the surface properties were changed from lipophilicity to hydrophily. the micropores of surface become smaller, and it was conducive to the accumulation of emulsified oil beads; After filtration treatment of oily wastewater containing polymer, filter oil removal rate was over 78%, the oil removal rate of the modified filter materials was increased by 25% than that of the unmodified filter materials, and oil content in the filtered sewage was below 45 mg/L, the backwashing oil removal effect of modified filter materials increased from 17% to 87%, intercepted oil in the before process of filtration was more easier removed in the after process of backwashing to make the filtering performance regeneration of walnut shell filter materials. In the case of filtration treatment on the same amount of oily sewage its lifetime could be extended more than twice.
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