Improved separation performance of SS fiber nonwoven felt by the coating of a non-isotropic porous SS membrane layer

With excellent mechanical properties, large porosity, and permeability, stainless steel (SS) fiber nonwoven felt has outstanding application advantages in high-temperature filtration and purification. However, the pore size of the SS nonwoven felt, which is directly determined by the diameter of the produced fiber stacked inside, usually varies from tens of microns to several microns. Low filtration accuracy greatly limits its application in the fields of fine separation and purification. In this study, the separation performance of SS fiber nonwoven felt was improved by the coating of a non-isotropic porous SS membrane layer via the immersion precipitation phase inversion-sintering method. The effects of sintering temperature on pore structure, surface wettability, separation performance, and mechanical properties of the coated SS nonwoven felt were characterized by scanning electron microscope (SEM), water contact angle (WCA), water permeability, and tensile test, respectively. The results suggest that with the increase of sintering temperature from 1000°C to 1200°C, both porosity and pore size reduce gradually. The WCA value shows an increase from 31.4 to 62.3° and pure water flux shows a corresponding decrease from 2562 to 889 L . m ⁻² . h ⁻¹ . The sintering temperature has a negative effect on the mechanical strength of the coated SS fiber nonwoven felt, which is mainly determined by the mechanical properties of the sintered SS fiber nonwoven felt substrate. The coated SS fiber nonwoven felt exhibits a long-term durable separation performance even after frequent combined physical washing and chemical cleaning when applied in the treatment of potato starch wastewater.