Intensification Of Foam Drainage By Corner Effect And Its Application In Recovery Of Silk Proteins By Using Foam Fractionation

Foam fractionation is a promising green concentration method,and its foam drainage process has attracted increasing interest of researchers in recent years.Lu et al.had studied the “wall effect” on foam drainage and the experimental results indicated that the drainage rate of the interstitial liquid in the exterior channel(Plateau borders constructed by two intersecting films and the column wall)was higher than that in the interior channel(Plateau borders constructed by three intersecting films).In order to further strengthen the foam drainage and achieve the high enrichment of the desired material,the exterior channels could be further divided into wall channel and corner channel.Thus,“corner effect” was presented in the current work based on the “wall effect”.Firstly,the mechanism of foam drainage enhanced by “corner effect” during foam fractionation was investigated.Then,a novel column with groined internal component(GIC)was developed and used to separate silk sericin from the filature wastewater and silk fibroin from the waste silk.Considering the perspective of solid-liquid contact area,it is found that during foam fractionation,the more the liquid contact area in the formed foam drainage channels with the wall surface was,the better the drainage effect should get.The experimental results showed that the liquid holdup of the foam in the component with the corners effect was significantly lower than that in the inner sleeve component with only wall effect(have the same wall area).The theoretical analysis was consistent with the experimental results.Using bovine serum albumin as the desired material,the effects of corner numbers,the concentration of BSA and volume air flow rate on the superficial liquid velocity were investigated,respectively.Experimental results suggested that the “corner effect” could be used to reduce the liquid holdup of the foam by decreasing the superficial liquid velocity of entrained liquid inside the foam.The internal component with a suitable length of 400 mm,and a corner dimension of 90° could significantly strengthen foam drainage when it was mounted at the location of 40 mm from the top of the column.The novel foam fractionation column with groined internal component was applied to recover silk sericin from the filature wastewater.Experimental results indicated that p H and temperature had played a critical role in determining the performance of foam fractionation.Under the suitable operation conditions of p H 4.0,temperature 40°C,volumetric air flow rate 150 m L/min,and pore diameter of gas distributor 0.180 mm,the enrichment ratio and the recovery percentage of silk sericin reached 6.77 and 80.29%,respectively.The molecular weight of sericin was 16 k Da by sodium dodecyl sulfate polyacrylamide gel electrophoresis.In order to recover silk fibroin from the scraps of silk-reeling industry,GIC was applied to strengthen foam drainage.The experimental results showed that the GIC could effectively strengthen foam drainage of the solution with high viscosity,the suitable condition for extracting silk fibroin from the scraps of silk-reeling industry was calcium chloride concentration of 40%,temperature 90°C,dissolving in an hour.Under the suitable operation conditions of p H 5.0,temperature 25°C,volumetric air flow rate 300 m L/min,and pore diameter of gas distributor 0.180 mm,the enrichment ratio and the recovery percentage of silk fibroin reached 5.41 and 82.30%,respectively.Sum up,corner effect could effectively strengthen the foam drainage and improve the performance of foam fractionation.This work is expected to provide a cost-effective technique by using GIC to recover silk sericin from the filature wastewater and silk fibroin from the scraps of silk-reeling industry,and to promote the industrialization of foam fractionation in wastewater treatment.