Study On The Optimation And Mechanism Of Buoy-bead Flotation For Harvesting The Chlorella Vulgaris

The biotechnology goes into blossom nowadays,Chlorella vulgaris?C.vulgaris?was regarded as the representation of new type crops.It could not only provide food for human being as traditional crops,but also acted a pivot role in cleaning power as an ideal ingredient,supporting the development of all kinds of industries.The harvesting was the key process in converting the C.vulgaris into productions,while it was also restricted because of the high cost.In order to improve the recover and lower the harvesting cost,this study focused on an innovative harvesting method,namely buoy-bead flotation,studying the mechanism of both the algae and beads in the harvesting.According to the different materials of beads,we inferred a factor for screening the beads.What's more,eight factors that may impact the buoy-bead flotation was analyzed to judge their significance.With regard to the significant factors,adjusting them to reach the best recovery by response surface method.The study indicated that:1)The material of beads influence significantly in harvesting the C.vulgaris,sodium borosilicate,flyash,glass,latex showed obvious recovery,and sodium borosilicate was the best among them.Nevertheless,the expanded plastic almost could not recovery any algae.After treating by acid,all beads showed better recovery,besides,the recovery of the flyash got the fastest increased.2)According to the extended Derjaguin-Laudau-Verwey-Overbeek?xDLVO?theory,the conditions in the boundaries of between different kinds of beads and the C.vulgaris were studied,the secondary minimum was found in d=17nm in the sodium borosilicate-C.vulgaris boundary,while it was not found in other conditions.This secondary minimum indicated that the beads made by sodium borosilicate and the algae could cohesion with each other in the certain distance.In this way,alge could be carried by bead and then up to the top of the solution,achieving the harvesting.The surfaces of beads made by sodium borosilicate or glass were hydrophilic,while that of beads made by flyash or latex were hydrophobic.3)Based on the expressing of hydrogen layer between the bead and the algae cell,a factor was inferred for helping screen the different materials of beads,=1/?1-cos?,in whichindicated the recovery of the C.vulgaris,the lower value was supposed to indicate the better buoy-flotation recovery.The experiment results proved th factor could predict a material was effective for C.vulgaris4)Among the factor which may impact the buoy-bead flotation,to be explicit,these factors including the pH value,temperature,dimeter,beads concentration,time,speed of agitator,concentration of chitosan or tea saponin.The results of the Plackett-Burman design experiment pointed out that the dimeter,beads concentration and speed of the agitator had significant influence towards the recovery.5)Among the three significant factors,the recovery responded to the dimeter sensitively.The recovery?Y?response equal with the beads concentration?X₁?,the speed of the agitator?X₂?,and the dimeter?X₃?was showed as follow:Y=0.83+0.035X₂+0.00995X₃-0.023X₁X₂+0.071X₂X₃-0.062X₁²-0.096X₂²-0.2?3₃²?After handling by the least square method,the optimal condition for recovery was predicted within 0.546g/L beads concentration,the speed of the agitator in133rpm and the dimeter of 56um.The subsequent experiment results proved the prediction fit to the actuality well.6?Comparing to the conventional methods for harvesting the C.vulgaris,the buoy-bead flotation had advantages in both economy and technology.Within the harvesting process,there was no secondary pollution,and the beads could be used sustainably.This innovative technology satisfied the demands of the industry.