1aboutSPGbubble

“SPGBubbles "are a type of gas that transfers pressure from a gas sourceSPGThe method of dispersing from the micropores of the membrane; Generally speaking, very small bubbles in liquids are called "fine bubbles", with a size of1-100μmThe bubbles are called "microbubbles" and are smaller than1μmThe bubbles are called 'nano bubbles'.

SPGThe characteristic of bubbles is to changeSPGThe pore size of the membrane is used to change the size of bubbles, and it is also suitable for generating larger millimeter sized bubbles from microbubbles; In addition,SPGBubbles are a "very static generation method" that does not require strong liquid flow or pressure on the liquid itself. They can provide small bubbles without damaging the microorganisms and macromolecules in the liquid, or utilize the principle of bubble suspension.

IISPGbubble pressure

SPGThe bubble pressure of the membrane varies greatly with the pore size, and the smaller the pore size, the higher the pressure at which bubbles are generatedSPGThe pressure at the "bubble point" where the liquid is squeezed out of the membrane pore is equal and can be calculated.

PB= 2γ ●cosθ/ R

PBBubble point pressure;

γSurface tension between gas and liquid phases

θThe contact angle between the membrane surface and the liquid phase.

R：SPGpore radius

The following table and chart calculate the pressure when air bubbles in water.(γ= 72.75mN/m、θ=30°)

●due toSPGSpecialized module(Fixed fixture)We recommend usingSPGThe pore size of the membrane is0.3μmabove,Simultaneously under pressurecanControl inless than1MPafollowing; bubblepressurecanfollowSPGThe specifications of the moduleoccurchangeAnd it will also followSPGThe aperture changes.

●The significant variation in pressure depends on the surface tension and viscosity of the liquid used；The smaller the surface tension, the greater the pressurecome nearThe lower.

●The above values are the pressure required to squeeze the liquid in the pores，Once the liquid is squeezed out, the gas passes throughSPGPores and bubbles will form at lower pressures；onceminuteIf the liquid in the hole is squeezed out, it willformSmall bubbles, fromSPGporecentrecontinuousReal estate production，after thatAdjust by reducing the pressure while checking the status of the bubbles.

●SPGgasThe mechanism of foaming is whenSPGsurface(Including the interior of pores)When soaked by liquid, due to the effect of surface tension, gasSPGsurface(Export)Formation on top“bubble”The contact angle with the gas increases，Therefore, if there are substances that repel liquids adhering toSPGOn the membrane, if the surface condition is not wetted by liquid, it cannot be obtainedidealThe performance can cause the generation of large bubbles.

IIIThe relationship between SPG membrane pore size and bubble size

SPGgasThe characteristic of bubbles is to changeSPGThe pore size of the membrane is used to control the size of bubbles，according toKukizakiThe doctoral research, when0.3 wt%ofSDS(Anionic surfactant)Adding water, there are reports thatDp(bubble size)=Dm (SPGmembrane pore size)x8.6，However, bubbles are very unstable, and it is said that when the size of the bubble is50μmAt that time, small bubbles self contract due to internal pressure，On the contrary, larger bubbles will expand，Therefore, the actual size of bubbles depends on the type of liquid used(surface tension)The type of gas used(Solubility)Generate environment(Surface of membrane devicePressure, etc)And the residence time in the liquid.

thereforeDp = DmxN，We believe it is necessary to determine each relationship based on the purpose and method of use，The size of bubbles is greatly affected by the surface tension of the gas-liquid mixture. If the surface tensionget overBig, with bubbles as wellget overIf a surfactant that reduces surface tension is added to water, orpersonAlcohol easily produces small bubbles.

▲ SPGmembrane pore size(Dm)Can control the diameter of bubbles(Dp)： Dm large=Dp large, Dm small=Dp small

▲Gas-liquid surface tension：big=high pressure= DpBig, small=low pressure= Dpsmall

▲Bubble floating speed：DpSlow down,DpBig Quick

▲Gas-liquid contact area(Bubbles with the same volume)：Dpsmall=Big,Dpbig=small

▲Microbubbles and millimeter bubbles are both unstable and do not maintain a certain size：Dp 50umbelow=Contraction,Dp 50umthe above=inflate

4Quantity of foam generated

basicallySPGBubbles are controlled by pressure to achieve optimal conditions for bubble generation，This is because of pressureDecline ofhappen inSPGPore size of the membraneinternalSo the flow rate of gas can only be controlled by pressure；At this point, the amount of gas permeation depends on the liquid and gas used, butSPGThe effectiveness of the membranegasBubble area is directly proportional，If you double the usageSPGThe length of the membrane(area)The number of bubbles generated will also double.

useSPGMembranous type: filmpipeφ10mm，length(Length)L105mm

*Even if the pressure is increased to increase the flow rate, only large bubbles will appear and no fine bubbles will be produced.

5withinPressure methodAnd outsidePressure method

Adopting high-strength pipe type10mmSPGfilmpipehave“Internal pressure”and“external pressure”Two uses, according toSPGThe method of fixing the membrane andSPGThe strength derived from the shape of the pipeline,actualThere is a significant difference in work pressure.

Internal pressure external pressure

Gas fromSPGPressurizing the inner surface of the tube generates bubbles on the outer surface，Gas fromSPGThe outer surface of the tube is pressurized, generating bubbles on the inner surface,

Its characteristic is that bubbles are easily dispersed in the liquid while the liquid does notflowmove. It is necessary to forcefully transport the liquid to the inner surface of the pipeline, and the liquid flows inside the pipeline.

*1:The maximum pressure varies depending on the module used.

*2:In the2Page of“gasBubble pressure”Determine based on the pressure usedSPGRecommended aperture size. When using liquids with lower surface tension, smaller ones can be usedSPGAperture.