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Bench scale nanofiltration setup

I finally recieved a suitable (I think) pump, Ismatec Reglo Z, which is a magnetic drive pump that can handle up to 6 bar or so. Initially I had much trouble with leaks, and still have. The Jasco fittings seem to be self sealing though, so they are no trouble, but the manometer NTP fitting is leaking and I can’t seem to stop it, but it is now slowed down to a drip.

The permeate is collected in a flask which  I placed on a analytical scale to measure the permeate flow, while the reject is recirculated back to the reservoir. The setup can be seen in the pictures below.

At present the system is running untreated surface water at:

• 4 bar, reject flow
• 90 ml/min
• permeate flow 2.5 ml/min.

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Getting the right pump - how hard can it be?

The Sterlitech pump flow rate was about 20 l/min or so, way too much. And as a result the pressure were uncontrollable, resulting in water leaks all over.

I finally managed to convince Sterlitech to return the faulty pump they sent me, and to have them pay the horrendeous shipping cost to.  I also found another pump that should work just fine for our purpose, namely the  that will deliver the correct flow at correct pressure. And it doesn’t wieght 100 lbs eihter. The supplier promised me I should have it this week, but we’ll see about that.

Popularity: 69% [?]

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Fully assembled membrane NF testing equipment

After fixing a couple of leaking connections and getting an electrician to connect the pump to the grid I’m finally ready to start filtering. So I will open the tube I got from Dow containing the NF270 and cut a suitable piece of the membrane and mount in the filter housing. More on that later.

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Assembling the membrane cell

Right now it’s a mess. I need to build a bench scale NF rig from the  Sterlitech CF042, a bunch of fittings and a huuuge pump (Hydracell M03). I’ve already connected the membrane cell so now remain to connect the wallplug and then the tubing from the pump to the membrane cell.

The diameter of the pump tubing is more than 22mm so I need to buy new tubing. Why this large diameter? I guess we’ll never know for sure…

Popularity: 78% [?]

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Leaking port and humic substances

Ok, the leaking injection valve is better, I simple picked it apart and cleaned it from some strange white precipitation, and put it back together, making sure to tighten those hex-nuts properly. So now it is only leaking when set to “Load”. Good thing. Maybe it is a missing septa that is the problem?

Also, the humic and fulvic acids that I’m going to study seem to be approximately in the range <1 kDa (meaning roughtly “less than 1000 carbon atoms per molecule”) . This means we’re way down there on the nanometer size range.

Also, the size and aggregation of the humic substances are greatly depending on the analytical conditions, such as pH, salinity and presence of other substances in solution (Shinozuka, 2003), meaning that when we analyze, we fundamentally alter the equilibrium state that existed in the undisturbed sample.

Below is a suggested molecular structure for humic acid (borrowed from here) .

Popularity: 83% [?]

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First injection of humics on HP-SEC

I injected 100 ul humic and fulvic acid containing sample (previously filtered through a 0.2 um syringe filter), with a flowrate of 0.5 ml min-1. Detected at 254 nm, the peaks looks terrible; poor separation and obviously too large sample volume. Oh well, change the sample loop, and try a different mobile phase, and/or lower the flowrate?

Still leaking though.

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News: Injection valve is leaking

Just found out that the septa is missing, and this could be why the injection valve is leaking. Well, what can you expect from old stuff that has been gathering dust for the last 10 years?

It is a special kind of challenge trying to conduct research on outdated instruments. You can still do good science, but the resistance is just a bit higher.

Now I will pick the injector valve apart and see if that can magically fix the problem.

Popularity: 85% [?]

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Building a see-through sandfilter

We got a comission to do some testing of a undisclosed filter material for an undisclosed company, and for that project I needed a see through sand filter. In the odd chance that anyone would be interested I’ll just throw the drawings up here.

I created this drawing quick and dirty in Word(!) and then let a workshop build it from clear polycarbonate plastic.

The outlet in the bottom is a so called mushroom nozzle(?), basically a plate with small channels cut out to minimize filter material escape. Missing on this drawing is a gasket which is needed to make the filter water tight.

Below is a picture of the finished filter housing, with a manometer and a cetrifugal pump which were used in the experiment. Flowrates in this setup were ranging between 1-5 litres per minute when the filter were filled with material. Back pressures were in the range 0.5-0.8 bar.

Do you need one of those? I can have them made for you, just contact me. Price per filter with approximate volume 10 liters is around $1,200, lower if several is ordered. Complete setup with pump etc. is available from $2,000.

Popularity: 85% [?]

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Setting up the old system

So I’m trying today to set up our old Waters system to run HP-SEC with an used TosoHaas TSK Gel 2000 column and our Fluorescence and UV detectors. The purpose is to characterize humic and fulvic acids in surface waters, and I envision later to connect the HP-SEC system to our ICP-MS. This would make HP-SEC-ICP-MS, a truly hyphenated system!

Anyway, I now need to make 0.025M ammonium acetate with 1% methanol mobile phase, then we’ll see if the old mule will cooperate.

Popularity: 85% [?]

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