Hello,
Through the process of vacuum filteration I am trying to obtain a thin film (few mm, e.g 1mm) of the precipitate on the filter paper (picture attached).
All of the literature I read gets flat precipitate layers however I am getting a dotted pattern where my precipitate accumulates and a lot more sample is needed to get a thin film (picture attached).
Therefore my question is how do I go about using vacuum filteration to get thin films of sample.
Do I need to filter a large amount of precipitate or do I need to alter my vacuum filteration set up?
Currently I am planning on increasing the number of filter paper in my Buchner funnel so any deformation is limited to the lower layers and I get a smooth layer on the uppermost filter paper.
Any advice would be greatly appreciated.
Thank you
Dear Joshua
I believe the easiest way to correct the morphology of you film is to use a filtering system with porous glass to sustain the filter paper:
https://www.amazon.com/QWORK-Filtration-Distillation-Apparatus-Filtering/dp/B0822LDSC3/ref=sr_1_9?dchild=1&keywords=laboratory+vacuum&qid=1620296533&sr=8-9
Those systems have a much more homogeneous suctions and result in more homogeneous films
Dear Joshua, as Remi said, you won't be able get a uniform film by the typical vacuum filteration through a Buchner funnel. I
For getting a high-quality film you should sieve your dispersion through a membrane filter using a sintered glass filteration set. Wide variety of membrane filters with different pore sizes (typically 0.2 & 0.45 micrometer) and made of different materials like Cellulose acetate, Nitrocellulose, PTFE, Nylone, and etc. are commercially available for different applications. Each of these membrane filters can provide a specific flow rate which is quite cruicial in fabricating a uniform film. Besides, before you buy one, you should consider the wetability of the membrane filter with the solvent that you use. For the polar solvents Nitrocellulose, cellulose acetate, nylone, polyethersulfone membranes are suitable but for non-polar hydrophobic solvents you should use PTFE membrane. Below you may find the pictures of such membranes together with the filteration set I told you about.
Best,
Dear Mr. Rémi Rafael and Mr. Mahdi Ghamsari,
Thank you so much for your response, I understand the issue I am facing.
Given that I already have a vacuum filtration set-up, however, the inappropriate funnel, would it be possible for me to purchase a sintered/fritted glass disc and place it within the Buchner funnel I currently have?
Or any other sort of alternatives I could apply to get a uniform suction under my filter paper.
Thank you
Although I think it wont work out that way, it is worth of trying. Besides, its so unlikely to get a uniform stable film using typical filter paper due to its large pores and high filteration rate. So, you should look for a membrane filter so you can get exactly what you want.
Good luck,
Wang, Zhiguo, Wenwen Zhang, Juan Yu, Lijun Zhang, Liang Liu, Xiaofan Zhou, Chaobo Huang, and Yimin Fan. "Preparation of nanocellulose/filter paper (NC/FP) composite membranes for high-performance filtration." Cellulose 26, no. 2 (2019): 1183-1194.
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