Which of the common and inexpensive hydrophobic reagents is used to convert the hydrophilic surface of silica into a hydrophobic surface?
To do this, I need a reagent that can be used on an industrial scale.
Which modifier is easy to work with, cheap and offers good quality?
Abolfazl Ahmadi
The resulting surface layer of fine particles of silica-containing raw materials is treated with a paraffin-containing aqueous emulsion. The hydrophobicity of a surface is characterized by the contact angle. A stable hydrophobic coating with a contact angle >120 is obtained, sufficient for the use of finely dispersed silica.
I do not know of industril processes doing whatyou are looking for. On a benche scale, that could be scaled-up I would suggest to was with a solution of a quaternary surface active agent, for example ditallow dimethyl ammonium chloride (DTDMAC). If you have an estimate of the surfcae charge of the silica you may esily calculate the stoichiolmetric amount of quat for a complete neutralisation. You will get apretty hydrophobic surface by then. Mind you, this may cause aggregation and you may go for a less drastic treatment by using for exampe less-than stoichiometric amount of DTDMAC or a more hydrophlic quat like benzalkonium chloride. Both DTMAC and benzalkonium chloride should be availble in industrial volumes.
Good luck
G. Bognolo
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