What is the ruling on my job collecting and depositing money in a non-Islamic bank, and is it permissible to give a portion of my salary as charity to purify it?

It is not permissible to deposit checks in an interest-based bank, as it constitutes assisting in sin, unless the deposit is into a current account due to necessity, in which case it is permissible. As for the effect of this matter on the salary, if it is not part of the required work, then it has no effect. But if it is part of it, then the salary is unlawful to the extent of this work, and one must dispose of this amount by spending it on the welfare of Muslims.