Efflorescence is a residue left over from a bonding agent in the cement as the moisture passes through it. If your wondering if it’s harmful please don’t . However is does mean the original waterproofing has worn off and that your basement has a moisture issue.
Can it be removed YES efflorescence can be removed. Power wash and a some scrubbing with a chemical cleaner will take care of your issue. Several applications are better than one. However cleaning efflorescence from your walls does not cure the problem, it only removes the symptoms. To cure you issue you must find where the moisture/water is entering the wall and correct it.