Mercury is still one of the heavy metals that takes a long time to detoxify with the remedies we know today - that is, if we want to do it safely and not risk redistributing it around our body and brain.
Redistribution is a major concern with some of the methods widely used today i.e. DMPS and DMSA along with taking chlorella alone (must always be taken with another thiol-containing substance such as cilantro, as it is not stable for detox purposes taken alone). Important to be aware that approx. 30% of people can't tolerate chlorella very well, which might be due to optimized function of the enzyme cellulase. If you are unable to tolerate chlorella, one might consider adding an enzyme with cellulase in it to help digest the chlorella.
Recently more and more studies with chitosan, however, seem to show that this substance may be more effective for mercury.
Read some of the studies here:
Article in Journal of Molecular Liquids 214:175-191 · February 2016