I would like to take a bus from Jiujiang (Jiangxi) to Putuo shan, is this possible?

It is hard for you to finish this trip by bus, but if you really want to go, you may try other transportation method.
From Jiujiang, you can take a train to reach Hangzhou first and the train timetable can be searched on the Train Section on this website.
Upon reaching Hangzhou, you can find the direct buses to reach Shenjiamen Banshengdong where you can find the direct ferry to reach Putuoshan easily.