Pretreatment of resin
Since there might be some impurities in the received XAD resins, cleaning was performed employing
the methodology as follows: Washed equal amounts of two resins by deionized water in filtration device.
Then mixed two kinds of resin and soaked them in d istilled methanol and acetone for more than 12h
respectively. At last, filtered the liquid and stored the resin in methanol to prevent the introduction of any
impurities until use.