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 distilled 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.