Adsorption of phosphate by Cu-loaded polyethylenimine modified wheat straw

Excessive phosphate can cause eutrophication of water bodies and disturb the balance of water organisms while the exhausted adsorbent can be further utilized to bind adsorbate for second adsorption. In this study, wheat straw (WS) was modified by grafting polyethylenimine (PEI) and PEI-WS was obtained, then Cu2+-loaded PEI-WS was used as adsorbent to bind phosphate (PO43–) from solution in batch mode and fixed-bed column mode (as secondary adsorption). PEI is successfully modified onto surface of WS through elemental analysis. The results of batch experiments showed that the adsorption capacity of Cu-PEI-WS for toward PO43– was 15.7 mg·g–1 (according to P) from experiments at 293 K. Adsorption isotherms were better fitted by Langmuir model and Temkin model while kinetic process was better fitted by Elovich model. The adsorption process was an exothermic spontaneous process. In column adsorption experiments, the effects of flow rate, column height and initial concentration of PO43– on break-through curves were investigated and Thomas model was suitable to fit results of column adsorption. Secondary adsorption of spent adsorbents is one way of reuse about some material and plays an important role in environmental protection.