Nitrate Uptake by Cellulose-Based Anion Exchange Polymers Derived from Wheat Straw

Nitrate contamination of ground water is a serious problem due to the intensive agricultural activities needed to feed the world’s growing population. While effective, drinking water treatment using commercial ion exchange polymers is often too expensive to be employed. At the same time, lignocellulosic waste from crop production—an abundant source of the renewable polymer cellulose—is often burned to clear fields. This results in not only adverse health outcomes, but also wastes a valuable resource. In this study, wheat straw was pretreated to extract cellulose, then selectively oxidized with periodate, crosslinked with an alkyl diamine (1,7-diaminoheptane or 1,10-diaminodecane), and functionalized with a quaternary ammonium compound ((2-aminoethyl)trimethyl ammonium chloride) to generate a cellulose-based anion exchange polymer. This polymer lowered aqueous nitrate concentrations to health-based drinking water standards. Unlike commercial ion exchange polymers, its synthesis did not require the use of toxic epichlorohydrin or flammable solvents. The pretreatment conditions did not significantly affect nitrate uptake, but the crosslinker chain length did, with polymers crosslinked with 1,10-diaminodecane showing no nitrate uptake. Agricultural-waste-based anion exchange polymers could accelerate progress toward the sustainable development goals by providing low-cost materials for nitrate removal from water.