Synthesis, characterization and evaluation of amphoteric chitosan‐based grafting flocculants for removing contaminants with opposite surface charges from oilfield wastewater

Abstract

AbstractBACKGROUNDContaminants with either negative or positive surface charges in wastewater generated from oilfields are normally very difficult to remove by traditional flocculants owing to their strong pH‐dependence and high health risks. Natural polymer flocculants, especially chitosan‐based flocculants, have attracted much interest for their environmental friendliness, excellent flocculation efficiencies and cost‐effectiveness.RESULTSA series of amphoteric chitosan‐based grafting flocculants (CM‐chi)‐g‐PDMDAAC (denoted as CgPD) were successfully synthesized by grafting diallyl dimethyl ammonium chloride (DMDAAC) onto carboxymethyl chitosan (CM‐chi) with different grafting ratios. By carboxymethyl and grafting modification, dramatically increased water solubility of chitosan was obtained. The physicochemical structure of CgPD products was characterized by 1H NMR and elemental analysis proving that DMDAACC was grafted onto CM‐chi appropriately. Flocculation effects of CgPD were studied in kaolin and hematite suspensions having opposite surface charges. These CgPD flocculants demonstrated an excellent performance in respect of flocculation window, optimal dosage and pH sensitivity. In addition, CgPD was proven to be applicable as a flocculant in water treatment of oilfield sites.CONCLUSIONThe biodegradability flocculants, CgPD, can effectively remove contaminants with opposite surface charges from oilfield wastewater with low optimal dosage, wide flocculation window, low pH sensitivity and less environmental impacts than traditional flocculants. © 2017 Society of Chemical Industry