Identification of components in composite coagulant AS/PDMDAAC by ATR-FTIR

The water treatment efficacy of composite coagulants is closely related to their chemical composition. Aluminum sulfate/poly dimethyl diallyl ammonium chloride (AS/PDMDAAC), a novel and efficient composite coagulant, faces challenges in its promotion and application due to the lack of effective qualitative analysis methods. In this study, a method based on Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was proposed. First, different sample preparation methods were compared, and the hot plate drying method was selected as the most efficient preparation technique. By combining the FTIR spectra of individual component, standard FTIR spectra for three different mass ratios of AS/PDMDAAC were established, and the origins of various characteristic peaks in the composite were explained in detail. To further validate the sample composition, three types of spiking recovery experiments were designed. Finally, based on the experimental results, a component identification workflow was summarized, enabling successful qualitative analysis of the samples as either AS/PDMDAAC, non-AS/PDMDAAC, or AS/PDMDAAC containing an impurity.