A study on fluorescence properties of carboxymethyl-quaternary ammonium oligochitosan and its performances as a tracing agent

Carboxymethyl-quaternary ammonium oligochitosan (CM-QAOC) exhibited high inhibition to scaling and microbial formation and also remarkable fluorescence. In this paper its fluorescent properties and application as a fluorescent tracing chemical for industrial water treatment were studied in detail. The fluorescence intensities of CM-QAOC were in good linear agreement with its content in the concentration range of 5 to 500 mg/L and in the range of pH 7 to 9, which shows CM-QAOC can trace itself directly. The results showed the fluorescence would not be influenced by common phosphorus-containing organic and inorganic water treatment chemicals and N-dodecyl-N,N-dimethyl-benzenemethanaminium chloride. This means CM-QAOC is compatible with those chemicals. The metal ions Ca²⁺, Mg²⁺, Fe³⁺ and Cu²⁺ from raw water or corrosion products could cause obvious enhancement in fluorescence intensities and sometimes blue-shifts in the fluorescence maxima, which demonstrated CM-QAOC could also be used as tracer to monitor damages like corrosion and scaling in water systems, by varying changes of fluorescence intensities and maximum emission wavelength. The fluorescence of CM-QAOC may be influenced by NaClO, and be quenched by sunshine slightly. Its ratio of biochemical oxygen demand to chemical oxygen demand was 0.53, which indicates CM-QAOC is a biodegradable chemical. Therefore, CM-QAOC can be applied as a tracer and environmental-friendly chemical for industrial cooling water treatment.