Preparation And Characterization Of Xanthan-Metal Salt Composite Flocculant And Its Application In Red Tide Mitigation

In this thesis,microbial flocculant xanthan gum mixed with metal salt FeCl₃ and AlCl₃,respectively,to form new composite flocculants.The prepared xanthan-FeCl₃and xanthan-AlCl₃ were characterized using multiple techniques.Their flocculation effects on Prorocentrum donghaiense and Heterosigma akashiwo were explored,and the mechanism was also discussed.The main research contents are as follows:1.The prepared xanthan-FeCl₃ and xanthan-AlCl₃ at different ratio were characterized using X-ray diffraction,infrared spectrum and Zeta potential techniques.The results indicated that the structure and Zeta potential of xanthan-metal salt have changed,which was helpful to enhance its flocculation ability.2.The results of flocculation tests showed that algal removal efficiencies of xanthan-metal salt are significantly enhanced comparing with xanthan or metal salt.when the composite dosage was 20 mg/L xanthan and 60 mg/L metal salt,the removal efficiency of Prorocentrum donghaiense and Heterosigma akashiwo were over 95%,which was increased by 45.6%⁵3.9%comparing with 20 mg/L xanthan or60 mg/L metal salt used alone.3.Algal particle sizes on-line monitoring suggested that xanthan-metal salt flocculants are beneficial to the formation and growth of algae flocs.Moreover,the algal floc size is larger and denser.The Algae floc size d₅₀ of xanthan-metal salt was1227?m,which was significantly larger than that of xanthan?150?m?and metal salt?874?m?used alone.4.The results of zeta potential monitoring and microscopic imagines suggested that the algal flocculation mechanism of xanthan-metal salt is mainly charge neutralization,adsorption bridge and net trapping and so on.