The Influence Of Chitosan And Its Derivatives On The Stability Of Silicic Acid Solution

In the marine ecosystem,there is the problem of dealing with excess silicon every year.Silicon is usually present in the form of soluble silicic acid,and then the amorphous hydrated silica is produced by the process of biosilicidation.As a major contributor to silicon in the ocean,diatoms can maintain a higher level of silicic acid in the"silicon pool"solution,this is primarily due to the existence of biological macromolecules in diatoms.Therefore,it has great significance and practical application value to study the stability of biological macromolecules chitosan and its derivatives to silicic acid.As a biodegradable macromolecule,chitosan can be modified by chemical modification to obtain chitosan derivatives due to the distribution of many functional groups such as hydroxyl and amino groups on the macromolecular chains.It has a wide range of applications.In this paper,the effects of several kinds of chitosan derivatives on the stability of silicic acid have been studied,and the influence of chitosan and its derivatives on the stability of silicic acid in neutral supersaturated aqueous solution was studied by silicon molybdenum blue spectrophotometry,the structure of amorphous sediments were characterized by means of SEM and ²⁹Si NMR.The specific contents are as follows:?1?Through the investigation and improvement of the dosages of various reagents and the absorbance of soluble silicon in the visible spectrophotometry of silicon molybdenum blue,a set of test methods suitable for the determination of soluble silicon in the effective range of the experiment finally are summarized.1 mL dilute hydrochloric acid and 2 mL ammonium molybdate were added to 50 mL silicon solution,1.5 mL oxalic acid was added 10 minutes later,1.5 mL ascorbic acid was added within two minutes,and the wavelength was 590 nm.The relation between the silicon content and the absorbance is Y=2.7×10^-33 Z+0.11,where Z represents the soluble silicon content in the solution,calculated as ppm.?2?The effects of three different types of chitosan?water-soluble chitosan,chitosan quaternary ammonium salt,and carboxylated chitosan?on the stability of silicic acid in neutral supersaturated aqueous solutions were investigated.The results show that the chitosan quaternary ammonium salt has a certain inhibitory effect on the polycondensation of silicic acid compared to the other two chitosan derivatives,and its optimum concentration is 20 ppm.In the high concentration of silicic acid solution,the addition of chitosan quaternary ammonium salt can not only change the aggregation state of polysilicic acid,but also reduce the degree of polymerization of polysilicic acid,indicating that it can inhibit the polycondensation of silicic acid.?3?Another zwitterionic polymer phosphorylated chitosan?PCH?was obtained by further modification of chitosan,and the importance of synergies between polyelectrolytes on silica inhibition is also discussed.The main research results of this chapter are summarized as follows:PCH is an effective inhibitor of silicic acid condensation.It can maintain a certain concentration of soluble silicic acid in the dosage range of 40²00 ppm.PCH cannot completely inhibit the polymerization of silicic acid?initial concentration is 500 ppm?,and the experiment shows that it can only delay the polycondensation reaction of silicate acid within a certain time range.Furthermore,the effects of either purely cationic?polyethyleneimine,PEI?or purely anionic?carboxymethyl inulin?polyelectrolytes on the inhibitory activity of PCH are systematically studied.It was found that the action of inhibitor blends is not cumulative.PCH/PEI blends stabilize the same level of silicic acid as PCH alone in both short-term?8 h?and long-term?72 h?experiments.However,the compound of anionic CMI and PCH can effectively delay the Polycondensation of silicic acid in a short time.