Preparation And Application Of Sugar Clarifier For Arginine Modified Magnetic Chitosan

The sulfitation processes with SO₂as the main clarifier is widely used for clarification and decolorization in sugar mills at home and abroad.The method has the advantages of short process,simple process and low production cost.However,there are some problems,such as:the white sugar produced by this method has the problems of high residual sulfur content,changeable yellow,moisture absorption,and low quality grade.Additionally,the method has low clarification efficiency.To overcome the above problems,arginine modified magnetic chitosan（AMCS）,a new clarifier,was prepared from chitosan,and its application in sugarcane juice clarification was studied.The details are as follows:Firstly,chitosan（CS）,arginine（Arg）and Fe₃O₄were used as raw materials and sodium tripolyphosphate（TPP）as cross-linking agent.AMCS was prepared by ionic cross-linking technique and graft modification.The preparation conditions of AMCS were optimized by single factor and orthogonal design.The optimum conditions wereas follows:the p H of the prepared magnetic chitosan was 4.5,the CS addition amount was 1.0 g,the Arg addition amount was 0.72 g,the TPP concentration was 1.5%,the grafting time was 10.0 h,and a fixed molar ratio of NHS/EDC/arginine of 1:2:3.The AMCS prepared under thses conditions was used for clarification of mixed juice,and the gravity purity difference and decolorization ratio of the clear juice were 2.93%and 69.93%,respectively.In addition,AMCS was characterized by a series of characterizations such as scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,and vibrating sample magnetometer（VSM）and so on.It was found that AMCS has a three-dimensional network structure,with a specific surface area 12.23 times that of CS.The crystal structure of Fe₃O₄in AMCS was not affected after modification.In addition,AMCS has good magnetic separation performance and adsorption performance.Secondly,AMCS was used for the clarification of mixed juice.The clarification process conditions of AMCS was optimized by single factor and response surface,namely,the total effective P₂O₅was 390 ppm,the p H value of the secondary lime juice was 6.92,the amount of PAM was 1.82 ppm,the amount of AMCS was 1.01 g/L and the adsorption temperature was 55.50°C.Under these conditions,the gravity purity difference,decolorization ratio and the turbidity of the clear juice are 3.14%,72.01%and 34.82 MAU,respectively.The comparison between AMCS clarification and sulfitation processes shows that AMCS is feasible as a clarifier in the purification of mixed juice.Then,the adsorption mechanism of gallic acid（GA）by AMCS was studied.The results show that the AMCS adsorption process for GA is a single layer adsorption and spontaneous endothermic process.The adsorption mechanism is mainly electrostatic attraction,which may be accompanied by micropore filling.The presence of Ca²⁺and K⁺（concentration of K⁺>16 mmol/L）in sugar solution promoted the adsorption of GA on AMCS,while Na⁺had almost no effect.Finally,the regeneration performance of AMCS was studied.The regeneration condition was 95%CH₃CH₂OH for 6.0 h.Under the condition of repeated regeneration,AMCS after five times of regeneration was used for the clarification of mixed juice,the gravity purity difference and decolorization ratio of its clear juice were 2.00%and 71.61%,respectively.Therefore,AMCS is a promising clarifier which can be reused.