| During operation,industrial circulating cooling water systems often encounter scaling problems due to evaporation of moisture,and the like.The use of scale inhibitors is a simple,economical and efficient method of inhibiting scaling.However,the phosphorus-containing scale inhibitors commonly used in the industry will lead to eutrophication of water bodies;the carboxylic acid scale inhibitors are not easily biodegraded,which will bring harm to the environment and violate the concept of sustainable development.Therefore,a green,economical and phosphorus-free pentaerythritol-?-cyclodextrin tetrapod(PT-?-CD)was prepared and its scale inhibition performance and mechanism were studied and analyzed.It is expected to expand the application of ?-cyclodextrin in circulating water systems.Firstly,in this paper,the pentaerythritol and ?-cyclodextrin were used as raw materials to synthesize green pentaerythritol-?-cyclodextrin tetrapod(PT-?-CD)by a successive one-pot process.The structure of PT-?-CD was confirmed by the FT-IR and 1H NMR,which demonstrated that PT-?-CD was successfully synthesized.Next,the scale inhibition performance of PT-?-CD was measured by calcium carbonate deposition method,and the morphology and crystal form of calcium carbonate particles were characterized by means of SEM,XRD and TG.Besides,the mechanism of action of PT-?-CD was analyzed based on the experimental results.Finally,baesd on the research of this laboratory,two other laboratory-made linear derivatives of ?-cyclodextrin(?-CD-PEG400 and ?-CD-L61)were selected.By comparing their scale inhibition properties,the relationship between their molecular structure and scale inhibition performance was discussed,which provided a reference for subsequent research.The research of this thesis has the following conclusions:(1)The scale inhibition efficiency gradually increases with the increase of concentration of PT-?-CD.The optimum scale inhibitor dosage is 140 mg/L,and the corresponding scale inhibition rate is 89.45%,indicating that the tetrapod compound has a certain ability of scale inhibition.However,the bath time,temperature and Ca2+ concentration all have an effect on the scale inhibition rate.The scale inhibition rate shows a decreasing trend as they increase;(2)The SEM,XRD and TG images of calcium carbonate scale samples before and after adding PT-?-CD were compared and analyzed.The results of the analysis and calcium carbonate deposition experiments show the inhibition mechanism of PT-?-CD.The PT-?-CD molecular structure with-OH,C-O-C and cavity can inhibit the formation and growth of CaCO3 crystals and change the morphology of CaCO3 by chelation,dispersion and lattice distortion.(3)By comparing the scale inhibition rates of the tetrapod structure(PT-?-CD)and the linear structure(?-CD-PEG400 and ?-CD-L61)?-CD derivatives,it can be clearly seen that their scale inhibition rates increase with the increase of the addition amount.The optimum scale inhibitors for PT-?-CD and ?-CD-PEG400 are 140 mg/L and 180 mg/L respectively,and the corresponding scale inhibition rates are 89.45%,76.48%.The scale inhibition effect is ranked as PT-?-CD>?-CD-PEG400>?-CD-L61,reflecting that different molecular structures will affect the scale inhibition rate.The hydrophilic chain is more advantageous than the hydrophobic chain in inhibiting the formation of scale.The tetrapod structure of PT-?-CD prepared in this paper is more favorable for scale inhibition than the linear structure of(3-CD-PEG400.(4)The scale inhibition rates of the three p-CD derivatives decrease with bath time,temperature and Ca2+concentration.But the degree of impact is different under different conditions.Among them,PT-?-CD has better timeliness than ?-CD-PEG400 and(3-CD-L61.?-CD-PEG400 and PT-?-CD can work better at temperatures below 90? and 80?,respectively.PT-?-CD is more suitable for treating industrial circulating cooling water with high Ca2+ concentration,but its tolerance to calcium needs to be further improved.From the results,it can be inferred that tetrapod structure of PT-P-CD has better dispersion stability than the linear structures of p-CD-PEG400 and ?-CD-L61.(5)Through the analysis of the morphology of scales,it can be visually seen that the appearance of the scale samples has changed after the addition of ?-CD-PEG400 and PT-P-CD.The scale sample after addition of ?-CD-L61 is basically rhomboid.The comparison results of SEM image are consistent with the conclusion of calcium carbonate deposition experiments that PT-?-CD has stronger scale inhibition ability among the three?-CD derivatives.Starting from the structure of the three derivatives,the reason for this difference may be the four-legged structure of PT-?-CD.The four molecular chains cooperate with each other to make the dispersing ability stronger than the single EO molecular chain of?-CD-PEG400,and ?-CD-L61 has a lower scale inhibition rate due to the influence of its PO hydrophobic chain. |
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