Preparation Of Polycaprolactone Porous Monolithic Materials And Its Application In Dye Treatment

In recent years,the development of the textile industry and the printing industry have made the problem of dye pollution more and more serious.Dye wastewater treatment has attracted great attention.At present,there are a variety of dye treatment technologies,most of which use the photocatalytic effect of semiconductor materials?such as titanium dioxide?or a variety of chemical and physical effects to degrade them.However,these methods require complicated processes and low processing efficiency.This paper discusses the preparation of a simple and efficient gold-containing catalyst carrier and its dye processing performance using the non-solvent thermally induced phase separation?NTIPS?method.In this paper,polycaprolactone?PCL?was selected as the matrix material,dioxane as the good solvent,and water or ethanol as the non-solvents.The solubility parameters between PCL and different solvents and the effect of different non-solvents on the NTIPS process are discussed.The first part discussed the effect of different types of non-solvents on the NTIPS process when polycaprolactone?PCL?was used as the matrix material.It was found that when 20?,4?,and-18?were chosen as phase separation quenching temperatures,PCL monolith can be obtained by phase separation in PCL-E30/70?dioxane/ethanol v/v 30/70?.While PCL monolith only can be obtained at-18?in PCL-W90/10?dioxane/water v/v 90/10?.Through the calculation of solubility parameters and solubility space,the dioxane-water system can be regarded as a good solvent for PCL at the three phase separation quenching temperatures of the experiment,so spontaneous phase separation was more difficult.When the temperature belowed the freezing point of the solvent at-18?,phase separation occured due to the crystallization of the solvent.For the dioxane-ethanol system,it was non-solvent of PCL under the experimental temperature,so phase separation can occur spontaneously.Based on the analysis of theoretical and experimental results,when ethanol was used as a non-solvent,the proportion of dioxane in the mixed solvent can be reduced,making the preparation process of monolith more environmentally friendly.The phase separation process was simplified,the process window was expanded and energy consumption was reduced.Furthermore,the cloud point was determined to draw the ternary phase diagram,which can be used to predict the process parameter range of PCL monolith prepared by the NTIPS method.Subsequently,this article discussed in detail the effects of different mixed solvent ratio,phase separation temperature,polymer concentration and other parameters on the structure and performance of PCL monolith.SEM results and nitrogen adsorption-desorption experiments showed that the PCL monolith prepared in this paper has a multi-level pore structure,which was composed of three levels of geometric features.The first level was the accumulation of PCL"golf ball"structures or sponge-like continuous porous structures.The second level was the lotus leaf surface of spherical particles/skeletons or nanofiber structures.The third level was the nanopores shown in the BET results.The pore structure of the first two levels seemed to be highly dependent on the phase separation temperature.When the phase separation temperature was high,the phase separation speed was slow.The liquid-liquid?L-L?phase separation follows the nucleation-growth mechanism,resulting in a"golf ball"-like structure.When the phase separation temperature was low,the L-L phase separation followed the spinodal decomposition mechanism,resulting in a"sponge-like"structure.Non-solvent ratio also had an effect on the structure of monolith.As it increased,the diameter of the monolithic"golf ball"structure also increased,and the round hole structure on the spherical surface increased.The effect of polymer concentration on PCL monolith was small,and as the polymer concentration increased,the diameter of the"golf like"structure of monolith decreased.Monolith under different conditions had a higher specific surface area,which would contribute to the application of catalyst carrier to increase the reaction contact area.Finally,a one-step modification method was used to prepare a super-hydrophilic polydopamine-modified PDA-PCL monolith,and Au nanoparticles were successfully immobilized on the surface of PDA-PCL monolith to obtain Au@PDA-PCL monolith.The azo dye methyl orange was selected as the model dye for catalytic experiments.By changing the initial concentration of methyl orange and the concentration of reducing agent Na BH₄,the decomposition efficiency of methyl orange under different conditions was verified.It was proved that Au@PDA-PCL monolith had higher catalytic efficiency at higher dye concentration and Na BH₄concentration.When the initial concentration of methyl orange was 75 mg/L and the concentration of Na BH₄was 0.05 mol/L,the catalytic efficiency was the highest,the decomposition rate of methyl orange was as high as 80%within 5 minutes.At the same time,the gold-containing catalyst carrier Au@PDA-PCL monolith was tested for recycling performance.It was found that after repeated operations 4 times,the catalytic efficiency of Au@PDA-PCL monolith hardly changed,proving that the material has good recycling performance.In summary,this paper useed a simple NTIPS method to prepare a PCL monolith with a multi-stage pore structure with adjustable morphology,and a one-step modification was used by dopamine self-polymerization to prepare a porous support material PDA-PCL with a super-hydrophilic surface.It is used to decompose methyl orange by immobilized Au nanoparticles,showing good catalytic efficiency.This provides a certain theoretical guidance and experimental basis for the preparation of efficient catalyst supports and their treatment of dye pollution,especially azo dye pollution.