| pH-sensitive smart materials are a class of materials that convert external pH stimuli into signals that we can directly discern.They can be used to facilitate pH measurement while ensuring accurate results.It has great application prospects in many fields such as medicine and pharmacy.A pH-induced color-sensitive membrane is a common pH-sensitive smart material.Indicators are the key to pH sensitive material sensitive membranes,while traditional adsorption and embedding methods in pH preparation tend to cause dye leakage.Shrimp shell powder has more active groups and is a potential indicator fixing material,but its adsorption performance on dyes still lacks sufficient experimental basis.In this study,shrimp shell powder adsorption was used as a dye immobilization method to prepare pH-induced color-sensitive membranes and a pH measurement method based on colorimetric method was developed.The preparation and application of this pH-sensitive smart material was preliminarily explored,meanwhile,a new way of high-valued utilization of wasted shrimp shells was also providedShrimp shell-based bio-adsorbent was prepared and used to treat the simulated wastewater with congo red or methylene blue,exploring the possibility of adsorption of shrimp shell powder as a means of dye immobilization.The effects of temperature,adsorption time,initial dye concentration,adsorbent dosage and initial solution pH on adsorption efficiency were investigated,the prediction model for removal efficiency was subsequently built,and the adsorption isotherm,adsorption kinetics and adsorption thermodynamics were systematically studied.The results showed that the adsorption of congo red and methylene blue by shrimp shell powder reached equilibrium at 24 h and 4 h,respectively.The equilibrium adsorption capacity increased with increasing adsorption time,the initial dye concentration and adsorbent dosage.As pH increased,the equilibrium adsorption capacity of congo red increased,while the equilibrium adsorption capacity of methylene blue almost presented no change with pH.At 15 ?,absorbent dose of 1 g·L-1,the optimum contact time of 24 h and pH=4,the saturated adsorption capacity of congo red by shrimp shell powder was 276.64 mg g-1,while that of methylene blue was 1.44 mg·g-1 at pH=12.The adsorption of congo red and methylene blue onto shrimp shell was mainly considered as a physical adsorption process and could be described by a quasi-second-order model.Overall,shrimp shell-based bio-adsorbent exhibited an excellent removal efficiency for cation dye,while a slight removal one for anion dye.It can be used as an anionic dye adsorption fixative.Shrimp shell powder,N,N-dimethylformamide,acetone,dichloromethane and polyethylene glycol were used as additives to prepare cellulose acetate-based pH-sensitive membranes,which were subsequently characterized.The effects of activation methods,solution pH and shrimp shell powder dosage on the film formation were studied.The response performance and stability of pH-sensitive membranes at different pH solutions were studied.A data-filtering process model based on colorimetry was constructed and the mathematics relationship of pH and hue was preliminarily established.The study found that shrimp shell adsorbent could effectively fix congo red,and acid dissolution of calcium in it led to change of the internal and external structure of the membrane.Hence,shrimp shell powder functioned as adsorbent and porogen in the preparation of the membrane.Dichloromethane allowed the pH-sensitive membrane to have more channels and a rougher surface.Polyethylene glycol was mainly used as a dispersing agent,which introduced a large amount of hydroxyl groups and enhanced the hydrophilicity of the membrane.Both the acid-activation and the alkali-activation could enhance the mass transfer ability of the membrane.The response time of the sensitive membranes was less than 10 s and the stability of pH response was hardly affected by solution pH.The membrane structure was relatively stable.The amount of dye leakage was small,and 0.05 g of shrimp shell powder adsorbent was sufficient for consolidating congo red.In the matlab operating environment,the color model transformation of the film image did not affect the value of the image pixel.The bilateral filtering data had better fitting effect than the unfiltered data because of the function of both spatial and range filtering.The linear response of pH measured by the prepared pH-sensitive membrane ranges from 3.20 to 5.23.Sensitive membranes based on congo red adsorption have great potential in pH measurement.The pH-sensitive membrane based on congo red adsorption has stable structure and good sensing performance.It is both a kind of intelligent material with great application value in the field of pH measurement and a new idea for the recycling and higher-value application of shrimp shell powder. |
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