The Adsorption Effects And Mechanisms Of Methylene Blue And Malachite Green In Water By The Chinese Medicine Decoction Residues Of Paeoniae Radix Alba,Tetrapanacis Medulla,Prunellae Spica

Research background and purpose:Today,it is estimated that the annual emission of Chinese medicine residues in China exceeds 60 million tons,and many scholars at home and abroad have explored the comprehensive way of utilizing Chinese medicine residues in order to improve their reuse value.According to references,it has been found that the annual emission of wastewater from the textile industry in China is up to 2 billion tons,posing a serious threat to the ecological health of the water environment.The biosorption method has been focused on by domestic and foreign scholars for its advantages of environmental friendliness,easy operation,inexpensive materials and high adsorption capacity.Among the biosorbent material sources,Chinese medicine residues,which have the advantages of high biosorbent void space,large specific surface area and rich in various functional groups,have been prepared by some scholars as biosorbents and used for the removal of target pollutants in water.Therefore,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were prepared as biosorbents for the removal of MB and MG from water in this thesis,and the removal processes and mechanisms were investigated to provide a simple and efficient method for the removal of MB and MG from aqueous solutions,it also provides an effective treatment way for the reuse of Chinese medicine residues and realizes the social benefits of"treating pollution with waste".Materials and Methods:Materials:Chinese herbal medicines（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were purchased in Chengdu Wuquashi Chinese herbal wholesale market were decocted in accordance with the"Code of Practice for the Management of Chinese Medicine Decoction Rooms in Medical Institutions",after which they were washed,crushed and sieved to make biosorbents of different particle sizes of Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）.Methods:Firstly,the effects of five factors on the removals of methylene blue（MB）and malachite green（MG）from the aqueous solution of Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were investigated by single-factor adsorption experiments,including solution p H,adsorbent dosage,adsorption time,initial concentration of solution,adsorbent particle size.Secondly,the Box-Behnken Design（BBD）experiment in Response surface method（RSM）was used to investigate the intensity of the four investigated factors（solution p H,adsorbent dosage,adsorption time,and initial concentration of solution）affecting the MB and MG removals from aqueous solution by the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）,and their interaction effects on the removals of MB and MG,and the optimal combination of adsorption conditions between the investigated factors and their application conditions.After that,the adsorption processes of MB and MG by Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were investigated by material characterization,isothermal models and adsorption kinetic models to deduce their adsorption mechanisms.Finally,the anions and cations of the solutions before and after the adsorption of MB and MG by Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were detected by atomic absorption method（AAS）and ion chromatography（IC）.The pollution risk was assessed by single pollution index and comprehensive pollution index methods.Results:1.The single-factor adsorption experiments showed that,at the solution p H of 10.0,the decoction residues of Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）reached the maximum removal rates of51.02%,47.93%,76.99%（MB）and 45.31%,78.13%,73.44%（MG）,respectively.At the adsorbent dosage of 5 g·L^-1,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）reached the maximum removal rates of84.54%,84.54%,91.38%（MB）and 73.31%,90.49%,87.06%（MG）,respectively.When the adsorption time was 360 min,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）reached the maximum removal rates of 65.84%,76.51%,88.97%（MB）and 43.90%,68.29%,73.17%（MG）,respectively.When the initial concentration of the solution was 100 mg·L^-1,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）reached the maximum removal rates of 60.14%,75.60%,89.35%（MB）and 43.27%,76.92%,73.39%（MG）,respectively.When the particle size was 0.18,0.25 and 0.355 mm,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）reached the maximum removal rate of 32.16%,81.16%,82.70%（MB）and 34.87%,56.87%,69.52%（MG）,respectively.2.The response surface optimization experiments showed that,the effects of adsorbent dosage（A）,solution initial concentration（B）,solution p H（C）and adsorption time（D）on the adsorption MB removal rates of Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）from large to small were as follows:D>A>C>B,C>A>B>D and C>D>A>B,respectively;the effects on MG removal rates from large to small were as follows:C>D>A>B,C>A>B>D and C>A>D>B.When the adsorbent dosage was 5 g·L^-1,the initial concentration of the solution was 400mg·L^-1,the p H of the solution was 6.0,and the adsorption time was 229 min,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）showed the maximum removal rates of MB and MG,and the predicted values of the maximum removal rates of MB were 88.54%,73.71%,93.47%,and the predicted values for the maximum removals of MG were 84.95%,92.39%,97.09%.Then,the validation experiments revealed that the actual and predicted values of MB removal by the Chinese decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were 98.35%,95.89%and 93.85%,respectively,and the values of MG removal were 93.71%,96.02%and 96.20%,respectively,and the actual values were in good agreement with the predicted values.3.The adsorption isothermal models fitting showed that,the adsorption processes of the decoction residue of Paeoniae Radix Alba on MB,and the decoction residue of Tetrapanacis Medulla on MB and MG were consistent with Langmuir,and the maximum adsorption amounts were 107.99 mg·g^-1,112.87 mg·g^-1 and 164.26 mg·g^-1,respectively.The adsorption processes of the decoction residue of Paeoniae Radix Alba on MG,and the decoction residue of Prunellae Spica on MB and MG were in accordance with Freundlich,and the maximum adsorption amounts were 164.74 mg·g^-1,238.84 mg·g^-1and 300.42 mg·g^-1,respectively.The adsorption of MB and MG by the decoction residue of Prunellae Spica was greater than the decoction residues of Tetrapanacis Medulla and Paeoniae Radix Alba.In addition,the kinetic adsorption processes of MB and MG by Chinese decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were in line with the pseudo-second-order kinetic model.The results of characterization showed that,the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）after the adsorption of MB and MG,some elements appeared to be increased and decreased（Paeoniae Radix Alba decoction residue appeared Na and Mg elements and disappeared S element,the content of C element was increased.Tetrapanacis Medulla decoction residue appeared Na element;Prunellae Spica decoction residue appeared Na,N and O elements,the content of C element decreases and S element disappears）,as well as the specific surface area increased,the pore volume deepened,the average pore size decreased,and the zeta potential changed（The zeta potential of the decoction residue of Paeoniae Radix Alba changed from-30.7 mv to-15.9 mv（MB）and-4.55 mv（MG）;the zeta potential of the decoction residue of Tetrapanacis Medulla changed from-12.8 mv to-7.58 mv（MB）and-8.3 mv（MG）;the zeta potential of the decoction residue of Prunellae Spica changed from-18.4 mv to-5.42 mv（MB）and-3.55 mv（MG））.In addition,the decoction residues of Tetrapanacis Medulla and Prunellae Spica after adsorption of MB and MG also showed changes in IR functional groups（the-C=O,-COO and-C-O groups of the decoction residue of Tetrapanacis Medulla are displaced;the-COO,-C-O,-COO and-COOH groups of the decoction residue of Prunellae Spica are displaced,intensified or weakened）.4.The anion assay and risk assessment showed that,the solution of MB exists with Na⁺,Cl^-and SO₄^2-,and the solution of MG exists with Na⁺,Ca²⁺,Mg²⁺,Cl^-and SO₄^2-.After the decoction residues of Paeoniae Radix Alba and Prunellae Spica adsorbed MB,the solution contained K⁺,Na⁺,Ca²⁺,Mg²⁺,Cl^-and SO₄^2-.After the decoction residue of Tetrapanacis Medulla adsorbed MB,the solution exists with K⁺,Na⁺,Ca²⁺,Cl^-and SO₄^2-.After the adsorption of MG on the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）,the solutions exist with K⁺,Na⁺,Ca²⁺,Mg²⁺,Cl^-and SO₄^2-.The assessment results of the single-factor pollution index method showed that the contents of Na⁺,Cl^-,and SO₄^2-in the solutions of MB and MG solutions,as well as the solutions of Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）after adsorption of MB and MG did not exceed GB 5749-2006 and GB 3838-2002 in the secondary standard limit value.The assessment results of the integrated pollution index method showed that the water quality condition of MB solution was mildly polluted and the water quality condition of MG solution was good.After the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）adsorbed MB and MG,the water quality of the solution was in a better condition and did not cause pollution.Conclusions:1.The Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）have good potential adsorption for MB and MG in water.2.The response surface models for the adsorption of MB and MG in water by Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）was successfully established.The degrees of influence and interaction of the investigated factors on the removal of MB and MG were clarified,and the optimal combinations of parameters for the adsorption of MB and MG in water by the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were obtained by RSM,respectively.3.The adsorption processes of MB by decoction residue of Paeoniae Radix Alba,MB and MG by decoction residue of Tetrapanacis Medulla are uniform adsorption on single molecular layer;furthermore,the adsorption processes of MG by decoction residue of Paeoniae Radix Alba,MB and MG by decoction residue of Prunellae Spica are multilayer adsorption on non-uniform surface.The kinetic adsorption processes of MB and MG by Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）are chemisorption.In addition,the characterization results inferred that,the adsorption of MB and MG in aqueous solution by the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）were mainly by electrostatic interaction,pore filling and ion exchange.Besides,the adsorption processes of the decoction residues of Tetrapanacis Medulla and Prunellae Spica on MB and MG in aqueous solution also included hydrogen bonding.4.The water quality statuses of the aqueous solution were better after the adsorption of MB and MG by the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）.It indicates that the treatments of MB and MG pollutants in water by the Chinese medicine decoction residues（Paeoniae Radix Alba,Tetrapanacis Medulla and Prunellae Spica）did not cause new contamination to them and meet the selection criteria of environment-friendly biosorbents.