Study On Impurity Removal Effect And Mechanism In Extract Of Traditional Chinese Medicine By Flocculation

To remove impurities, reserve more active components of solution, improvesolution clarity and stability, flocculation technology was used to purify the herbalextract of Xiao’er Kehuanling Oral Liquid (XKOL). Based on the retention rate ofchlorogenic acid, removal rate of tannin and protein, the turbidity degree of thesupernatant solution and floc configuration, size, and fractal dimension, theinfluences of the flocculant type and dosage, flocculation temperature, mixing speedand time on flocculation effect were investigated, and the optimum flocculant andprocess conditions were obtained. In addition, the flocculation impurity removalregularity and flocculation mechanism were studied, and compared with thetraditional alcohol precipitation method, the feasibility of flocculation technical forpurification processing of XKOL extraction was discussed.Through analyzing the flocculation effect of chitosan and tannin-chitosancomposite flocculant in XKOL extraction, it was resulted that as the increase oftemperature, mixing speed and mixing time, the removal rate of impurities andsolution clarification degree increased firstly and then decreased. Chlorogenic acidretention rate was mainly influnced by flocculant type and dosage, while the rest ofoperation parameters had little effect on chlorogenic acid. The optimum flocculationprocess conditions for chitosan were as follows: the flocculation temperature was30℃, the chitosan dosage was0.75g/L, the tip velocity of propeller was1.3m/s and thefast mixing time was120s, then the tip velocity of propeller was0.26m/s and theslow mixing time was15min. The optimum flocculation process conditions fortannin-chitosan composite flocculant were as follows: the flocculation temperaturewas25℃,0.375g/L tannin was dosed in XOKL extract, stirred for1min at the tipvelocity of propeller0.26m/s followed by2min at0.13m/s, then0.5g/L chitosan wasdosed in the extract solution, stirred at0.26m/s for1min followed by a slow stirring at0.1m/s for5min.Floc size generated by tannin-chitosan complex flocculation was larger91μ mthan that of chitosan flocculation, fractal dimension of floc was increased0.056, theability of resistance shear stress and recoverability was improved4.2%and15.6%respectively, impurities removal and solution clarity was relatively higher, while theretention rate of chlorogenic acid and polysaccharide was slightly lower.Compared with ethanol precipitation, the flocculation effect of water-extraction solution of XKOL with chitosan and tannin-chitosan complex flocculation havedistinct advantages that the content of chlorogenic acid was improved6.3%and4.2%, polysaccharide was improved25.8%and23.1%, the removal rate of tannin wasimproved21.6%and48.9%, and as well as the clarity and stabilization wereincreased. Flocculation technology can be used in the purification process of theextract of XKOL.For chitosan flocculation in XKOL extract, adsorption and bridging play theleading role, together with charge neutralization and patch flocculation. Flocculationin XKOL extract by tannin-chitosan complex flocculation was mainly by thecombination of multipoint hydrogen bonding and hydrophobic binding betweentannin and protein, adsorption and bridging, associated with charge neutralization andpatch flocculation.