Adsorption And Degradation Of Organic Dyes By Periphyton

Rhodamine B(RhB),also known as rose B,is a synthetic organic dye with fresh peach color.Methylene Blue(Methylene Blue,hereinafter referred to as "MB)is also called the Methylene Blue,is a kind of synthetic thiazide dye compounds;Malachite Green(MG),also known as aniline Green,is a synthetic organic compound of triphenylmethane.RhB,MB,and MG have potential carcinogenic,teratogenic and mutagenic biological toxicity.Periphyton is a kind of microbial aggregates growing on a solid matrix in water.It has strong ability in adsorption and degradation ability on organic matter.However,the adsorption and degradation characteristics of chemical dyes Rh B,MB and MG by periphyton are remain unknown.This study investigated the adsorption and degradation characteristics of RhB,MB and MG by periphyton inactivated and inactivated conditions,under a group of the dosage of periphyton,temperatures,pH values and the initial mass concentration of RhB,MB and MG.This study also investigated the degradation mechanism of RhB,MB and MG by periphyton with HPLC-MS detection.The results showed that periphyton had some functions in biosorption and degradation of RhB,MB and MG.Within the dosage of periphyton in this experiment,the removal rate towards RhB,MB and MG increased gradually with the raise of periphyton.The removal procedure of Rh B and MG by periphyton included two-stage synergistic processes,involving biosorption and biodegradation,with biosorption as the dominant process.The process of removing MB by periphyton was mainly biological adsorption.The results showed that periphyton showed removal ability on the above three organic dyes,and adsorption plays the dominant role.The maximum adsorption capacities of periphyton for Rh B,MB,and MG were 71.66 mg/g,525.10 mg/g,and 987.76 mg/g.The removal efficacy of periphyton on these three organic dyes is MG > MB > RhB.The optimal pH for removing RhB,MB and MG by inactivated periphyton was 6,7,and 7,respectively.The optimal removal temperatures were 30 °C,25 °C,and 35 °C,respectively.The optimal adsorption pH of RhB,MB and MG was 6,7 and 7 respectively.And the optimal removal temperatures were 20-30 °C,30 °C and 35 °C,respectively.The adsorption isotherms were fitted by the Langmuir model and the Freundlich model.The three adsorption processes of RhB,MB and MG by inactivated periphyton were more consistent with the Langmuir model.The results of HPLC-MS showed that the biodegradation of RhB produced an intermediate product with a molecular weight of 391.The biodegradation of MB was mainly based on bioadsorption and no degradation products were produced.Periphyton biodegradation of MG produced an intermediate with a molecular weight of 226.1,4-(methylamino)benzophenone.