The Study On The Biosorption Of Acid And Basic Dye From Aqueous Solutionusing Enteromorpha Prolifera, A Green Marine Macroalga

Dyeing wastewater may cause heavy pollution to the water environment withdirect discharge, due to the high water volume, complicated water quality, highcontent of organic substances, difficulties in biodegradation, high colority, etc.Treatment of printing and dyeing wastewater is various with different the effect.Adsorption method is in common use in the decoloration techniques of dyeing andprinting wastewater. Recently, various kinds of adsorbents have been developed in thetreatment of dyeing and printing wastewater and a good effect has been achieved.Recently, much attention has been paid on the use of macroalgae, which iswidely distributed. As an alternative biosorbent, macroalgae is favoured with rapidgrowth, rich in sources, high specific surface area. In addition, algal cell walls containabundant carbohydrates and proteins, which can provide amino, carboxylate, hydroxyl,and phosphate groups to establish bonds with dye molecules. This is a main reason formacroalgae become a promising biological material on decolorization in future.Enteromorpha prolifera, a kind of macroalgae, is flooded by the sea of Qingdao andother cities in the spring and summer. It damages the marine ecology, impairs coastallandscope and causes green tide hazards. Currently, there are no good treatment orutilization methods for Enteromorpha prolifera.There are a wide range of acid dyes in our country. Acid bordeaux B （ABB） andnylosan yellow N-3RL （NYN） are two kinds of acid dyes imported from abroad.Methylene blue （MB） is a kind of basic dye using in paper printing and cotton andfabric printing. No report is found on the adsorption of these three kinds of dyes byEnteromorpha prolifera in China.Enteromorpha prolifera power is used as the adsorbent in this study. Aninvestigatation on the adsorption properties of the above two acid and a alkaline dyes wastewater by static adsorption test are carried out. To research and discuss theoptimal adsorption conditions, including initial pH value of waste water, reactiontemperature, oscillation frequency, cantact time, does of Enteromorpha prolifera andinitial dye concentration. The result shows that:（1）While the simulated wastewater volume is100ml, the optimal adsorptionconditions of the two dyes with Enteromorpha prolifera are gained as follow: theinitial concentration of dye water is200mg L^-1, the contact time is60min, pH value4⁹, the temperature is room temperature（20³0℃）, the oscillation frequency is150rpm for ABB,100rpm for NYN, the dosage of adsorbent is0.25mg g^-1for ABB,5mg g^-1for NYN. Under the optimal conditions, the defluoridation rate of ABB andNYN are up to93.89%and41.05%, the adsorption capacity of ABB and NYN are751.13mg g^-1and8.21mg g^-1respectively. The adsorption process of ABB fits wellwith both Langmuir model and Freundlich model, the maximum adsorption capacityfor ABB is3333.33mg g^-1. While the adsorption process of NYN only fits well withFreundlich model.（2） While the simulated wastewater volume is100ml, the optimum adsorptionconditions of the basic dye of MB waste water by Enteromorpha prolifera are gainedas follow: the initial concentration of dye water is100mg L^-1, pH value is4¹1, thetemperature is room temperature （20³0℃）, the oscillation frequency is100rpm, thecontact time is90min, the dosage of adsorbent is0.125mg g^-1. Under the optimalconditions, the defluoridation rate of MB is79.91%, the adsorption capacity of MBis636.04mg g^-1. The adsorption process of MB fits well with both Langmuir modeland Freundlich model, the maximum adsorption capacity is909.09mg g^-1.（3） Sorption dynamics study reveals that the adsorption process of these threedyes with Enteromorpha prolifera follows pseudo-second-order. The sorption processis complex: liquid film boundary and intra-particle diffusion both contribute to therate-determining step. Thermodynamic studies showed that the adsorption process ofthese three dyes by Enteromorpha prolifera is an exothermic process, and elevatingtemperature is not in favour of the adsorption process. The biosorption of ABB andMB with Enteromorpha prolifera is spontaneous in nature, while the biosorption of NYN is not spontaneous in nature.（4） The adsorption of these three dyes with Enteromorpha prolifera mechanismis discussed through FT-IR analisis. Sorption mechanism demonstrates that,Enteromorpha prolifera removes ABB by means of not only chemical adsorption butalso hydrogen bonding, while Enteromorpha prolifera removes NYN and MB bymeans of only hydrogen bonding.