The Preparation Of Magnetical Microalgae And Its Decolorization Of Congo Red And Methylene Blue

Dyeing wastewater may cause heavy pollution to the water environment with direct discharge due to its high water volume,complicated water quality,high content of organic substances,difficulties in biodegradation,etc.Treatment mothods of dyeing wastewater are various.Adsorption method has many adavantages in the decoloration techniques of dyeing wastewater.Microalgae are tiny single-celled autotrophs,the biggest advantage of microalgae is that its cultivation cost is much lower than the others.Microalgae cell walls contain abundant carbohydrates and proteins,which can provide amino,carboxylate,hydroxyl,and phosphate groups to establish bonds with dye molecules,this is a main reason for microalgae becoming a promising biological material on decolorization in future.But the application of microalgae is restricted because of its small powder particles and the difficulty to realize solid-liquid separation.Therefore,the key problem is how to exploit a new technique to make the adsorbent separate easily and put it into practice.In order to solve the solid-liquid separation problem of microalgae which is used as adsorbent,in this study,Magnetic Fe3O4 nanoparticles were prepared through chemical coprecipitation method using FeCl3·6H2O,FeSO4·7H2O and NH3·H2O,then magnetic Chlorella pyenoidosa(M-Cp)and Spirulina platensis(M-Sp)composites were prepared by surface adhesion method through the combination of water-based magnetic fluids and Chlorella pyenoidosa(Cp)and Spirulina platensis(Sp)powder respectively.XRD characterization results show that the magnetic nanoparticles were successfully loaded on the surface of microalgae cells,magnetic microalge has characteristics of superparamagnetism,and good physical and chemical stability.In order to study the potential removal rate and the mechanism of the adsorption,Congo red(CR)and methylene blue(MB)dye wastewater were used as objects.At room temperature with initial pH of 7,the maximum adsorption capacity of CR on absorbents with Cp,M-Cp,Sp,M-Sp was 169.468,135.905,118.469,103.140 mg/g respectively.The maximum adsorption capacity of MB on absorbents with Cp,M-Cp,Sp,M-Sp was 216.908,200.725,186.304,193.502 mg/g respectively.The studies of microalgae and magnetic microalgae adsorbents for two kinds of dye wastewater sorption dynamics reveals that the adsorption processes of these dyes with microalgae follows pseudo-second-order.Thermodynamic studies showed that the adsorption process of CR by adsorbents is an endothermic process and the adsorption process of MB is an exothermic process.The adsorption of these two dyes with adsorbents mechanism is discussed through FT-IR analysi.Sorption mechanism demonstrates that these adsorbents remove CR and MB by means of not only chemical adsorption but also hydrogen bonding.