Methylene Blue Removal By Coupling BC Adsorption With TiO₂ Photodegradation

With the development of the social economic,industries discharged large amount of dyes wastewater that were difficult to be degraded because of the high chroma,high toxicity.The aim of this study is to remove methylene blue(MB) by coupling Black carbon(BC) adsorption with TiO₂ photodegradation.BC is defined as the highly carbonaceous polymeric materials produced from incomplete combustion of fossil fuel and biomass.It exists in all the environmental media including atmosphere,hydrosphere,biosphere,soil and rock.With abundant surface functional groups and high surface area to be similar with that of the active carbon,BC is determined to have an extensive applicable adsorption prospect for organic pollutants.Firstly,adsorption kinetics and thermodynamics of Methylene Blue by black carbon was studied by batch experiments.The main influential factors included temperature, initial concentration,pH Values,and Oscillation.The adsorption isotherms fitted well to Langmuir and Freundich equation and the latter one is better suited.This indicated that the adsorption was multilayer adsorption.The parameters n＞1 show that the reactions are preferential process under different temperature.The thermodynamics study indicates that the positive value ofâ–³H shows an endothermic process,and the negative value ofâ–³G shows the spontaneous nature of the adsorption process,and the positive value ofâ–³S indicates the increased randomness at the solid/solution interface during the adsorption processes.The results showed that the adsorption rate for the solute appeared to be the second order kinetics and the intraparticle diffusion was the main rate-controlling step.Secondly,it is the best treatment efficiency for methylene blue removal by coupling BC adsorption with TiO₂ photodegradation resulting from the analysis of multiple-factor experiments.The effects of various factors such as the amount of TiO₂,the amount of BC, illumination intensity,initial concentration and pH Values on the photocatalytic behavior for MB were discussed.The opt condition for 50 mg/L dye solution degradation was TiO₂ 0.5 g/L,BC 0.2 g/L,illumination intensity 3.7 mW/cm².In the alkaline condition,the more efficient degradation occurs than that in the acidic environment.Different electrolyte solutions hinder the experimental process.Compared with four electrolyte ions,the degradation effect is PO₄³ï¼žNO₃＞SO₄²ï¼žCl^-. Finally,this study explained clearly the synergy effect of BC adsorption and TiO₂ photocatalysis,i.e.low concentration pollutants are enriched in the catalyst's surface by BC adsorption.It provides the micro-environment of the high concentration pollutants for TiO₂ degradation.Meanwhile,BC can adsorb the intermediate products simultaneously in the course of photodegradation,then in favor of the further photocatalytic degradation. After complete degradation,the dye is mineralized as CO₂,H₂O,and departure from the sorbent surface then the sorbents are regenerated.The synergy effect is the combination processes of adsorption,enrichment,photocatalysis and regeneration.