Cu²⁺ Adsorption By Brewers' Yeast Biomass: The Effect Of Ethanol, Caustic And Nano-titania Modification

With the striking development of some industries in our country such as steel production,electroplateing,leather tanning,nuclear power plant etc.,there exists a severe water resource crisis due to a large amount of water contaminated by heavy metals.The discharge of heavy metals contained in waste water not only causes the waste of water resources but also influences the safety of drinking water.Therefore,the research on disposing heavy metal ions in waster water has quite practical application significance for resolving the water resource crisis and promoting the intensive development of industry, such as leather tanning,mining,smelting,electroplating,etc.In the commonly used processes for removing heavy metal ions from industrial effluents,the biosorption attract extensive attention,increasingly since it has some advantage including good effect on removing heavy metal ions,convenient operation and low cost and no secondary contamination.In addition,the nanometer material,a novel functional material with some extraneous characteristic such as large specific surface,high surface energy,high chemical activity,etc.,attracts much more attention to field of environmental protection.In the experiment,brewers' yeast biomass was modified by ethanol/caustic treatment, respectively,and then the three biomass samples were utilized as biosorbents to adsorb Cu²⁺ in the aqueous solution.All the effect condition on adsorption,such as pH value, contact time,initial concentration of Cu²⁺,coexisting ions and elution experiment,were discussed and the results show that the Cu²⁺ adsorption capacity of the adsorbent follows this decreasing order:caustic＞ethanol＞initial.In additional,all of these adsorbing processes fit very well with the model of the Langmuir isotherm.After these adsorbents (with/without Cu²⁺) were tested and analyzed,the investigations indicated that these active groups(carboxyl,amido,hydroxyl,carbonyl,phosphoryl,etc.) played a very important role in the process of removing Cu²⁺ and the quantity of active groups on brewers' yeast cell walls were apparently enhanced by the method of ethanol/caustic modification.The elution experiment showed that both reversible and irreversible adsorption occurred simultaneously in the adsorption process.However,the reversible adsorption had a greater affect on the process.The anatase nano-TiO₂ powder,with crystal size between 40 and 80 nm,was prepared by the liquid phase hydrolysis of TiCl₄ and its disposal to Cu²⁺ is investigated in/under darkness and UV-illumination.The effect factor,such as reaction time,pH value and Zeta potential etc.,on removal of Cu²⁺ was researched and the results showed that the highest removal efficiency of Cu²⁺ by nano-titania were 54.4%and 68.2%,respectively.In addition,the removal efficiency was improved by reductive organics according to the order HCOOH＞HCHO＞CH₃OH under UV-illumination but decreased in darkness.The different effect on removal Cu²⁺ was made by different coexisting anions in the solution.In the study,the nano-TiO₂ was utilized with the brewers' yeast biomass as a composite adsorbent to adsorb Cu²⁺ in the aqueous solution.The investigation showed that the composite adsorbent had a fine adsorption efficiency.The TiO₂ in the composite adsorbent could cooperate well with brewers' yeast to improve the adsorbing capability of Cu²⁺.In addition,the results of measurements,obtained with a scanning electron microscope,an infrared spectrophotometer and a Zeta potential analyzer,revealed that the brewers' yeast and nano-TiO₂ produced the composite adsorbent through coordination and hydrogen bonds in particular,etc.The stability of the composite adsorbent and the amount of titania loaded were largely dependent on the concentration of hydrogen ion in the solution.