六方水钠锰矿对罗丹明B的去除效果及机理

六方水钠锰矿作为环境中一种具有较强氧化与吸附能力的氧化锰矿物,对环境中的有机染料有着一定的去除作用。采用常压回流法一步合成纳米六方水钠锰矿,运用X射线衍射(XRD)、电感耦合等离子体光谱仪(ICP-AES)、BET氮气吸附法、场发射扫描电镜(FESEM)和透射电镜(TEM)对其矿物晶体结构、化学组成、比表面积、孔径分布和微观形貌进行表征,选用罗丹明(RB)作为目标有机染料,研究反应条件对纳米六方水钠锰矿对RB的去除效果的影响(包括pH值、六方水钠锰矿浓度、染料浓度和温度)。进而研究六方水钠锰矿对RB的去除机制,通过在反应后的溶液中加入盐酸羟胺,使矿物溶解,吸附在矿物上的染料重新释放到溶液中,以区分吸附去除率和氧化去除率。结果表明,降低反应pH、增加六方水钠锰矿浓度、减小染料浓度以及提高温度均有利于六方水钠锰矿对罗丹明B(RB)的去除。其中影响最大的pH,反应体系pH为2.87时,RB的去除率达到99.9%,而pH为10.29时,RB的去除率仅为8.33%。通过去除机制实验结果表明,在pH为4.5时,RB的氧化去除率是36.3%,吸附去除率为4.6%,六方水钠锰矿去除RB以氧化去除为主。纳米六方水钠锰矿材料的重复利用效果很好,重复使用3次去除率,RB的去除率仅从90.6%降至85.9%。合成的纳米六方水钠锰矿有着很好的去除有机染料的效果,并且有一定的重复利用性,机制的研究也有利于提升对有机染料的去除效果。

Decolorization of Rhodamine B by Hexagonal Birnessite and Its Mechanism

As a kind of manganese oxide mineral with strong oxidation and adsorption capacity in the environment,hexagonal birnessite have the ability to remove organic dyes in the environment.In this paper,nanometer hexagonal birnessite is synthesized by atmospheric pressure reflux method,and it is applied to synthesis of nano hexagonal birnessites.By applying X-ray diffraction(XRD),inductively coupled plasma spectrometer(ICP-AES)and BET nitrogen adsorption method,Field Emission Scanning Electron Microscopy(FESEM)and Transmission Electron Microscopy(TEM),its mineral crystal structure,chemical composition,specific surface area,pore size distribution and microstructure were characterized.Rhodamine B organic dye(RB)was selected as the target organic dye to study the effect of reaction conditions on the removal effect of nano-hexagonal birnessite to RB including pH,hexagonal birnessite concentration,dye concentration,and temperature.Furthermore,the mechanism of RB removal by hexagonal birnessite was studied.By adding hydroxylamine hydrochloride into the solution after the reaction,the mineral was dissolved,and the dye adsorbed on the mineral was re-released into the solution to distinguish the adsorption removal rate and oxidation removal rate.The result shows that lowering the reaction pH,increasing the concentration of hexagonal birnessite,reducing dye concentration,and increasing the temperature have positive effects on the removal of rhodamine B(RB)by hexagonal birnessite.Among them,the most influential factor was reaction pH.When the pH value of the reaction system was 2.87,the removal rate of RB reached 99.9%,while when the pH value was 10.29,the removal rate of RB was only 8.33%.The experimental results of removal mechanism show that at pH of 4.5,the oxidation removal rate of RB is 36.3%and the adsorption removal rate is 4.6%.The removal of RB by hexagonal birnessite is mainly oxidative removal.The nano-hexagonal birnessite material has a good re-use effect,with three times of removal rate,and the removal rate of RB only decreased from 90.6%to 85.9%.The synthesized nano-hexagonal birnessite has a good removal effect of organic dyes and has a certain reusability.The study of the mechanism is also conducive to improving the removal effect of organic dyes.