Al-Ghouti Mohammad A, Khraisheh Majeda A M, Ahmad Mohammad N M, Allen Stephen
Industrial Chemistry Centre, Royal Scientific Society, Amman, Jordan.
J Hazard Mater. 2009 Jun 15;165(1-3):589-98. doi: 10.1016/j.jhazmat.2008.10.018. Epub 2008 Oct 14.
The effect of initial concentration, particle size, mass of the adsorbent, pH and agitation speed on adsorption behaviour of methylene blue (MB) onto Jordanian diatomite has been investigated. The maximum adsorption capacity, q, increased from 75 to 105 mg/g when pH of the dye solution increased from 4 to 11. It is clear that the ionisable charge sites on the diatomite surface increased when pH increased from 4 to 11. When the solution pH was above the pH(ZPC), the diatomite surface had a negative charge, while at low pH (pH<5.4) it has a positive charge. The adsorption capacity increased from 88.6 to 143.3mg/g as the initial MB concentrations increased from 89.6 to 225.2mg/dm(3). The experimental results were also applied to the pseudo-first and -second order kinetic models. It is noticed that the whole experimental data of MB adsorption onto diatomite did not follow the pseudo-first order model and had low correlation coefficients (R(2)<0.3). The calculated adsorption capacity, q(e,cal), values obtained from pseudo-first order kinetic model did not give acceptable values, q(e,exp.) The maximum uptake capacity seems to be independent of the particle size of the diatomite when the particle size distribution is less than 250-500 microm. While at larger particle size 250-500 microm, the maximum uptake capacity was dependent on the particle size. It would imply that the MB adsorption is limited by the external surface and that intraparticle diffusion is reduced. The effect of the agitation speeds on the removal of MB from aqueous solution using the diatomite is quite low. The MB removal increased from 43 to 100% when mass of the diatomite increased from 0.3 to 1.7 g.
研究了初始浓度、粒径、吸附剂质量、pH值和搅拌速度对约旦硅藻土吸附亚甲基蓝（MB）行为的影响。当染料溶液的pH值从4增加到11时，最大吸附容量q从75增加到105mg/g。显然，当pH值从4增加到11时，硅藻土表面的可电离电荷位点增加。当溶液pH值高于零电荷点（ZPC）时，硅藻土表面带负电荷，而在低pH值（pH<5.4）时带正电荷。随着初始MB浓度从89.6增加到225.2mg/dm³，吸附容量从88.6增加到143.3mg/g。实验结果还应用于准一级和二级动力学模型。注意到MB吸附到硅藻土上的整个实验数据不遵循准一级模型，且相关系数较低（R²<0.3）。从准一级动力学模型获得的计算吸附容量q（e，cal）值未给出可接受的q（e，exp.）值。当粒径分布小于250 - 500微米时，最大吸附容量似乎与硅藻土的粒径无关。而在较大粒径250 - 500微米时，最大吸附容量取决于粒径。这意味着MB的吸附受外表面限制，颗粒内扩散减少。搅拌速度对使用硅藻土从水溶液中去除MB的影响相当小。当硅藻土质量从0.3增加到1.7g时，MB去除率从43%增加到100%。
