Akhtar Mubeena, Moosa Hasany S, Bhanger M I, Iqbal Shahid
National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro-76080, Pakistan.
J Hazard Mater. 2007 Mar 22;141(3):546-56. doi: 10.1016/j.jhazmat.2006.07.016. Epub 2006 Jul 14.
Moringa oleifera pods Lamarck (Drumstick or Horseradish) is a multipurpose medium or small size tree from sub-Himalayan regions of north-west India and indigenous to many parts of Asia, Africa, South America, and in the Pacific and Caribbean Islands. Its pods (MOP) have been employed as an inexpensive and effective sorbent for the removal of organics, i.e., benzene, toluene, ethylbenzene and cumene (BTEC) from aqueous solutions using HPLC method. Effect of different parameters, i.e., sorbent dose 0.05-0.8g, 25cm(-3) agitation time 5-120min, pH 1-10, temperature 283-308K and concentration of sorbate (1.3-13)x10(-3), (1.1-11)x10(-3), (0.9-9)x10(-3), (0.8-8)x10(-3)moldm(-3), on the sorption potential of MOP for BTEC have been investigated. The pore area and average pore diameter of the MOP by BET method using nitrogen as a standard are calculated to be 28.06+/-0.8m(2)g(-1) and 86.2+/-1.3nm respectively. Freundlich, Langumir and Dubinin-Radushkevich (D-R) sorption isotherms were employed to evaluate the sorption capacity of MOP. Sorption capacities of BTEC onto MOP have been found to be 46+/-10, 84+/-9, 101+/-4, 106+/-32mmolg(-1) by Freundlich, 8+/-0.1, 9+/-0.1, 10+/-0.3, 9+/-0.1mmolg(-1) by Langumir and 15+/-1, 21+/-1, 23+/-2, 22+/-3mmolg(-1) by D-R isotherms respectively, from BTEC solutions at 303K. While the mean energy of sorption process 9.6+/-0.3, 9.2+/-0.2, 9.3+/-0.3, 9.5+/-0.4kJmol(-1) for BTEC is calculated by D-R isotherm only. Rate constant of BTEC onto MOP 0.033+/-0.003, 0.030+/-0.002, 0.029+/-0.002, 0.027+/-0.002min(-1) at solution concentration of 1.3x10(-3), 1.1x10(-3), 0.9x10(-3) and 0.8x10(-3)moldm(-3) and at 303K have been calculated by employing Lagergren equation. Thermodynamic parameters DeltaH -8+/-0.4, -10+/-0.6, -11+/-0.7, -11+/-0.7kJmol(-1), DeltaS -22+/-2, -26+/-2, -27+/-2, -29+/-3Jmol(-1)K(-1) and DeltaG(303K) -0.9+/-0.2, -1.9+/-0.2, -2.3+/-0.1 and -2.6+/-0.2kJmol(-1) were also estimated for BTEC respectively at temperatures 283-308K. The negative values of DeltaH, DeltaS and DeltaG suggest exothermic, stable (with no structural changes at solid-liquid interface) and spontaneous nature of sorption process under optimized conditions. MOP has been used extensively to accrue and then to preconcentrate benzene, toluene and ethylbenzene in wastewater sample.
辣木豆荚（辣木或山葵）是一种多用途的中小型树木，原产于印度西北部的喜马拉雅地区，在亚洲、非洲、南美洲以及太平洋和加勒比群岛的许多地方都有分布。其豆荚（MOP）已被用作一种廉价且有效的吸附剂，采用高效液相色谱法从水溶液中去除有机物，即苯、甲苯、乙苯和异丙苯（BTEC）。研究了不同参数，即吸附剂剂量0.05 - 0.8g、25cm³搅拌时间5 - 120分钟、pH值1 - 10、温度283 - 308K以及吸附质浓度（1.3 - 13）×10⁻³、（1.1 - 11）×10⁻³、（0.9 - 9）×10⁻³、（0.8 - 8）×10⁻³mol dm⁻³对MOP吸附BTEC潜力的影响。以氮气为标准，通过BET法计算出MOP的孔面积和平均孔径分别为28.06 ± 0.8m² g⁻¹和86.2 ± 1.3nm。采用Freundlich、Langumir和Dubinin - Radushkevich（D - R）吸附等温线来评估MOP的吸附容量。在303K下，通过Freundlich等温线测得BTEC在MOP上的吸附容量分别为46 ± 10、84 ± 9、101 ± 4、106 ± 32mmol g⁻¹，通过Langumir等温线测得为8 ± 0.1、9 ± 0.1、10 ± 0.3、9 ± 0.1mmol g⁻¹，通过D - R等温线测得为15 ± 1、21 ± 1、23 ± 2、22 ± 3mmol g⁻¹。仅通过D - R等温线计算出BTEC吸附过程的平均能量为9.6 ± 0.3、9.2 ± 0.2、9.3 ± 0.3、9.5 ± 0.4kJ mol⁻¹。在303K下，采用Lagergren方程计算出在溶液浓度为1.3×10⁻³、1.1×10⁻³、0.9×10⁻³和0.8×10⁻³mol dm⁻³时，BTEC在MOP上的吸附速率常数分别为0.033 ± 0.003、0.030 ± 0.002、0.029 ± 0.002、0.027 ± 0.002min⁻¹。在283 - 308K温度下，还分别估算了BTEC的热力学参数ΔH为 - 8 ± 0.4、 - 10 ± 0.6、 - 11 ± 0.7、 - 11 ± 0.7kJ mol⁻¹，ΔS为 - 22 ± 2、 - 26 ± 2、 - 27 ± 2、 - 29 ± 3J mol⁻¹ K⁻¹，以及ΔG(303K)为 - 0.9 ± 0.2、 - 1.9 ± 0.2、 - 2.3 ± 0.1和 - 2.6 ± 0.2kJ mol⁻¹。ΔH、ΔS和ΔG的负值表明在优化条件下吸附过程是放热的、稳定的（固液界面无结构变化）且自发的。MOP已被广泛用于富集然后预浓缩废水样品中的苯、甲苯和乙苯。
