Journal of Colloid and Interface Science 333 (2009) 412 Contents lists available at ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis Short Communication Comments on “Adsorption of direct dyes from aqueous solutions by carbon nanotubes: Determination of equilibrium, kinetics and thermodynamics parameters” Yuh-Shan Ho * Department of Environmental Sciences, College of Environmental Science and Engineering, Peking University, Beijing, 100871, People’s Republic of China article info abstract Article history: Received 10 December 2008 Accepted 11 January 2009 Available online 12 February 2009 Keywords: Initial adsorption rate Pseudo-second-order kinetic model Intraparticle diffusion model Quotation error Two most suggested papers for pseudo-second-order kinetic model were published in 1984 and 1995 by Blanchard et al. and Ho, respectively. Blanchard et al. noted the overall exchange reaction of NH + 4 ions fixed in zeolite by divalent metallic ions in the solution using a second-order kinetic model. Ho used the pseudo-second-order kinetic model to the copper ion/peat adsorption system. The adsorption involved chemical bonding and cation exchange. In this comment citation error and quotation error were pointed.  2009 Elsevier Inc. All rights reserved. Recently, Kuo et al. [1] published the paper noted above. In Section 3.2.1, Effects of dye concentration, the authors noted a pseudo-second-order model, initial adsorption rate h, and intra- particle diffusion model. In the case of the pseudo-second-order model the authors cited two secondary materials as references [2,3]. In fact, the pseudo-second-order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been presented by Ho [4] and this kinetic expression has also been published in 1996 [5]. At the same time Ho has pre- sented a definition for the initial adsorption rate from the pseudo- second-order model. A modified model has been made in the following years because a mistake was included in the paper pub- lished in 1996 [6–8]. However, in the case of initial adsorption rate, the authors noted that “the initial adsorption rate h (mg/g min) can be determined by using the equation h = k 2 q 2 e ” without any cita- tions. In the case of the intraparticle diffusion model, the authors cited the same two secondary materials as references [2,3]. A quo- tation error of the intraparticle diffusion model was contained in DOI of original article: 10.1016/j.jcis.2008.08.038. * Fax: +86 10 62751923. E-mail address: dr_ysho@hotmail.com. both references. The equation presented in the paper could not be found in the original paper of Weber and Morris [9]. Accuracy of quotations and citations is very important for the transmission of scientific knowledge. I suggest that Kuo et al. cite the original or the most frequently cited papers for the kinetic models to have more accuracy and details of information about kinetic expression. References [1] C.Y. Kuo, C.H. Wu, J.Y. Wu, J. Colloid Interface Sci. 327 (2008) 308. [2] C.H. Wu, J. Hazard. Mater. 144 (2007) 93. [3] I.D. Mall, V.C. Srivastava, N.K. Agarwal, Dyes Pigments 69 (2006) 210. [4] Y.S. Ho, Ph.D. thesis, University of Birmingham, Birmingham, UK, 1995. [5] Y.S. Ho, D.A.J. Wase, C.F. Forster, Environ. Technol. 17 (1996) 71. [6] Y.S. Ho, G. McKay, Chem. Eng. J. 70 (1998) 115. [7] Y.S. Ho, G. McKay, Water Res. 34 (2000) 735. [8] Y.S. Ho, J. Hazard. Mater. 136 (2006) 681. [9] W.J. Weber Jr., J.C. Morris, J. Sanit. Eng. Div. ASCE 89 (1963) 31. 0021-9797/$ – see front matter  2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2009.01.025