Comments on “Preparation and application of 4-amino-4′-nitro azobenzene modified chitosan as a selective adsorbent for the determination of Au(III) and Pd(II)”

Abstract

Recently, Wang et al. published the paper entitled “preparation and application of 4-amino-4′-nitro azobenzene modified chitosan as a selective adsorbent for the determination of Au(III) and Pd(II)” [1]. In section “Adsorption kinetics”, the authors presented the term “original rate” as “h stands for original rate of reaction which can be defined as h 1⁄4 k2qe .” without any citations. In fact, the definition of initial adsorption rate (original rate) for the adsorption systems of divalent metal ions using sphagnum moss peat has been presented by Ho [2], and this expression has also been published in 1996 [3]. A modified initial adsorption rate has been presented in 1998 to correct a mistake that was included in the previous paper published in 1996 [4–6]. These papers should be cited. Another quotation error is that the authors cited Atia [7] and Merrifield et al. [8] regarding the pseudo-secondorder kinetic equation while nothing about “the pseudosecond-order kinetic equation” was mentioned in these two references. Two most suggested papers for the pseudosecond-order kinetic equation were published in 1984 and 1995 by Blanchard et al. [9] and Ho [2, 6], respectively. Blanchard et al. noted the overall exchange reaction of NH4 + ions fixed in zeolite by divalent metallic ions in the solution using a second-order kinetic model [9]. Ho used the pseudo-second-order kinetic model to the copper ion/peat adsorption system. The adsorption involved not only cation exchange but also chemical bonding [2]. When a scientific publication duplicate previously published idea, text, equations, or figures without any citations, it frequently is regarded as a sign of possible plagiarism [10]. To avoid being misconstrued, as well as to provide more accurate information, I would suggest that the authors cite the original paper for the initial adsorption rate.