Comments on: “Comparison of reductive dechlorination of p-chlorophenol using Fe and nanosized Fe 0 0 .” By R. Cheng et al. J. Hazard. Mater. 144 (2007) 334. C. Noubactep Centre of Geosciences, University of Göttingen, Goldschmidtstraße 3, D - 37077 Göttingen, Germany. e-mail: cnoubac@gwdg.de ; Tel. +49 551 39 3191, FAX: +49 551 399379 The article of Cheng and colleagues [1] was intrinsically interesting as its intended to compare the efficiency of conventional Fe (mm to μm size) 0 and nanosized Fe for aqueous reductive dechlorination of 0 p-chlorophenol. Such investigations are necessary to gain more details on the expected reactivity of nanosized Fe . In fact, the introduction of nanosized Fe in groundwater remediation was not univocal [2]. Therefore, such comparative works from the same research group should be very helpful. 0 0 Unfortunately, due to the lack of a unified procedure for conducting contaminant removal experiments in investigating processes in Fe 0 –H 2 O systems (here Fe 0 , 4-CP, H 2 O, O 2 ), almost any researcher uses a different experimental procedure. This deficiency has accounted for controversial results in other branches of science [3,4]. For example, Büchler et al. [3] have found out that the strong influence of the hydrodynamic conditions due to mixing operations explains many contradictory literature results on the process of the formation, growth, and dissolution of the passive film on iron in neutral and alkaline solutions. Despite the failure of a unified procedure, used experimental conditions should be rationalized either by the objective of the study or by field situations to be mimicked. These factors include [5,6]: elemental composition of used Fe 0 materials, Fe 0 pre-treatment (e.g., acid wash), Fe 0 particle size (mm, μm, nm), buffer application, the molar ratio of Fe 0 to contaminant (Fe 0 mass loading and initial contaminant concentration), volume of the bottles used in the experiment, volume of model solution added, mixing operations (bubbling, shaking, stirring), geometry of the reaction vessel, experimental duration or reaction time. 1