For the valorisation of metal hydroxide sludge as adsorbent of pollutant, it is necessary to make sure that the adsorption matrix (sludge) has characteristics allowing a reproducibility of the valorisation operation. Taking into account the heterogeneity of this solid waste in terms of nature and metal chemical composition, it is necessary to establish if this heterogeneity will have important consequences on the adsorption yield of these sludge. Thus, the study, is relative to the influence of the composition of metal hydroxide sludge on their adsorption properties. Two sampling procedures are studied: sampling in a continuous way at the drying step or by coring of the final sludge heap. In order to compare the properties of adsorption, each sample is tested according to a definite adsorption protocol. In addition, this study makes it possible to compare the two sampling procedures and to determine their relevance to the sample technique. The first results show that the methods make it possible to obtain close results, both for adsorption and sludge composition. Moreover, successive quartering permits to have a representative sample in terms of metal composition.