The objective of this study is to investigate the effect of pH variation from 3 to 12 on adsorption of Se and Co on synthetic goethite and nano particles zero-valeant iron. Therefore, series of well-controlled laboratory experiments were carried out on the previous materials. Maximum adsorption on goethite and nano particles zero-valeant iron (nZVI) for selenate occurred at the initial concentration of 10µg Se mL^-1 where nearly 99.8% and 100% of the total applied selenate  was adsorbed at a pH range of 3-4 for goethite and pH 3 for (nZVI). With increasing pH to more than 4, selenate adsorption tended to decline sharply to be 3.3% and 3.5% of the total Se added at pH 11 for goethite. Selenate adsorption decreased almost linearly from almost 3119.7 µg g^-1 goethite at pH 3.0 to 104.4 µg g^-1 goethite at pH 11 and corresponding to 24855 µg g^-1 (nZVI) at pH4.0 to 4160 µg g^-1 nZVI at pH11. The lower adsorption of selenate at high pH values is probably attributed to an increase in repulsion between the more negatively selenate species and negatively charged surface sites. Adsorption of Co showed an opposite behavior to selenate as its adsorbed quantities increased with increasing pH. The highest Co adsorption was noticed at pH 8.0 with a constant adsorption values with pH> 9.0. The highest Co adsorption was 2771 µg g^-1 goethite and 20240  µg g^-1 (nZVI), which corresponded to 89% and 81% of total added Co for goethite and (nZVI), respectively.