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In this work, a natural clay (Mn) modified with γ-aminopropyltrimethoxysilane (Mn-S) and silver (Mn-S-Ag) were evaluated as a potential adsorption media for nitrate removal from water. The natural and modified clays were characterised by FTIR, XRD, zeta-potential, TGA/DTA, SEM and elemental analyses. First, the adsorption capacity of the Mn-S clay for Ag(+) was studied. From the results, the cation adsorption capacity was almost three times greater for Mn-S than for Mn because a metal-amino group complex formation is favored when silver cations and amino groups (-NH2) are contacted. Second, the nitrate adsorption on Mn-S and Mn-S-Ag were studied as a function of contact time, pH, temperature and adsorbent dosage using batch techniques. In the absence of Ag(+), NO3(-) adsorption was high at low pH and the amount of adsorbed nitrate decreased as the pH increased, which indicates the presence of electrostatic interactions between the anion and protonated amine groups. The results showed that both clays (Mn-S and Mn-S-Ag) can retain an important amount of nitrate ions compared with previously reported data. For the Mn-S clay, the following monolayer adsorption capacities were obtained: Qmax=0.80, 0.72 and 0.68 mmol NO3(-)/g at pH 3, 5, and 7, respectively; whereas for the Mn-S-Ag clay, the values obtained were: Qmax= 0.77, 0.74 and 0.42 mmol NO3(-)/g at pH 3, 5, and 7, respectively. From the results obtained in this work, NO3(-) adsorption occurs over -NH3(+) surface groups without involving the Ag(+) cation in the adsorption process. This cation is not a promoter of nitrate adsorption. Aminopropyltrimethoxysilane- and aminopropyltrimethoxysilane-silver-modified montmorillonite for the removal of nitrate ions. Available from: https://www.researchgate.net/publication/296624200_Aminopropyltrimethoxysilane-_and_aminopropyltrimethoxysilane-silver-modified_montmorillonite_for_the_removal_of_nitrate_ions [accessed May 4, 2017].