A process for removing heavy metal ions from aqueous solutions with an adbent comprising granules of a mixture of nitrohumic acid and at least one binder selected from the group consisting of a carboxyl group-containing polymeric compound and a water-insoluble salt thereof. These heavy metal adsorbents are produced advantageously by either a process wherein a mixture of nitrohumic acid and a carboxyl group-containing polymeric compound is kneaded with an aqueous solution of alkali and the kneaded mixture is first subjected to an acid treatment and then shaped into granules, or a process wherein nitrohumic acid and a carboxyl group-containing polymeric compound are dissolved in an aqueous solution of alkali, the solution is acidified to form a precipitate and then the precipitate is separated and shaped into granules. The granular products thus obtained can be further improved in mechanical strength by means of a heat treatment.