Adsorbents and Methods used for effective removal or concentration or retention and recovery of harmful or valuable dissolved ions and compounds from aqueous systems using quantum size effect on large band gap semiconductors are provided. This invention provides methods for creating surface hydroxyl groups on surfaces of anatase, brookite and rutile large band gap semiconductors which comprise methods of reducing dimensions of individual crystals to the sizes where surface hydroxyl groups are self generated via quantum size effects when they contacted with electrolytes. This invention also provides methods of reproducible preparation of quantum sized effected anatase, brookite and rutile, which comprise in non-batch and continues process in which growth of said crystals is aborted. The invention also provides methods using quantum size effected anatase, brookite and rutile products for treatment of water, comprising rapid and high capacity adsorption of dissolved molecules and ions to the surface of said crystals via surface reaction process between said effect created hydroxyl groups with molecules and ions. Invention in general provides an effective means for treatment of water from harmful contaminants, especially As, P, U, transuranic elements, W, Mo, Cu, Pb, Cd, Co, Ni, Cr and others