Well-crystalline homogeneous alpha-Fe2O3 nanopeanuts were synthesized, characterized and utilized as an effective photocatalysts for the photocatalytic degradation of toxic and harmful organic dyes, i.e. Congo red (CR), Eosin red (ER) and methylene blue (MB). The nanopeanuts were synthesized by facile one-step hydrothermal process without employing any templates and characterized in detail in terms of their morphological and structural properties. The detailed characterizations confirmed the well-crystallinity, large-scale growth and rhombohedral crystal structure of the synthesized nanopeanuts. Further, the detailed growth processes of prepared nanopeanuts were studied by examining the effects of reaction time, temperature and amounts of hexamethylenetetramine (HMT) on the shapes and sizes of the products. Thus, based on the observed experimental evidences, a possible growth mechanism for the formation of nanopeanuts was also proposed. Finally, the nanopeanuts were used as efficient visible-light driven photocatalyst for the photocatalytic degradation of organic dyes and the observed degradation rates were MB (57%) < ER (63%) < CR (93%) under visible-light irradiation. Interestingly, it was seen that the photocatalytic degradation of nanopeanuts was higher than other alpha-Fe2O3 nanostructures such as nanospindles and commercial alpha-Fe2O3 which revealed that the prepared alpha-Fe2O3 nanopeanuts are excellent visible-light driven photocatalyst for the photocatalytic degradation of harmful and toxic organic dyes. (C) 2015 Elsevier Inc. All rights reserved.