Arid and semi-arid areas are attractive for the development of solar thermal energy due to the abundance of solar energy. However, these regions are also known for their limited access to water and water sources. A shared challenge in the arid and semi-arid areas of the United States and Mexico is the contamination of water sources with arsenic, which poses an important challenge for the sustainability of the communities in these areas. Having access to these contaminated water sources could facilitate the management of water supplies and reduce the over-exploitation of other wells, facilitating at the same time the installation of solar power plants. The arrival of engineered nanomaterials has opened unprecedented opportunities in the development of nanofluids that can be used to improve the heat transport in solar thermal energy but also as adsorbent materials for water treatment since they face common challenges such as stability. In this work we show the development of graphene and graphene oxide for both applications. We show that is feasible to produce graphene by wet attrition milling by controlling the milling conditions and by selecting solvents with high contact angles. Furthermore, we observed that although graphene oxide can be used to produce stable nanofluids to adsorb arsenic (adsorption capacity of 35 mg/g) the presence of secondary salts, such as carbonates (common salts in the region), leads to the formation of agglomerates, thus inhibiting any arsenic adsorption. In order to overcome this challenge and increase the selectivity of graphene oxide towards arsenic while maintaining their stability in water, we functionalized graphene oxide with SH and SO3H groups using sulfuric acid, cysteamine and sulfanilic acid and characterized the samples with FTIR, XPS, Raman spectroscopy, SEM and TEM. We observed that the functionalization of graphene oxide can produce relatively stable nanofluids despite the presence of secondary salts, while increasing almost the double the adsorption capacity of GO towards arsenic, making it a useful material for energy generation and water treatment.