Activated carbon derived from highland barley straw for removing heavy metals and organic pollutants

Biomass activated carbon has been widely used in the field of wastewater treatment because of its unique properties, such as high specific surface area and porosity, good adsorption capacity, good mechanical strength, rich functional groups and thermal stability. In this work, highland barley straw is recycled and made into activated carbon using hydrothermal carbonization and alkaline activation processes in which the dependence of the product properties on the activation temperature, as one of the critical parameters, is intensively investigated. Under the optimum conditions at an activation temperature of 1100°C, activated carbon in the form of mesoporous structure and polycrystalline graphite was produced with a specific surface area as large as 1906 m2/g, which is superior to that of commercial products. To investigate the absorption capacity of the prepared samples for pollutants in water, such as heavy metals and organics, potassium dichromate and methylene blue were utilized as the simulated pollutants. The removal efficiency of Cr6+ and methylene blue in water reached 90.3% within 8 hours and 87.7% within 4 hours, respectively, and this demonstrated an excellent absorption capacity for activated carbon converted from agricultural waste. The successful fabrication of activated carbon with a super large specific surface area and remarkable adsorption ability derived from highland barley straw through a hydrothermal carbonization and alkaline treatment demonstrated the feasibility of the ‘turning waste into wealth’ recycling strategy. It has also shown great potential for use in environmental protection applications, especially for water purification.