Efficient corn straw and poplar leaf biochar-based adsorbents for the eradication of methylene blue from aqueous solutions

Abstract

Using agricultural and forestry waste biomasses as raw materials for the removal of organic dyes from wastewater is a cost-effective approach for environmental purification. In this paper, corn straws and poplar leaves were carbonized at different temperatures for 3 h to produce biochar-based adsorbents. Afterwards, with the addition of the prepared adsorbents to methylene blue (MB) waste-water, the effects of contact time, initial concentration of MB and adsorbent dosage on the adsorption performance were investigated. Meanwhile, both adsorption kinetic models and adsorption isotherm models were also studied to explore adsorption mechanisms of the obtained adsorbents. The physico-chemical properties of biochar-based adsorbents were subsequently characterized by scanning electron microscopy and Brunauer–Emmett–Teller. The results demonstrated that two bio-char-based adsorbents produced from corn straws and poplar leaves at 300°C after 3 h carbonization achieved the highest yields of 90.5% and 90.7%, respectively. The removal rate of MB increased with contact time and the adsorption capacity for MB enhanced with initial concentration of MB by biochar-based adsorbents prepared by corn straws and poplar leaves. The highest removal rate of MB was 99.2% for corn straws biochar-based adsorbent at a dosage of 1.0 g and 95.1% for poplar leaves biochar-based adsorbent at a dosage of 1.5 g. Furthermore, the adsorption process of MB by corn straw and poplar leaf biochar-based adsorbents conformed to the quasi-second-order adsorption kinetic model and Langmuir model, which was dominated by chemical adsorption.