Abstract
Biochar derived from straw is a potential low-cost adsorbent for metal ions and organic pollutants, but its practical application is still limited by the adsorption capacity. In this study, the correlation between the biochar’s properties and pyrolysis temperature was explored. The adsorption mechanism was studied by monitoring the changes of biochar properties before and after adsorption using BET, SEM, XPS and FT-IR spectroscopy. The adsorption mechanism was revealed following the adsorption kinetics and the changes in biochar’s properties before and after adsorption. The methylene blue (MB) and Pb2+ adsorption removal efficiency reached 95% at the initial concentration of 125 and 500 mg/L, respectively. Physisorption, chemisorption, and pore filling mechanisms determined the adsorption process of MB and Pb2+ on biochar. The Pb2+ adsorption process was highly affected by chemical co-precipitation at higher pyrolysis temperatures. The appearance of tar particles increased the adsorption rate of Pb2+. The biochar obtained at the pyrolysis temperature at 500, 800 and 900°C proved to be applicable for Pb2+ removal. Chemisorption and porosity dominated the MB adsorption, and biochars produced at pyrolysis temperatures of 200, 800 and 900°C are potential materials for MB removal. This study provides optimal pyrolysis conditions for transforming maize straw into valuable, low-cost materials for the removal of different pollutants.
Highlights
Biochar is widely used, porous carbonaceous material for the purification of water/wastewater and the remediation of contaminated soil [1,2,3]
The surface morphology of maize straw-derived biochar was strongly influenced by pyrolytic temperature
The results revealed a sudden increase of methylene blue (MB) adsorption capacity of biochar produced at 200 and 800 ̊C (S200 and S800)
Summary
Porous carbonaceous material for the purification of water/wastewater and the remediation of contaminated soil [1,2,3]. Biochar is mainly obtained via pyrolysis of organic biomass under anoxic conditions [4,5,6]. With the development of slash-and-char technology, the pyrolysis of biomass is more extensively used for the production of biochar and bioenergy. Biochar represents a promising alternative to activated carbon due to the low cost [7,8,9]. The purification of soil and water depends on several properties of biochar such as surface area (SA), the abundance and type of functional groups on the surface and pore volume.
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