Surface characterization of maize-straw-derived biochar and their sorption mechanism for Pb2+ and methylene blue

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 Pb 2+ 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 Pb 2+ on biochar. The Pb 2+ adsorption process was highly affected by chemical co-precipitation at higher pyrolysis temperatures. The appearance of tar particles increased the adsorption rate of Pb 2+. The biochar obtained at the pyrolysis temperature at 500, 800 and 900˚C proved to be applicable for Pb 2+ 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.

Using magnetite/zirconium-comodified attapulgite as a novel phosphorus (P) sorbent for the efficient removal of P and the adsorption mechanism allowing this effect

“…The results indicated that the experimental adsorption data of Fe/ ZrATP were better fitted by the pseudo-second-order model (R 2 = 0.966) (Table 3). Moreover, the theoretical adsorption capacity (q e ) calculated by this model was closer to the experimental value, further confirming that the pseudofirst-order kinetic model was better and that chemisorption dominated the adsorption process (Guo et al 2020). In the initial stages of adsorption, the adsorption amount increased rapidly because the abundant adsorption sites on the surface of Fe/ZrATP were adsorbed with phosphate.…”

Preparation of Porous Biochar from Soapberry Pericarp at Severe Carbonization Conditions

“…Concerning its porous structure and surface characterization, biochar has high adsorption potential for the removal of pollutants from water streams [3][4][5][6][7]. In recent years, there is an increasing interest in exploiting biochar as an excellent carbon material for environmental applications, or reusing different lignocellulosic feedstocks for producing biochar with high pore properties (e.g., specific surface area), which includes wood [8], oil palm shell [9], maize straw [10], cocoa pod husk [11], rice husk [12] and so on.…”

Versatile Strategy for the Preparation of Woody Biochar with Oxygen-Rich Groups and Enhanced Porosity for Highly Efficient Cr(VI) Removal

“…Lastly, the peaks between 1050 and 1093 cm –1 represent C–O–C groups, which are related to cellulose aliphatic ethers. 31 − 33 …”

“…Furthermore, the peaks at 873 and 809 cm –1 correspond to the aromatic CH bands. Lastly, the peaks between 1050 and 1093 cm –1 represent C–O–C groups, which are related to cellulose aliphatic ethers. − …”