Abstract
In this paper, rice straw was pyrolyzed at three temperatures (400, 500 and 600 degrees C) to study its influence on biochars properties and its chemical composition as soil amendment. Elemental analysis, surface area, pore size distributions, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) were used in the characterization of resultant biochar. As pyrolysis temperature increased, ash content, yield, acidity, total hydrogen and oxygen contents decreased while total carbon, nitrogen and basicity decreased by the reason of pyrolytic volatilization through pyrolysis. Surface area, total pore, micropore and mesopore volume reach its maximum at pyrolysis temperature of 500 degrees C in biochar-500. Biochars exhibit wide particle size distribution, from narrow micropores (<0.7 nm) to wide mesopores (>2.0 nm). One sharp peaks was obtained at about 1.0-1.5 nm in the case of micropore region and two broad peaks at about 3.0 and 5.0 nm in mesopore region. FTIR spectra exhibited that high pyrolysis temperatures induce condensation reactions, which leads to aromaticity increasing and decreasing of biochar polarity. With increasing of pyrolysis temperature, cellulose loss and minerals contents increased, as showed by XRD analysis. Results recommend that high pyrolysis temperature give biochar with higher carbon sequestration potential characteristics when applied as soil amendment. Rice-based biochars gave high adsorption capacity for various molecular sizes like phenol, iodine and methylene blue. Biochars acidity/alkalinity and hydrophilicity represents one of the most important property that affecting their solution adsorption behavior.