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Iron-modified biochar derived from rice straw for aqueous phosphate removal
Author(s)
Thawornchaisit, Usarat
Donnok, Korawan
Samphoanoi, Natchaphat
Pholsil, Pimwimon
Date Issued
January 1, 2019
Type
Article
Abstract
Conversion of rice straw to biochar, followed by chemical modification of the biochar with iron salts under alkaline conditions can turn agricultural biomass waste into a useful adsorbent material for phosphorus removal. Study of the rice straw-to-biochar conversion process at various pyrolysis temperatures showed that biochar yield decreased with increased pyrolysis temperature: The yield of stable organic matter and specific surface area was found to be optimum at 400°C. An Fe coating process, through direct precipitation of FeCl3. 6H2O or co-precipitation of FeCl3. 6H2O and FeSO4. 7H2O on biochar, led to Fe-modified rice straw biochars. Based on physical appearance, SEM, FT-IR and XRF, we confirmed that Fe was well retained in the biochar. The pHpzc was approximately 7. 6 and 8. 0 for Fe(III) + Fe(II)-modified biochar and Fe(III) modified biochar. Therefore, the modified biochar could attract negatively charged phosphate species in a system, like natural water or domestic wastewater, where pH is normally less than their pHpzc. In laboratory batch adsorption tests, phosphate removal efficiency was enhanced, rising from about 35.4% in the unmodified biochar to 69.5% in Fe(III)+Fe(II)-modified biochar and 83.0% in Fe(III) modified biochar.
Citation
Current Applied Science and Technology, 19(3), 263-275, 2019