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Title: Engineered carbon (biochar) prepared by direct pyrolysis of Mg-accumulated tomato tissues: Characterization and phosphate removal potential

Author
item YING, YAO - University Of Florida
item BIN, GAO - University Of Florida
item JIANJUN, CHEN - Mid Florida Research & Education Center
item TIE, WANG - University Of Florida
item MING, ZHANG - University Of Florida
item MANDU, INYANG - University Of Florida
item YUNCONG, LI - University Of Florida
item Alva, Ashok

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2013
Publication Date: 3/19/2013
Citation: Ying, Y., Bin, G., Jianjun, C., Tie, W., Ming, Z., Mandu, I., Yuncong, L., Alva, A.K. 2013. Engineered carbon (biochar) prepared by direct pyrolysis of Mg-accumulated tomato tissues: Characterization and phosphate removal potential. Bioresource Technology. 138:8-13.

Interpretive Summary: Biochar is carbon rich by product of production of bio energy from biomass using a process called pyrolysis. In this study magnesium (Mg) enriched tomato leaves were used in pyrolysis which resulted in by product biochar that was an excellent sorbing material to remove phosphate from aqueous solution. These biochar contained nanoscale Mg(OH)2 and MgO particles on carbon surface, which inturn were responsible for greater sorption of phosphate unlike the other biochars without these nanoparticles. This study revealed the mechanism for increased phosphate sorption by this biochar. The phosphate sorbed by this biochar was bioavailable as evident from it's extraction by Mehlich-3 extractant as well as P uptake by grass seedlings. An efficient P sorption material is of interest to use for removal of P from wastewater. The distinct advantage of using biochar to remove P is that it can be reused as a soil amendment to supply P slowly over the crop growing period.

Technical Abstract: An innovative synthesis was developed to produce engineered biochar from magnesium (Mg) enriched tomato tissues through slow pyrolysis in a N2 environment. The resulting Mg-biochar composites showed excellent sorption ability to phosphate in aqueous solutions. The engineered biochar contained nanoscale Mg(OH)2 and MgO particles on carbon surface within its pore structures. Those nanoparticles are the dominant factor governing the removal of aqueous phosphate by the engineered biochar. Results from batch sorption experiments suggested that although sorption of phosphate (P) to the biochar was controlled by relatively slow kinetics, the maximum sorption capacity of phosphate to the biochar could reach >100 mg/g. Post-sorption characterization results indicated that P sorption by the engineered biochar was mainly controlled by two mechanisms: precipitation of phosphate through chemical reaction with Mg particles and surface deposition of phosphate onto Mg crystals on biochar surface. Most of the P retained in the biochar through surface deposition was bioavailable, which was confirmed by the Mehlich 3 test. Desorption experiment indicated that P retained by this biochar was released equally at multiple successive extractions. In addition, the P-laden biochar significantly stimulated grass seed germination and growth. These results suggested the spent P-laden biochar can be applied directly to soils as a slow-release fertilizer. Keywords: engineered carbon, biochar, nanocomposites, phosphate, slow-release fertilizer