Effects of Corn Cob Produced Biochars on Urea Recovery from Human Urine and Their Application as Soil Conditioners

Abstract

The sorption of urea to biochars produced by pyrolysis of corn cob (CC) with different pyrolytic temperatures was investigated to understand its related sorption mechanisms. Biochar samples were studied by elemental analysis, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy, and Fourier transform IR spectroscopy. Batch sorption experiments revealed that the Freundlich isotherm model (R2 = 0.999) fitted better with the sorption process than the Langmuir and Dubinin–Radushkevich isotherm models. Furthermore, the sorption mechanisms of biochars derived from CC changed from adsorption‐dominant at low pyrolysis temperatures (300 and 400°C) to partitioning‐dominant at higher pyrolysis temperatures (500 and 600°C). Column study indicated that CC‐300 has the highest urea sorption capacity with 20.9 mg g−1 followed by CC‐400, CC‐500, and CC‐600. A germination test was also conducted and the results showed that the exhausted biochar positively influenced the plant growth and can be potentially used as soil conditioner.