Adsorptive and kinetic characterization of aqueous zinc removal by biochars


Sergio Mireles, Yongsik Ok, Chu-Lin Cheng


Jihoon Kang, Adsorptive and kinetic characterization of aqueous zinc removal by biochars(2016)SDRP Journal of Earth Sciences & Environmental Studies 1(3)


In many urban areas, stormwater runoff is often contaminated with zinc (Zn) as it washes through galvanized surfaces in buildings and tire dusts from pavements. Biochars have shown a great potential to treat stormwater runoff contaminated with heavy metals due to their favorable physical and chemical characteristics. Biochar materials produced from pyrolysis of oak tree and wood at 400°C and 450 °C, respectively, were studied to characterize adsorption behaviors of Zn from aqueous solution to assess their applicability as a filter media for stormwater treatment. Two adsorption isotherm models, Freundlich and Langmuir, were fitted to the batch-scale experimental data. The kinetics of Zn adsorption was investigated under two contrasting physical condition (stagnant vs. agitated). The adsorption isotherm was better fitted with the Langmuir model (R2 = 0.99) than the Freundlich model (R2 = 0.62-0.72). Oak tree biochar (~ 21,400 mg kg-1) outperformed wood biochar (~ 6,100 mg kg-1) in the Zn adsorption due to higher molar ratio of oxygen to carbon in the oak tree biochar. The Zn adsorption by the biochars were less effective under stagnant condition, suggesting that external energy for agitation is needed when considering biochar as a stormwater filter media. Overall the kinetics data of Zn adsorption fitted well with the pseudo-second order model (R2 = 0.99), indicating that chemisorption was dominant mechanism for the Zn adsorption onto the biochars. This study highlights a potential for biochar to be an effective adsorbent to remove Zn with relatively short contact time for stormwater and industrial applications.

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