Spent tea leaves: A new non-conventional and low-cost biosorbent for ethylene removal

• MSTLP can be used as an efficient, green and cost effective adsorbent for the removal of phytohormone.
• Micro-sized spent tea leaf powder can be easily regenerated.
• The adsorption of ethylene involved in diffusion control process.
• Adsorption capacity and thermodynamic parameters (ΔG°, H° and ΔS°) of MSTLP were identified.

This characterizations of the low-cost microsized spent tea leaf powder (MSTLP) and the effectiveness on its use as biosorbent in the removal of ethylene from a gaseous stream was investigated. Microprocessing treatment of used tea leaves significantly enhanced its ethylene removal capability. The effects of MSTLP dosage, initial ethylene concentration, and temperature on the adsorption of ethylene on MSTLP were evaluated. Moreover, the surface area/pore size distribution, functional group, and morphology of MSTLP samples were characterized. The kinetic adsorption data conformed well to a pseudo-second-order equation, and this adsorption was involved in intraparticle diffusion. The negative value of ΔG0 and the positive value of ΔS0 indicate that the adsorption of ethylene onto MSTLP was a spontaneous process. The adsorption capacity was found to increase with decreasing temperature and increasing MSTLP dosage. The maximum adsorption capacities varied from 0.68 to 6.93 μmol/g at 25 °C based on the fits of Langmuir isotherm. MSTLP could be regenerated, and reused ten times for ethylene adsorption. The results show that a suitable choice of the microprocessing procedure for agriculture byproducts permits production of cheap biosorbent with high sorption capacity of ethylene.