Grapefruit Peel Biochar Applications for Immobilizing Copper and Lead in Soil

MICHAEL Alfredo NAVARRO, The University of Texas Rio Grande Valley

Copyright 2023 The Author. All Rights Reserved.

Abstract

This study investigated the efficacy of grapefruit peel (GP) derived biochar materials (two pyrolysis temperatures 450°C and 800°C) as a potential adsorbent to immobilize heavy metal (copper and lead) in a local sandy loam clay soil. A batch adsorption test with heavy metal concentrations at 50 mg L-1, and 100 mg L-1 revealed that soil itself had the highest immobilization percentage compared to the GP biochars. A soil column experiment was conducted to determine how much the GP biochar samples and the tested soil will exhibit adsorptive characteristics for heavy metals when 50 ml of 50 mg L-1 copper or lead is loaded into the columns for 10 adsorption days followed by 10 desorption (50 ml of De-Ionized water) days. The columns that contained a GP biochar were added with either a 5%(w/w), or 10%(w/w) amendment rates, soil: biochar. The results of the column experiment exhibited that all columns had a 99% lead and copper retention/ immobilization percentage of heavy metals. The last experiment was the radish seed germination test, in which radish seeds were applied and monitored over 21 days with spent soil columns. This was carried out to examine how heavy metal loaded soil columns with and without biochar would affect germination and biomass(g) production. The soil columns amended with GP biochar at a 10%(w/w) allowed for the radish seeds to germinate twice as fast than the control, and on average contained more biomass. Study results indicated that GP biochar can be considered as a potential soil additive that can participate in the immobilization of copper and lead in a local soil while it can improve vegetation establishment in the treated soil.