Biochar functionalized with layered double hydroxides improve physicochemical properties of growing media

Abstract

Despite their extensive use in wastewater treatment, biochar/layered double hydroxides (BC/LDHs) may serve as novel growing media (GM) amendments for horticultural farming. In the present study, GM was supplemented with BC/LDHs at three application rates [0%, 2.5%, and 5.0% (wt/wt)] denoted as BC/LDHs0, BC/LDHs2.5, and BC/LDHs5.0, respectively, and successive changes in the physiochemical properties of GM were evaluated. The experimental results indicated that at the end of the incubation period, GM was vastly stimulated after BC/LDH amendments, particularly in the case of BC/LDHs5.0, where the pH (7.05) and electrical conductivity (0.43 dS/m) were in accordance with the optimal criteria for soilless cultivation. Moisture content, bulk density, total porosity, and water retention were also improved after BC/LDH remediation although there were insignificant differences among individual dosages for the last two indices. Although increased amendment levels did not benefit total carbon and nitrogen, the maximum efficiency that was reflected in an enhancement of at least 86% in phosphorus, magnesium, and aluminum contents was derived from BC/LDHs5.0. Nevertheless, due to an overriding concern over aluminum interference, BC/LDHs2.5 was recommended given its non-significant difference with non-amendment. Such positive effects of BC/LDHs, on a wide range of GM quality indicators, signify their potential in amendment applications. This study not only provides an alternative approach for the reuse of plant-essential nutrients, but also a means to facilitate sustainable adsorbent waste management, through the extended applicability and validity of BC/LDHs and their utilization in agricultural systems.