Biochar-graphene oxide composite is efficient to adsorb and deliver copper and zinc in tropical soil

Abstract

Highly weathered soils have low micronutrient availability and very low efficiency for most soluble fertilizers. In this article the effect of poultry litter biochar-graphene oxide composite (PLB-GO) as a novel adsorbent for copper (Cu) and zinc (Zn) was evaluated, as well as its fertilizing effects on plant growth, nutrient use efficiency and soil fertility. In order to do so, poultry litter biochar (PLB) and PLB-GO were produced, characterized and evaluated by isotherm adsorption and kinetics studies regarding their Cu and Zn sorption and desorption properties. Cu and Zn loaded on PLB and PLB-GO as biochar-based fertilizers (BBF) were also evaluated. PLB-GO showed 16.2% and 17.7% higher Cu and Zn adsorption capacity, respectively, than pristine PLB, and in both cases <0.5% of the sorbed metal content was released in water. Plant effects on growth and nutrient uptake were, in general, higher or similar to the results obtained for sulfates. The application of PLB increased Cu availability while PLB-GO increased Zn availability after cultivation, even after increasing nutrient uptake and being little soluble in water. Addition of small amounts (≤0.5%) of GO in biochar has potential to increase its properties to retain micronutrients and enhance the fertilizer use effectiveness in highly weathered soils.