Buckwheat husk biochar: Preparation and study of acid-base and ion-exchange properties

Abstract

Ukraine is one of the world's leading producers of buckwheat grain, so it is very important to address the issue of including its processing waste in the production cycle. Buckwheat husk is a promising raw material for biochar production. The aim of the study is to obtain biochar as an additive during food waste composting and to characterise its acid-base and ion-exchange properties. The nature of the potentiometric titration curves of biochar is determined by the additive contribution of all ionised groups of biochar and allows us to classify the studied products as ion exchangers of polyfunctional type. It has been shown that, possessing the properties of ampholytes, biochars in the composting process not only act as acceptors of metal ions, but also function as a soft regulator of pH. The number of groups with the ability to exchange anions ranges from 0.1 (biochar-500) to 1.2 (biochar-MX). The groups with the highest pKa values in the range of biochars studied were found in biochar-500 (pK 7.5), biochar-MX (pK – 7.3) and biochar-300 (pKb 7.0). Other anion-exchange groups have pKb from 4.9 to 6.3 meq/g, which characterises them as weakly basic