Rice husk biochar: production and sorption properties

Rice husk processing is not only a global problem, but also an acute one in Ukraine - utilization and processing of rice husks into a targeted secondary product is an urgent and promising task, given the volume of their accumulation. The purpose of this study is to obtain biochar that can be used efficiently and effectively in the anaerobic digestion process for biogas production and to determine its sorption characteristics. The results of determining the chemical composition of raw materials and biochar obtained by pyrolysis and microwave irradiation, with an increase in the pyrolysis temperature, the proportion of lignin and ash increases. Studies of the interaction of lead ions with plant material and its modified forms show that sorption by modified forms is much higher than by plant material, probably due to differences in chemical composition, surface properties, etc. Comparison of the data on the sorption of lead ions by modified forms (biochar) allows us to conclude that the method of preparation has a significant effect on the sorption value. The pyrolysis temperature of biochar has a favorable effect on the sorption properties of the samples. The obtained adsorption isotherms belong to the L-type. The maximum sorption values are observed under the experimental conditions at an initial concentration of lead ions of 1.00 mg/ml. The study of the kinetic parameters of the processes of lead ion sorption by biochar preparations based on the curve of residual lead ion concentrations shows that equilibrium in the system is achieved in a few hours. The rate of lead ion sorption increases with increasing pyrolysis temperature. The highest rate of lead ion sorption is observed for biochar obtained by using microwave irradiation. The maximum sorption values are observed after 2.5...3 hours of incubation. The value of lead ion sorption by Biochar-300 is 40.7 % after 3 hours of their joint incubation. An increase in the interaction time does not lead to a significant increase in the degree of sorption of lead ions by plant material and its modified forms.