Synthesis of Magneto-Susceptible Adsorbents on the Basis of Hydrolytic Lignin Using Iron(III) Oxide
Adsorption methods are one of the most common ways of chemical separation. The introduction of adsorption separation technologies is constrained by a number of factors. The use of powder adsorbents, which possess magnetic properties, will allow intensifying the processes of adsorption and separation of the adsorbent from the phase to be purified. The modern methods for synthesizing magneto-susceptible adsorbents are mostly multi-stage, complex and expensive. The goal of research is to develop a simple and inexpensive way for their synthesis by pyrolysis using hydrolytic lignin as a carbon-containing raw material, which is the large-scale waste of hydrolysis plants, and iron(III) oxide as an activating agent and source of magnetic forms of iron. Synthesis of adsorbents is carried out by the method of a planned experiment. The influence of the synthesis conditions (the iron(III) oxide content in the initial mixture, the temperature and duration of pyrolysis) on the properties of the obtained MSA is studied. The adsorption activity of the adsorbents is measured by methylene blue (MB) and iodine, the relative magnetic susceptibility (RMS) and the parameters of the porous structure of adsorbents (the total volume of sorbing pores, the volume of micro- and mesopores) are determined. The porous structure is studied by the method of lowtemperature nitrogen adsorption. According to the adsorption parameters, the obtained MSA are superior to the closest analogues. The maximum adsorption activity of MB is 316 mg/g, which is almost 1.5 times higher than GOST 4453-74 requirements for OУ-Б clarifying carbon; the maximum adsorption activity of iodine is 1290 mg/g, which is 2 times higher than the GOST 6217-74 requirements for БАУ-А active carbon. The relative magnetic susceptibility is on average 2 times higher than that of magnetite; the maximum volume of sorption, micro- and mesopores is 0.200, 0.076 and 0.113 cm<sup>3</sup>/g, respectively. The adsorbents synthesized by the proposed method demonstrate good adsorption and magnetic properties and can be applied in science and technology. In addition, the industrial production of MSA on the basis of hydrolytic lignin will increase the profitability of hydrolysis industries by producing a valuable product and to some extent solve the problem of utilization of lignin dumps.