Characterisation of Activated Carbons Obtained from Rice Husk

Activated Carbon/Pectin Composite Enterosorbent for Human Protection from Intoxication with Xenobiotics Pb(II) and Sodium Diclofenac

The use of enterosorbents—materials which can be administered orally and eliminate toxic substances from the gastrointestinal tract (GIT) by sorption—offers an attractive complementary protection of humans against acute and chronic poisoning. In this study, we report the results of developing a microgranulated binary biomedical preparation for oral use. It was designed with a core-shell structure based on pectin with low degree of esterification as the core, and nanoporous activated carbon produced from rice husk, AC-RH, as the shell, designated as AC-RH@pectin. The adsorption properties of the synthesized materials were studied in aqueous solutions for the removal of lead (II) nitrate as a representative of toxic polyvalent metals and sodium diclofenac as an example of a medicinal drug. The composite enterosorbent demonstrated high adsorption capacity for both adsorbates studied. Adsorption kinetics of lead and diclofenac adsorption by AC-RH, pectin, and AC-RH@pectin, fitted well a pseudo-second-order model. According to the Langmuir adsorption isotherm model, the best fitted isotherm model, the maximum adsorption capacity, q_max, of AC-RH@pectin for diclofenac and for lead (II) was 130.9 mg/g and 227.8 mg/g, respectively. Although q_max of AC-RH for diclofenac, 537.6 mg/g, and q_max of pectin for lead (II), 245.7 mg/g, were higher, the maximum adsorption capacity of AC-RH for lead (II), 52.7 mg/g, was much lower than that of the composite AC-RH@pectin and the adsorption capacity of pectin for diclofenac was negligible. Therefore, the composite material AC-RH@pectin demonstrated substantial efficiency of removing both species which potentially defines it as a more universal enterosorbent suitable for treating poisoning caused by substances of different chemical nature.

Synthesis and Electrochemical Behavior of the Molybdenum- Modified Electrode Based on Rice Husk

The article presents the results of electrochemical studies made on carbon paste electrode based on bisorbents powder modified by molybdenum. Bisorbent consists of carbon and SiO2. It was synthesized as a support structure obtained from rice husk thermal decomposition products. The obtained sorption material has surface with high specific area – 200 m2/g. Bisorbent was further modified by (NH4)6Mo7O24 · 4H2O (10 wt.%). The elemental composition of used RH was also determined. The surface morphology of plain and modified BS samples was studied. Recording of voltammetric curves was carried out at рН = 3.80, рН = 6.40 in 0.2 М electrolyte solution of Li2SO4. Cathodic and anodic waves were obtained which related to oxidation and reduction processes of molebdenium compounds in the entire range of the potentials (0.8 ÷ -1.2 V). The range of changing molybdate ions concentrations in solution was 2·10‒4 ÷ 10‒2 M. The dependencies of kinetic and electrochemical parameters on paramolybdate ions concentration were studied for modified electrode. Nature of changes in molybdenum reduction currents and oxidation currents indicates that Mo+6 reduction may occur by different mechanisms depending on the composite electrode properties. Results showed the possibility of further the synthesized composite system use for voltammetric determination of low (10‒4–10‒2) concentrations of ions in a solution.