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Abstract:The present work investigates arsenic, antimony and tellurium sorption using iron modified peat. The results were obtained using batch tests and the sorption was studied as a function of initial metalloid concentration, pH and sorption time, as well as the presence of competing substances. The obtained results indicate that modification of peat with Fe compounds significantly enhances the sorption capacity of the sorbents used for sorption of arsenic, antimony and tellurium. The optimal pH interval for the sorption of Sb(III) is 6.5-9 and for As(V) and Sb(V) -3-6, while As(III) and tellurium sorption using Fe-modified peat is favourable in a wider interval of 3-9. The presence of competing ions as well as HA affect sorption of metalloids on Fe-modified peat. A minor impact on the reduction of metalloid sorption was detected in the presence of nitrate, sulphate, carbonate and tartrate ions, while in the presence of phosphate and HA the sorption ability of metalloids can be considerably reduced. The obtained results of kinetic experiments indicate that sorption of metalloids on Fe-modified peat mainly occurs relying on mechanisms of physical sorption processes.Keywords: peat, sorbents, arsenic, antimony, tellurium, metalloids Environmental contextGrowing attention is being paid to environmental pollution with metalloids (As, Sb, Te) requiring new approaches for removal of these elements from water. The present work investigates arsenic, antimony and tellurium sorption using iron modified peat. Iron modified peat has high sorption capacity in respect to all environmentally relevant metalloid speciation forms [As(V), As(III), As(org.), Sb(III), Sb(V), Te(IV) and Te(VI)]. The sorption takes place according to mechanisms of physical sorption and is affected by pH of a solution as well as competing ions.

In this study, new composite materials of montmorillonite, biochar, or aerosil, containing metal–organic frameworks (MOF) were synthesized in situ. Overall, three different MOFs—CuBTC, UTSA-16, and UiO-66-BTEC—were used. Obtained adsorbents were characterized using powder X-ray diffraction, thermogravimetric analysis, nitrogen adsorption porosimetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrophotometry. Additionally, the content of metallic and nonmetallic elements was determined to investigate the crystalline structure, surface morphology, thermal stability of the obtained MOF-composites, etc. Cyclic CO2 adsorption analysis was performed using the thermogravimetric approach, modeling adsorption from flue gasses. In our study, the addition of aerosil to CuBTC (CuBTC-A-15) enhanced the sorbed CO2 amount by 90.2% and the addition of biochar (CuBTC-BC-5) increased adsorbed the CO2 amount by 75.5% in comparison to pristine CuBTC obtained in this study. Moreover, the addition of montmorillonite (CuBTC-Mt-15) increased the adsorbed amount of CO2 by 27%. CuBTC-A-15 and CuBTC-BC-5 are considered to be the most perspective adsorbents, capturing 3.7 mmol/g CO2 and showing good stability after 20 adsorption-desorption cycles.

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