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CaO-based looping cycles are promising processes for CO2 capture from both syngas and flue gas. The technology is based on cyclical carbonation of CaO and regeneration of CaCO3 in a dual fluidized-bed reactor to produce a pure CO2 stream suitable for sequestration. The main limitation of natural sorbents is the loss of carrying capacity with increasing number of reaction cycles, resulting in the need for extra sorbent, and subsequent spent sorbent waste. Use of spent sorbent from CO2 looping cycles for SO2 capture is investigated in this study. Three limestones were investigated: Kelly Rock (Canada), La Blanca (Spain), and Katowice (Poland, Upper Silesia). Carbonation/calcination cycles were performed in a tube furnace with both the original limestones and samples thermally pretreated for different times (i.e., sintered). The spent sorbent samples were sulfated in a thermogravimetric analyzer (TGA). The changes in the resulting sorbent pore structure were then investigated using mercury porosimetry. It has been shown that the sulfation rates of both thermally pretreated and spent sorbent samples are lower in comparison with those of the original samples. However, final conversions of both spent and pretreated sorbents after longer sulfation time were comparable or higher than those observed for the original sorbents under comparable conditions. Maximum sulfation levels strongly depend on sorbent porosity and pore surface area. The shrinkage of sorbent particles during calcination/carbonation cycling resulted in a loss of sorbent porosity on the order of ≤48%, which corresponds to maximum sulfation levels of ∼55% for spent Kelly Rock and Katowice. This is ∼10% higher than that seen with the original samples after 15 h of sulfation. By contrast, La Blanca limestone had more pronounced particle shrinkage during pretreatment and cycling, leading to porosities lower than 35%, which resulted in sulfation conversion of spent samples <30%, which is significantly lower than that for the original sample (45%). These results showed that spent sorbent samples from CO2 looping cycles can be used as sorbents for SO2 retention in cases where significant porosity loss does not occur during CO2 reaction cycles. The higher conversions of spent samples are explained by a shift in pore size distribution toward larger pores that reduce the reaction rate and pore plugging near the particle’s outer surface, with formation of either unreacted core or unreacted network patterns. In the case of spent Kelly Rock and Katowice samples, sorbent particles are practically uniformly sulfated, achieving final conversions that are determined by the total pore volume available for the bulky CaSO4 product.

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Locally available apricot (Prunus armeniaca L.) shells classified as a waste product from fruit processing, were alkali activated in order to develop an efficient heavy metal ions sorbent for water purification. To examine the changes occurred after alkali treatment, raw (SH) and modified apricot shells (SHM) were thoroughly characterized in terms of their chemical composition and surface properties. Chemical analysis revealed that alkaline treatment causes the disintegration of hemicellulose (its content decreased from 19.2 to 3.5 %), which was in accordance with FTIR results. SEM micrographs and the mercury intrusion porosimetry revealed a larger surface area and porosity of SHM. Bohem's acid-base titration method indicated that the most of the SHM surface carboxylic groups were in sodium salt form and together with the pH of points of zero charge showed increase of surface alkalinity after modification. Treatment with NaOH enhanced the adsorption capacity by 154, 61 and 90 % for Cu 2+ , Zn 2+ and Pb 2+ , respectively. The amount of cations released from SHM was almost equal to the amount of adsorbed metal ions, suggesting ion exchange mechanism. The pseudo-second order kinetic indicated that the heavy metals cations were bound predominantly by complexation. In order to establish the effectiveness of the biosorbent in real wastewater sample, SHM was employed for cleaning-up of drain water emanating from atomic adsorption spectrophotometer. The SHM showed high removal efficiency towards multiple metal ions. The amounts of Fe, Pb, Cu and Cr ions were reduced by 97, 87, 81 and 80 %, respectively, while Ni and Zn amounts were reduced for 33 and 14 %. Used biosorbent SHM can be successfully regenerated with HCl (desorption > 95 %) and after regeneration biosorbent can be reused or it can be safely disposed.

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TiO 2 powders with different specific surface area were prepared using reproducible, sol-gel synthetic route and their ability to form hybrids with catechol and 5-amino salicylic acid was compared with the commercially available Degussa P25 TiO 2 powder. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption-desorption isotherms indicated that TiO 2 samples cover reasonably wide size and/or specific surface area range (50-115 m 2 /g). The surface modification of TiO 2 powders with catechol and 5-amino salicylic acid induced significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of TiO 2 in powder form have never been reported in the literature. The largest red M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 2 shift of the absorption onset was observed for sample with the largest specific surface area upon surface modification with both ligands. The binding of the modifier molecules to the surface Ti atoms was studied using Fourier transform infrared spectroscopy.

The synthetic procedures for preparation of free-standing and attached to polymer support surface-modified TiO2 nanoparticles (NPs) with absorption extended into the visible spectral region due to charge transfer complex formation were developed. The one-step synthesis of colloids consisting of surface-modified TiO2 NPs is based on the reaction between titanium­(IV) isopropoxide (TTIP) and lauryl galatte in nonprotic organic solvents (tetrahydrofuran, xylol, chloroform). The poly­(GMA-co-EGDMA) copolymer decorated with surface-modified TiO2 NPs was obtained in two steps. First, copolymer was functionalized with dopamine and then treated with TTIP in organic solvent at slightly elevated temperature. Thorough microstructural and optical characterization of free-standing and attached to polymer support surface-modified TiO2 NPs was performed involving transmission electron microscopy as well as absorption and reflection spectroscopy. Infrared spectroscopy was used to understand coordination of ligands to surface Ti atoms. Photoredox chemistry of surface-modified TiO2 NPs attached to the polymer support was tested. Enhanced photooxidative ability of composite was demonstrated by degradation of organic dye crystal violet under visible light illumination, i.e., using photons with energy smaller than 2.75 eV. On the other hand, photocatalytic hydrogen production was used to demonstrate photoreduction ability of surface-modified TiO2 NPs attached to the polymer support.