Robert Carleer

The study comprises an in-depth characterization of compositional groups of the liquid by-products obtained from the pyrolysis of swine manure at 500 °C, with the aim of providing an alternative and efficient approach for the valorisation of this waste stream, alongside with the production of biogas and char, the latter of which can be further converted into activated carbon. Two samples were considered: de-watered cake and solid product from anaerobic digestion of swine manure. Biocrude oils were fractionated into weak acidic, strong acidic, alkaline and neutral oil fractions. Subsequently, the neutral oil fraction was separated into paraffinic–naphthenic, slightly polar and polar fractions. All fractions were analyzed by GC–MS. The major identified compositional groups were: (i) for de-watered cake: steroids (40.7%), fatty acids, FAs (23.7%) and n-alkenes/n-alkanes (23.3%); (ii) for solid product from anaerobic digestion: FAs (31.0%), phenols/methoxy phenols (26.6%), n-alkenes/n-alkanes (10.8%) and steroids (10.6%). A variety of short-chain FAs (i.e., linear saturated, mono- and di-unsaturated, cis (i-), trans (ai-), isoprenoid, phenyl alkanoic, amongst others) and methyl esters (FAMEs) were identified as well. FA distribution, nC₁₂–nC₂₀, was similar for both manures studied with nC₁₆ and nC₁₈ as major compounds. FAMEs (nC₁₄–nC₂₈, with even carbon number dominance) in the slightly polar fraction of both samples were accompanied by considerable amounts of oleic (nC_18:1) and linoleic (nC_18:2) acids, and corresponding methyl esters. Hydrocarbons, i.e., n-alkenes/n-alkanes, were in the range of nC₁₅–nC₃₄, with nC₁₈ maximizing. Anaerobically digested manure has resulted in (i) an increase in the portion of longer homologues of hydrocarbons and FAMEs and (ii) the appearance of new FAs series of long chain members nC_22:1–nC_26:1, ω-9. The comprehensive analysis of the biocrude oils obtained from the slow pyrolysis of swine manure indicates their potential for use as biodiesel additives or as feedstock to produce value-added materials.

This study introduces a novel, non-invasive X-ray absorption analysis (XRA) method to evaluate the photonic absorption process of granular activated carbon (GAC) in hospital water purification systems. By leveraging digital radiographic images, this innovative technique monitors the deterioration and oxidation of the GAC filter, predicts its remaining lifetime, and estimates its water dechlorinating capacity. Analyzing the entire GAC filter and making a reuse possible, the new XRA method provides valuable insights into the filter’s condition, enhancing water purification efficiency and costs without analyzing subsamples. Complementary analytical techniques on subsamples, taken at various depths, did not yield valuable additional information of the GAC filter exhaustion condition, nor additionally make a reuse impossible.

A commercial activated carbon (AC) was modified through iron oxide incorporation to obtain microwave absorbers (MWAs) for microwave-assisted pyrolysis. The influence of iron oxide content (5 and 20 wt% Fe₃O₄) and the modification methods were tested as follows: (1) in situ co-precipitation + washing step with Milli-Q; (2) in situ co-precipitation + washing step with Milli-Q/ethanol; and (3) physical iron oxide blending. The resulting MWAs were evaluated on the microwave-assisted pyrolysis of hardwood in a Milestone Flexiwave microwave reactor. The biochar yield varied from 24 wt% to 89 wt% and was influenced by the modification method rather than the iron oxide addition. The MWAs with physically blended iron oxide resulted in biochar yields comparable to conventional biochar (450 °C). Furthermore, the addition of iron oxide-activated carbon composites during the microwave-assisted pyrolysis caused a significant decrease in the biochar’s 16 EPA polycyclic aromatic hydrocarbons, mainly by reducing the amount of pyrene in the biochar.

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic‐inorganic) TiO₂ nanoparticles is important when forming porous hybrid organic‐inorganic metal phosphonates. In the present work, a method was utilized to control the in‐situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic‐inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO₂ nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO₂ nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker‐TiO₂ bonding was altered. Upon subsequent drying of the colloidal TiO₂ solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker‐TiO₂ nanoparticle surface dynamics is crucial for making hybrid organic‐inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.

The chemical regeneration of exhausted granular activated carbon (GAC) from a water treatment plant to produce dialysis water used in hemodialysis treatments for chronic renal disease patients from a general Hospital of Ciego de Avila province, Cuba, was investigated. Activated carbon (AC) exhausted mainly by inorganics (Ca (Ca-chelates), Mg and Na) was regenerated using hydrochloric acid and acetic acid (one regeneration cycle). Solutions of 5%, 10%, 15% and 20%(v/v) as well as four contact times (2 h, 4 h, 6 h and 48 h) for hydrochloric acid and three contact times (2 h, 4 h and 6 h) for acetic acid at 25°C and 1 atm in a dosage of 1 g GAC/10 mL were used. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), thermogravimetric analysis (TGA), X-ray absorption technique (XRA) and Scanning Electronic Microscopy (SEM) were used to evaluate the effect of the regeneration on exhausted GAC. Batch and scaled column experiments were developed. Breakthrough curves were obtained to assess the AC’s performances after chemical regeneration. The removal/adsorption capacity towards free chlorine (as disinfection agent) and hardness ions (expressed in mg CaCO3/L) was estimated using the area under the breakthrough curves from scaled columns experiments. The hydrochloric acid arises as the best acidic regenerator; using a concentration of 20%(v/v), regenerated GACs using hydrochloric acid showed the highest desorption rate of inorganics as well as a free chlorine removal performance of around 30% concerning the virgin GAC sample. A new GAC management scheme is proposed for GACs used in the medical industry to improve the sustainability and economics of the water treatment process.

Green roofs contribute to more sustainable cities, but current commercial substrates suffer from important limitations. If carefully selected, biochar could serve as a viable option for a more sustainable green roof substrate. We propose a protocol to select an optimal biochar for green roof substrate amendment. Coffee husks, medium-density fiberboard, palm date fronds, and a mixture of waste wood, tree bark, and olive stone kernels are selected as residues for biochar production to develop a selection protocol. The residues are pyrolyzed at 350, 450, 500, and 550 °C in a lab-scale reactor. A pyrolysis temperature of 450 °C is selected for upscaling and is based on biochar yield, pH, salinity, and elemental composition. From evaluating the biochar characteristics after upscaling, it can be concluded that the biochar’s carbonization degree is mainly controlled by pyrolysis temperature, while yield, pH, and salinity are more dependent on the biomass properties. Ultimately, our procedure evaluates the presence of important contaminants, the biochar’s water holding capacity, salinity, pH, and carbonization degree. To validate the developed protocol, plant coverage experiments on green roofs are performed, which are quantified using a novel digital image processing method, demonstrating its efficient use to facilitate future biochar selection in substrates.

A mathematical tool has been developed to evaluate the economic advantages of in-situ chemical regeneration of fixed-bed industrial adsorbers of granular activated carbon for cooling water treatment systems in Cuban power plants. Two scenarios of activated carbon (AC) management in a power plant were compared by applying the proposed model. The economic profit by implementing the regeneration strategy as a function of the number of regeneration cycles was determined and optimized. Breakthrough curves were obtained to assess the adsorption performance of the AC after progressive saturation–chemical regeneration cycles using synthetic water and hydrochloric acid, respectively. For the first saturation cycle, the breakthrough time was 272 min and after 10 cycles, it was reduced to 58 min, indicating a decrease of the adsorption capacity of 21%. The AC adsorption performance in terms of saturation time as a function of the number of regeneration cycles was considered one of the tool parameters. The proposed tool allows to determine the optimal number of regeneration cycles for a maximum economic profit in the regeneration strategy. It was demonstrated, using the proposed tool, that after an optimum of seven regeneration cycles, the power plant expends only 26% of the total investment. The simplicity of the tool permits a rapid way to find the most profitable number of regeneration cycles by combining economic, technical and adsorption efficiency parameters in one function, thus improving the AC management strategy at an industrial scale with corresponding environmental and economic advantages, including sustainability.

Fe-TiO₂/AC and Co-TiO₂/AC composites were prepared from activated carbon (AC) derived from residues of peanut hulls and TiO₂ photocatalyst, electrochemically prepared from titanium scrap, and doped with Fe and Co, respectively. The adsorption capacity and photocatalytic activity of the Fe-TiO₂/AC and Co-TiO₂/AC composites were studied for removing and degrading Cibacron Yellow F-4G (CYF-4G) from wastewater. Doped ACs were characterized by thermogravimetry (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), a new X-ray absorption technique (XRA), and elemental analysis (EA). Interesting relationships were found between SEM, XRA, and TGA data and the doped amount of catalyst on ACs. Optimal dye adsorption was found at a pH of 2.0. The CYF-4G adsorption kinetics are followed according to the pseudo-second order model. The experimental data revealed that the Langmuir model fits better than the Freundlich and Temkin models. A decrease in adsorption capacity was observed when the catalyst dope percentage increased. A removal and degradation efficiency of the dye close to 100% was achieved around 120 min. A synergistic adsorption and photocatalytic degradation effect of the Fe-TiO₂/AC and Co-TiO₂/AC composites could be observed when adsorption experiments were conducted under simulated visible radiation.