Although liquid products derived from the pyrolysis of biomass are promising for the production of petroleum-like hydrocarbon fuels, the catalytic burden of hydrodeoxygenation must be reduced to achieve feasible upgrading processes. Herein, mild hydrotreating of an acid-rich biomass pyrolysis oil (bio-oil) with an unusually high total acid number (588 mg KOH/g bio-oil) was performed to stabilize the low-quality bio-oil. Ru-added TiO₂-supported transition metal catalysts stabilized the bio-oil by reducing its acidity more compared to what could be achieved by Ru-free catalysts; this process also leads to lower loss of organic compounds compared to when using a Ru/TiO₂ catalyst. Based on the performance of transition metal catalysts, including Ni, Co, and Cu, supported on TiO₂, tungstate-zirconia, or SiO₂, supported bimetallic catalysts were prepared by adding Ru to the TiO₂-supported metal catalysts. The bimetallic catalysts Ru/Ni/TiO₂ and Ru/Co/TiO₂ exhibited good decarboxylation activity for the removal of carboxylic acids and a higher yield of organic compounds compared to that provided by Ru, which can be deemed appropriate for feedstocks when hydrodeoxygenation needs to suppress the loss of organic reactants. Using these catalysts, the carboxylic acid concentration was reduced to 319–323 mg KOH/g bio-oil with organic yields of 62–63 wt% at reaction temperatures 150–170 °C lower than the temperature required for direct conversion of carboxylic acids to alcohols or deoxygenates. The improved catalytic hydrotreating activity of Ru-added transition metals can be attributed to the high acid site densities of these catalysts along with their improved hydrogenation activities.

This study investigated the factors that regulated the degradation of perfluorooctanoic acid (PFOA) in laccase-catalyzed oxidative humification reactions with 1-hydroxybenzotriazole (HBT) as a mediator. The reaction rates were examined under conditions with key factors varied, including initial PFOA concentrations, laccase and HBT dosages, and the ionic contents of the reaction solutions. The PFOA degradation followed pseudo-first order kinetics, and the rate constants (k) were similar for the high (100 μmol L⁻¹) and low (1.00 μmol L⁻¹) initial PFOA concentrations, respectively at 0.0040 day⁻¹ (r² = 0.98) and 0.0042 day⁻¹ (r² = 0.86) under an optimum reaction condition tested in this study. The metal ions contained in the reaction solution appeared to have a strong impact on PFOA degradation. Differential UV-Vis spectrometry revealed that Cu²⁺ can complex with PFOA, which plays an essential role to enable PFOA degradation, probably by bridging the negatively charged PFOA and laccase, so that the free radicals of HBT that are released from laccase can reach and react with PFOA. It was also found that Fe³⁺ plays a similar role as Cu²⁺ to enable PFOA degradation in the laccase-HBT reaction system. In contrast, Mg²⁺ and Mn²⁺ cannot complex with PFOA under the investigated conditions, and do not enable PFOA degradation in the laccase-HBT system. Fluoride and partially fluorinated compounds were detected as PFOA degradation products using ion chromatography and high resolution mass spectrometry. The structures of the products suggest the reaction pathways involving free-radical initiated decarboxylation, rearrangement, and cross-coupling.

Novel copper-nickel ferrite nanocatalyst loaded on multi-walled carbon nanotube (MWCNTs-CuNiFe₂O₄) was synthesized and applied to activate peroxymonosulfate (PMS) in the degradation of the reactive black 5 (RB5). The structure of the catalyst was well characterized by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The MWCNTs-CuNiFe₂O₄/PMS system showed a high performance in the degradation of RB5 with a kinetic rate of 1.5–2.5 times higher than homogeneous and heterogeneous systems. Maximum degradation efficiency (99.60%) was obtained at an initial pH of 7, catalyst dosage of 250 mg/L, PMS dosage of 4 mM, the temperature of 25 °C, and reaction time of 15 min. Anion experiments emphasized that the presence of nitrate, carbonate, and phosphate in the solution reduced the degradation efficiency by producing reactive species with low oxidation potential. The RB5 degradation rate evolved with temperature, and the activation energy was obtained to be 44.48 kJ/mol. The mechanism of PMS activation and production of free radicals was proposed based on tert-butyl alcohol (TBA), ethanol (EtOH), and potassium iodide (KI) scavengers. Trapping experiments showed that both sulfate (SO₄•⁻) and hydroxyl (•OH) radicals are involved in the catalytic degradation of RB5. The effective treatment of real wastewater and tap water by the MWCNTs-CuNiFe₂O₄/PMS system requires a long reaction time. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that RB5 can be degraded via methylation, decarboxylation, hydroxylation, and ring/chain cleavage pathways. The stable catalytic activity after three consecutive cycles suggested that MWCNTs-CuFe₂O₄ is a novel reusability catalyst in PMS activation.

Chlorinated aromatic organic compounds are extremely toxic to the environment and cause cancer to the human body. Pentachlorophenol (PCP) is a hydrophobic and ionic organic compound that is employed as a production material in various industries. Although the Taiwanese government has banned the use of PCP for years, large PCP-contaminated areas remain in Southern Taiwan. Chemical oxidation, which has been proposed as a viable method for restoring PCP-contaminated areas, involves the use of micronanosize birnessite (δ-MnO₂), which is a type of manganese oxide and a natural mineral in soil environments. The goal of this study was to simulate the decontamination of the underlying soil of the PCP-contaminated areas, which is situated in anaerobic and lightless environment. Through the use of a self-developed gas release and absorption reaction flask, the oxidative mineral decarboxylation and dechlorination effects of δ-MnO₂ on PCP in aerobic and anaerobic (with oxygen removed through the use of nitrogen) environments without light were investigated. Results indicated that adding δ-MnO₂ facilitated the oxidative decarboxylation and dechlorination of PCP and the release of Cl⁻ in an aerobic, lightless environment without microbial activity. In the anaerobic environment, the oxidative decarboxylation effect of δ-MnO₂ on PCP decreased significantly, and the dechlorination effect was the primary reaction. Accordingly, adding δ-MnO₂ inorganically destroys aromatic benzene and releases CO₂ and Cl⁻. The molar ratio between CO₂ and Cl⁻ was calculated to assess the mechanisms of the distinct reaction systems. The parameters and data acquired from the experiment, which involved simulating the conditions of the contaminated areas, can be used in planning the on-site management of the PCP contamination; in particular, these parameters and data provide a reference for eliminating PCP from underlying soil—including groundwater-saturated layers.

Non-edible Ceiba oil has the potential to be a sustainable biofuel resource in tropical countries that can replace a portion of today’s fossil fuels. Catalytic deoxygenation of the Ceiba oil (high O/C ratio) was conducted to produce hydrocarbon biofuel (high H/C ratio) over NiO-CaO₅/SiO₂-Al₂O₃ catalyst with aims of high diesel selectivity and catalyst reusability. In the present study, response surface methodology (RSM) technique with Box-Behnken experimental designs (BBD) was used to evaluate and optimize liquid hydrocarbon yield by considering the following deoxygenation parameters: catalyst loading (1–9 wt. %), reaction temperature (300–380 °C) and reaction time (30–180 min). According to the RSM results, the maximum yield for liquid hydrocarbon n-(C₈–C₂₀) was found to be 77% at 340 °C within 105 min and 5 wt. % catalyst loading. In addition, the deoxygenation model showed that the catalyst loading-reaction time interaction has a major impact on the deoxygenation activity. Based on the product analysis, oxygenated species from Ceiba oil were successfully removed in the form of CO₂/CO via decarboxylation/decarbonylation (deCOx) pathways. The NiO-CaO₅/SiO₂-Al₂O₃ catalyst rendered stable reusability for five consecutive runs with liquid hydrocarbon yield within the range of 66–75% with n-(C₁₅ + C₁₇) selectivity of 64–72%. Despite this, coke deposition was observed after several times of catalyst usage, which is due to the high deoxygenation temperature (> 300 °C) that resulted in unfavourable polymerization side reaction.

Advanced oxidation processes (AOPs) using various energy sources and oxidants to produce reactive oxygen species are widely used for the destruction of recalcitrant water contaminants. The current study is about the degradation of two emerging pollutants—salicylic acid (SA) and methyl paraben (MP)—by high-frequency ultrasonication followed by identification of the oxidation byproducts and modeling of the reaction mechanisms using the density functional theory (DFT). The study also encompasses prediction of the aquatic toxicity and potential risk of the identified byproducts to some aquatic organisms bussing the ECOSAR (Ecological Structure Activity Relationships) protocol. It was found that the degradation of both compounds was governed by •OH attack and the pathways consisted of a cascade of reactions. The rate determining steps were decarboxylation (~ 60 kcal mol⁻¹) and bond breakage reactions (~ 80 kcal mol⁻¹), which were triggered by the stability of the reaction byproducts and overcome by the applied reaction conditions. Estimated values of the acute toxicities showed that only few of the byproducts were harmful to aquatic organisms, implying the environmental friendliness of the experimental method.

The graphene (GR)/TiO₂ membrane was prepared by the sol-gel method and coated on the indium tin oxide (ITO) conductive glass, which showed high and stable photo(-electro)-catalytic activities to rhodamine B (Rh-B) in water. Characterization results showed that the GR was dispersed and wrapped in the needle-like TiO₂. With GR/TiO₂ membrane and simulated sunlight irradiation, the removal efficiency of Rh-B (10 mg l⁻¹ and pH at 5.4) arrived at 87.6% within 300 min. However, the higher removal efficiency for Rh-B reached to 97.8% by the photo-electro-catalytic degradation with the applied voltage 4 v for 30 min. The ·OH that generated in the photo-catalytic degradation process were responsible for Rh-B decomposition. The ·O₂⁻ played the significant role in the photo-electro-catalytic degradation of Rh-B. Furthermore, the decarboxylation was also occurred in the photo-electro-catalytic degradation for the Rh-B in water except for the deethylation and hydroxylation in the photo-catalytic degradation. In addition, the toxicities of the intermediates were calculated using the ECOSAR program and the EPIWIN software. The results indicated that the toxicities of intermediates from photo-electro-catalytic degradation for the Rh-B were higher than photo-catalytic degradation, due to the generation of decarboxylate.

Nonylphenols (NPs) are persistent organic pollutants (POPs) with estrogenic properties that can perform endocrine-disrupting activities. By using high-concentration NP as environmental selection pressure, one NP biodegradation strain named NPF-4 was isolated and purified from estuary sediment of the Moshui River. It was identified as Penicillium simplicissimum (PS1) by appearance and 18S rDNA analysis. In different culture situations, the strain mass growth and biodegradation ability were evaluated. Within 4-n-nonylphenol (4-n-NP) initial concentration of 20 mg L⁻¹, it could be degraded 53.76, 90.08, and 100.00 % at 3, 7, and 14 days, respectively. In feeding experiments, it showed that NPF-4 could use 4-n-NP as a sole carbon source. Based on seven products/intermediates detected with GC and LC-MS, a novel biopathway for 4-n-NP biodegradation was proposed, in which sequential hydroxylation, oxidation, and decarboxylation at terminal β-C atom may occur for 4-n-NP detoxification, even complete mineralization in the end.

The acidity of Ultisols (pH <5) is detrimental to crop production. Technologies should be explored to promote base saturation and liming effect for amelioration of Ultisol pH. Column leaching experiments were conducted to investigate the amelioration effects of canola straw (CS) and peanut straw (PS) in single treatment and in combination whether with alkaline slag (AS) or with lime on Ultisol profile acidity. The treatment without liming materials was set as control, and the AS and lime in single treatment are set for comparison. Results indicated that all the liming materials increase soil profile pH and soil exchangeable base cations at the 0–40-cm depth, except that the lime had amelioration effect just on 0 to 15-cm profile. The amelioration effect of the liming materials on surface soil acidity was mainly dependent on the ash alkalinity in organic materials or acid neutralization capacity of inorganic materials. Specific adsorption of sulfate (SO₄ ²⁻) or organic anions, decarboxylation of organic acids/anions, and the association of H⁺ with organic anions induced a “liming effect” of crop residues and AS on subsoil acidity. Moreover, SO₄ ²⁻ and chloride (Cl⁻) in PS, CS, and AS primarily induced base cations to move downward to subsoil and exchange with exchangeable aluminum (Al³⁺) and protons (H⁺). These anions also promoted the exchangeable Al to leach out of the soil profile. The CS was more effective than PS in decreasing soil acidity in the subsoil, which mainly resulted from higher sulfur (S) and Cl content in CS compared to PS. The CS combined with AS was the better amendment choice in practical agricultural systems.

The release of pharmaceuticals in the environment, as parent compounds, metabolites and transformation products, and the consequent risks posed to living organisms due to the unintended exposure of the latter to these chemicals are nowadays of increasing scientific concern. The development of advanced oxidation processes able to degrade these substances is in the core of the current research objectives, the main target being the removal of these compounds from wastewaters. Often the focus is on the removal of the parent compound only. However, these processes can form transformation products. Knowledge on the risk related to such transformation products is scarce. Among others, knowledge on their toxic effects and their biodegradability is of importance not only when they are present in the environment but also for the assessment of the advanced oxidation processes’ efficiency applied for their degradation. Photolytic (UV irradiation) and photocatalytic treatment (UV irradiation in the presence of TiO₂) of the fluoroquinolone ofloxacin were applied, and the biodegradability of the formed products was investigated using the Closed Bottle test (OECD 301 D). Various transformation products, formed both during the photo(cata)lytic treatment and the Closed Bottle test, were identified using chromatographic analysis with an ultra high-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) system. The transformation products formed during the phototreatments were found to be non-readily biodegradable as the biodegradation percentages were close to zero. The persistence of the various photo(cata)lytic transformation products during the Closed Bottle test may be attributed to the fluorine present in all the transformation products formed. The transformation products identified suggest that two transformation routes were present: decarboxylation and opening of the piperazinyl ring. Interestingly, it was observed that in the presence of a readily biodegradable carbon source (sodium acetate), the biodegradation percentage increased drastically for some of the photolytically treated samples. This was not the case for the photocatalytically treated samples, in which also mineralization of the parent compound was achieved faster. Further research is needed, however, in order to increase the understanding of the conditions that may lead to less potent and persistent substances during the application of such engineered or natural processes.