The combination of biochar (BC) and peroxymonosulfate (PMS) is a cost-effective strategy for removing pollutants; however, optimization of BC synthesis and reaction parameters is essential. In this work, one-step pyrolysis was used for biochar production, and trimethoprim (TRIM) antibiotic degradation was investigated in the presence of PMS-containing biochar suspension. For the production of an effective biochar catalyst, grass pellets as the raw material, a pyrolysis temperature of 700 degrees C, and a ball-milling time of 15 min proved optimal for TRIM degradation. The effect of pyrolysis temperature highlighted that the appropriate degree of graphitization is a key factor in catalytic efficiency, while persistent free radicals (PFRs) on the surface play only a moderate role. Ball milling significantly reduced the amount of biochar (3.0 gdm-3-* 0.5 gdm-3) and PMS (2.0 mM-* 0.2 mM) required for TRIM degradation. In addition to the increased surface area, the enhanced density of structural defects serves as active sites, and changes in surface oxidation state also contribute to the enhanced efficiency of ball-milled biochar. The effect of radical scavengers clearly confirmed that, without ball milling, the main reactive species is 1O2, and the non-radical pathway leads to the conversion of TRIM. In the case of ball-milled biochar, radical (HO center dot and SO4 center dot-) formation is favored, and the radical-based pathway dominates in the TRIM conversion. Although treated wastewater reduced the degradation efficiency, this effect was mitigated by higher BC and PMS doses. Furthermore, the results regarding the reusability of BC and its successful regeneration by UV/PDS underscore the potential of this process.

UV (254 nm) and UV/VUV (254/185 nm) photolysis, ozonation, and O-3/UV combination were investigated and compared for the transformation of two sulfonamide (SAs) antibiotics, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP). Change in toxicity, the effect of bacteria growth inhibition of the treated solutions, and the cost-efficiency of the methods were studied. In UV/VUV radiated solutions, the formation of (OH)-O-center dot results in the doubled transformation rate. The relative contribution of various ROS ((OH)-O-center dot, O-1(2), O-2(center dot-)) to the transformations were also investigated in the case of UV and UV/VUV photolysis. Both SAs can be eliminated ten times faster during ozonation than UV photolysis; but conversion via ozonation is associated with the formation of products with low reactivity to ozone and has biological effects. The O-3/UV process did not enhance the transformation rate but positively affected mineralization and significantly decreased the ecotoxicity of the treated solutions. Ozonation was cost-effective, but O-3/UV is a much safer technology to minimize environmental impacts because it effectively reduces the ecotoxicity and the bacterial growth inhibition effect of the treated solution. The observed differences between SMT and SMP are primarily related to the transformation of the N-containing rings. Our results showed a correlation between the reactivity of the N-containing groups of SAs, the rate of mineralization, and the change in ecotoxicity and antibacterial effect and emphasized the need for toxicological characterization of the treated samples. The removal of parent compounds is not sufficient to avoid the release of toxic substances into the environment.

The VUV (lambda < 200 nm) photolysis can be used to eliminate organic substances without the addition of oxidant due to the efficient generation of OH from water. Two VUV light sources are commercially available: the low-pressure mercury vapor (LPM) and the Xe-excimer lamp, which emit 185/254 nm and 172 nm photons, respectively. This study compares the efficiency of the UV/VUV185nm and VUV172nm photolysis in removing four sulfonamides (SAs) and trimethoprim (TRIM) antibiotics. For the LPM lamp, 254 nm UV radiation ((4.21 +/- 0.08) x 10(-6) mol(photon) s(-1)) can contribute to the transformation of target substances besides the OH generated by the 185 nm VUV light. The VUV photon flux (1.02 x 10(-5) mol(photon) s(-1)) of the Xe-excimer lamp significantly exceeded that of the LPM lamp (3.97 x 10(-7) mol(photon) s(-1)); as H2O2 formation in pure water reflected, however, the efficiency of the transformation rate of the target substances was just slightly faster. For the LPM lamp, in addition to the direct UV photolysis of SAs, the 254 nm light enhances the OH formation via H2O2 photolysis, thereby partially compensating for the low VUV185nm photon flux. The high VUV172nm photon flux was primarily manifested in mineralization efficiency and not in the transformation rate of target compounds. The short penetration depth of 172 nm light favors the recombination of primary radicals and decreases the efficiency. The effect of the matrix and matrix components is complex; they act as a radical scavenger or (V)UV filter. The change of radical set and the role of the formed secondary radicals (Cl, Cl-2(-), and CO3-) in transformation must be considered.

The persulfate-based advanced oxidation processes employing heterogeneous photocatalysts to generate sulfate radicals (SO4•−) from peroxydisulfate ion (PDS, S2O82−) have been extensively investigated to remove organic pollutants. In this work, BiOX (X = Cl, Br, and I) photocatalysts were investigated to activate PDS and enhance the transformation rate of various organic substances under UV (398 nm) and Vis (400–700 nm) radiation. For BiOCl and BiOBr, in addition to excitability, the light-induced oxygen vacancies are decisive in the activity. Although without organic substances, the BiOI efficiency highly exceeds that of BiOBr and BiOCl for PDS activation (for BiOI, 15–20%, while for BiOBr and BiOCl, only 3–4% of the PDS transformed); each BiOX catalyst showed enhanced activity for 1,4-hydroquinone (HQ) transformation due to the semiquinone radical-initiated PDS activation. For sulfamethoxypyridazine (SMP), the transformation is driven by direct charge transfer, and the effect of PDS was less manifested. BiOI proved efficient for transforming various organic substances even under Vis radiation. The efficiency was enhanced by PDS addition (HQ is wholly transformed within 20 min, and SMP conversion increased from 40% to 90%) without damaging the catalyst; its activity did change over three consecutive cycles. Results related to the well-adsorbed trimethoprim (TRIM) and application of biologically treated domestic wastewater as a matrix highlighted the limiting factors of the method and visible light active photocatalyst, BiOI.

The increasing prevalence of water insoluble or poorly soluble drugs calls for the development of new formulation methods. Common approaches include the reduction of particle size and degree of crystallinity. Pulsed laser ablation is a clean technique for producing sub-micrometre sized drug particles and has the potential to induce amorphization. We studied the effect of femtosecond pulsed laser ablation (ELI ALPS THz pump laser system: λc = 781 nm, τ = 135 fs) on meloxicam in distilled water and in air. The ablated particles were characterized chemically, morphologically and in terms of crystallinity. We demonstrated that femtosecond laser ablation can induce partial amorphization of the particles in addition to a reduction in particle size. In the case of femtosecond pulsed laser ablation in air, the formation of pure meloxicam spheres showed that this technique can produce amorphous meloxicam without the use of excipients, which is a unique result. We also aimed to describe the ablation processes in both investigated media.

The persulfate-based advanced oxidation process is a promising method for degrading organic pollutants. Herein, TiO2 and ZnO photocatalysts were combined with the peroxydisulfate ion (PDS) to enhance the efficiency. ZnO was significantly more efficient in PDS conversion and SO4•− generation than TiO2. For ZnO, the PDS increased the transformation rate of the trimethoprim antibiotic from 1.58 × 10−7 M s−1 to 6.83 × 10−7 M s−1. However, in the case of TiO2, the moderated positive effect was manifested mainly in O2-free suspensions. The impact of dissolved O2 and trimethoprim on PDS transformation was also studied. The results reflected that the interaction of O2, PDS, and TRIM with the surface of the photocatalyst and their competition for photogenerated charges must be considered. The effect of radical scavengers confirmed that in addition to SO4•−, •OH plays an essential role even in O2-free suspensions, and the contribution of SO4•− to the transformation is much more significant for ZnO than for TiO2. The negative impact of biologically treated domestic wastewater as a matrix was manifested, most probably because of the radical scavenging capacity of Cl− and HCO3−. Nevertheless, in the case of ZnO, the positive effect of PDS successfully overcompensates that, due to the efficient SO4•− generation. Reusability tests were performed in Milli-Q water and biologically treated domestic wastewater, and only a slight decrease in the reactivity of ZnO photocatalysts was observed.

The chlorination used in water treatment plants can promote the formation of toxic compounds, which can be minimized by substituting free available chlorine (FAC) with chlorine dioxide (ClO2). Besides disinfection, combining ClO2 with UV radiation leads to the efficient elimination of organic substances. This work employed a lab-made reactor equipped with LEDs emitting at 367 nm with adjustable photon flux to investigate the efficiency of the UVA/ClO2 process and the formation of hydroxylated and chlorinated products during the degradation of phenol and coumarin. The degradation of coumarin was investigated in a central composite design and depended on the ClO2 concentration and pH. Increasing the ClO2 concentration was necessary to promote the degradation. In higher ClO2/phenol ratios, 80% of the total phenolic compounds were removed at pH 3, 5.5, and 8. The mineralization efficiency increased with the pH, along with the concentration of chlorinated compounds, indicating these products are more persistent than the hydroxylated ones. The UVA/ClO2 process was advantageous in removing and mineralizing phenol and coumarin if compared to direct oxidation, but the process needs to be improved to minimize the formation of chlorinated organic products, and elimination of ClO2- and ClO3- requires post-treatment method.

VUV (185 nm) and UV light (254 nm) was recently used to promote the performance of UV-based advanced oxidation processes.In this study, UV and UV/VUV photolysis was combined with the peroxodisulfate process (UV/PDS and VUV/UV/PDS) for enhanced degradation of trimethoprim (TRIM, c0 = 1.0 × 10 -4 M) antibiotic from waters.Without PDS, the efficiency of UV/VUV photolysis exceeds that of UV photolysis due to the • OH formation.The addition of PDS (5.0×10 -4 M -3.0×10 -3 M) highly enhanced the transformation and mineralization rate in both cases.The relative contribution of radical-based reactions ( • OH and SO4 •-) were studied using terc-butanol, a radical scavenger.The contribution of • OH and SO4 •-to the transformation and mineralization depended on the PDS concentrationabove 1.0×10 -3 M PDS, the SO4 •-became the dominant reaction partner even in the case of UV/VUV photolysis.The effect of biologically treated wastewater as a matrix and its main inorganic components, such as HCO3 -and Cl -were also studied.The results proved that, however, both inorganic ions react with • OH and SO4 •-, the reactions between TRIM and formed CO3 •-and Cl • are involved in the conversion.The AOX content of the treated solution increased in the presence of Cl -, and this effect was moderated in the presence of HCO3 -.

In this work, the application of high-power LED365nm and commercial, low-price LED398nm for heterogeneous photocatalysis with TiO2 and ZnO photocatalysts are studied and compared, focusing on the effect of light intensity, photon energy, quantum yield, electrical energy consumption, and effect of matrices and inorganic components on radical formation. Coumarin (COU) and its hydroxylated product (7-HC) were used to investigate operating parameters on the •OH formation rate. In addition to COU, two neonicotinoids, imidacloprid and thiacloprid, were also used to study the effect of various LEDs, matrices, and inorganic ions. The transformation of COU was slower for LED398nm than for LED365nm, but r07-HC/r0COU ratio was significantly higher for LED398nm. The COU mineralization rate was the same for both photocatalysts using LED365nm, but a significant difference was observed using LED398nm. The impact of matrices and their main inorganic components Cl− and HCO3− were significantly different for ZnO and TiO2. The negative effect of HCO3− was evident, however, in the case of high-power LED365nm and TiO2, and the formation of CO3•− almost doubled the r07-HC and contributes to the conversion of neonicotinoids by altering the product distribution and mineralization rate.

The UV, UV/VUV photolysis and their combination with persulfate (S2O82−) were studied for the elimination of trimethoprim and 5-fluorouracil. Methods were examined in terms of transformation and mineralization rate and the matrix effect. The relative contribution of the direct UV photolysis and radical-based reactions (•OH, SO4•−) were also investigated. Without S2O82−, the efficiency of UV/VUV photolysis highly exceeds that of UV photolysis due to the •OH formation, while in the presence of S2O82−, the dominant reaction partner is SO4•−. However, SO4•−-based methods proved to be efficient for both transformation and mineralization; they are sensitive for the matrix components.

The photocatalytic performances of doped and non-doped TiO2 photocatalysts (TiO2-s) were compared under solar and various types of artificial irradiation using phenol as a model contaminant. Non-doped (mainly anatase phase) TiO2-s had significantly higher photocatalytic efficiency than highly visible-light-active TiO2-s under natural solar irradiation. To explain these unexpected results, we measured the wavelength dependence of photocatalytic efficiency at six different wavelength ranges (λ = 300–650 nm). For this purpose, UV fluorescence tubes and five LED lights of different colors (violet, blue, green, yellow, and red) were used to activate the photocatalysts. The photon fluxes of the irradiation were measured, and apparent quantum yields were calculated for all irradiation conditions. The highest apparent quantum yield was 1.43% for our own TiO2 (prepared via flame hydrolysis) under UV irradiation. However, apparent quantum yields were significantly lower (by 1–2 orders of magnitude) in the visible range, even for the most visible-light-active TiO2.

The comparison of the efficiency of the commercially available photocatalysts, TiO2 and ZnO, irradiated with 365 nm and 398 nm light, is presented for the removal of two antibiotics, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP). The •OH formation rate was compared using coumarin, and higher efficiency was proved for TiO2 than ZnO, while for 1,4-benzoquinone in O2-free suspensions, the higher contribution of the photogenerated electrons to the conversion was observed for ZnO than TiO2, especially at 398 nm irradiation. An extremely fast transformation and high quantum yield of SMP in the TiO2/LED398nm process were observed. The transformation was fast in both O2 containing and O2-free suspensions and takes place via desulfonation, while in other cases, mainly hydroxylated products form. The effect of reaction parameters (methanol, dissolved O2 content, HCO3− and Cl−) confirmed that a quite rarely observed energy transfer between the excited state P25 and SMP might be responsible for this unique behavior. In our opinion, these results highlight that “non-conventional” mechanisms could occur even in the case of the well-known TiO2 photocatalyst, and the effect of wavelength is also worth investigating.

Recently, the number of water insoluble and poorly soluble drug compounds has increased significantly. Therefore, growing interest has been witnessed in different particle size reduction techniques to improve the dissolution rates, transport characteristics and bioavailability of drugs. Laser ablation has proven to be an alternative method to the production of nano- and micrometre-sized drug particles without considerable chemical damage. We present the nanosecond laser ablation of drug pastilles in distilled water, targeting meloxicam, a poorly water soluble nonsteroidal anti-inflammatory drug, at different laser wavelengths (248 nm, 532 nm and 1064 nm). Besides chemical characterization, crystallinity, morphology and particle size studies, the mechanism of the particle generation process was examined. The applicability of ablated particles in drug formulation was investigated by solubility, cytotoxicity and anti-inflammatory effect measurements. We showed that laser ablation is a clean, efficient and chemically non-damaging method to reduce the size of meloxicam particles to the sub-micrometre–few micrometre size range, which is optimal for pulmonary drug delivery. Complemented by the excellent solubility (four to nine times higher) and anti-inflammatory (four to five times better) properties of the particles compared to the initial drug, laser ablation is predicted to have wider applications in the development of drug formulations.

Pharmaceuticals and pesticides are emerging contaminants problematic in the aquatic environment because of their adverse effects on aquatic life and humans. In order to remove them from water, photocatalysis is one of the most modern technologies to be used. First, newly synthesized photocatalysts were successfully prepared using a sol–gel method and characterized by different techniques (XRD, FTIR, UV/Vis, BET and SEM/EDX). The photocatalytic properties of TiO2, ZnO and MgO nanoparticles were examined according to their removal from water for two antibiotics (ciprofloxacin and ceftriaxone) and two herbicides (tembotrione and fluroxypyr) exposed to UV/simulated sunlight (SS). TiO2 proved to be the most efficient nanopowder under UV and SS. Addition of (NH4)2S2O8 led to the faster removal of both antibiotics and herbicide fluroxypyr. The main intermediates were separated and identified for the herbicides and antibiotic ciprofloxacin. Finally, the toxicity of each emerging pollutant mixture and formed intermediates was assessed on wheat germination and biomass production.

The widely investigated heterogeneous photocatalysis offers an environmentally friendly, efficient, and versatile solution for several environmental problems. Among others, the removal of harmful organic pollutants and the generation of H2 via water splitting are well-known and most widely studied applications. The process is based on the charge separation caused by the excitation of semiconductor photocatalyst via photon absorption. Due to the intensive development of material science, in addition to the well-known TiO2 and ZnO, several new semiconductor materials have been designed and synthesized to increase the efficiency of heterogeneous photocatalysis and utilization of solar and/or visible light. This chapter describes the principles and mechanisms of heterogeneous photocatalysis, including the formation of photogenerated charge carriers, the role of different reactive species, and the effect of key parameters on the efficiency.

This comparative study is about the heterogeneous photocatalytic degradation of two neonicotinoids, namely imidacloprid and thiacloprid, focusing on the differences and similarities in their transformation and mineralization and the effect of various additives, matrices, and their inorganic components. Besides the dominant role of •OH, which was confirmed by the effect of pH and radical scavengers, the direct charge transfer may also contribute to the transformation, especially for imidacloprid; partly due to its enhanced interaction with the TiO2 surface. There was a significant difference in the change of ecotoxicity, which decreased for thiacloprid but varied according to the maximum curve for imidacloprid, and interpreted by the effect of NO3− formed. Dehalogenation and mineralization were fast and occurred in parallel with the neonicotinoid degradation; however, 20–25% organic carbon could not be removed, suggesting the formation of hardly oxidizable products. The fluorination of the TiO2 has no significant effect on the transformation rates, but changed the product distribution, enhanced the dechlorination rate, and hindered the mineralization, confirming •OH-initiated formation of the hardly oxidizable intermediates. The negative effect of tap water and biologically treated domestic wastewater was significant. Although HCO3− caused a slower transformation, the effect of matrices cannot be interpreted solely by the radical scavenging capacity of their organic and inorganic content.

BiOI, BiOCl, and their composites (BiOI:BiOCl) with molar ratios from 95:5 to 5:95 were synthesized and tested in the transformation of methyl orange (MO) and sulfamethoxypyridazine (SMP) antibiotic, using three various LED light sources: UV LEDs (398 nm), cool and warm white LEDs (400-700 nm). The 80:20 BiOI:BiOCl photocatalyst showed the best adsorption capacity for MO and enhanced activity compared to BiOI and BiOCl. The apparent quantum yield (Φapp) of the MO and SMP transformation for cool and warm white light was slightly lower than for 398 nm UV radiation. The effect of methanol and 1,4-benzoquinone proved that the transformation is initiated mainly via direct charge transfer, resulting in the demethylation of MO and SO2 extrusion from SMP. The change of photocatalytic efficiency was followed during three cycles. After the first one, the transformation rates decreased, but there was no significant difference between the second and third cycles. The decreased efficiency is most probably caused by the intermediates, whose continuous accumulation was observed during the cycles. Ecotoxicity measurements confirmed that no toxic substances were leached from the catalyst, but the transformation of both MO and SMP results in toxic intermediates. Using 80:20 BiOI:BiOCl and LED light source, the energy requirement of the removal is about half of the value determined using TiO2 and a mercury vapor lamp. The effect of some components of wastewater (Cl-, HCO3- and humic acids), pH, and two matrices on the composite photocatalysts' efficiency and stability were also investigated.

In the present study, a commercial TiO2, several BiVO(4)photocatalysts, a WO(3)nanomaterial, and their composites were used to prepare photocatalytic polyvinylidene fluoride (PVDF) ultrafilter membranes. Their photocatalytic activities and the effects of coatings on the filtration of oil-in-water emulsion (crude oil; c(oil)= 100 mg L-1) were investigated. Fluxes, filtration resistances, purification efficiencies, and fouling resistance abilities-like flux decay ratios (FDRs) and flux recovery ratios (FRRs)-were compared. The solar light-induced photocatalytic decomposition of the foulants was also investigated. WO(3)was used as a composite component to suppress the electron-hole recombination with the goal of achieving higher photocatalytic activity, but the presence of WO(3)was not beneficial concerning the filtration properties. However, the application of TiO2, one of the investigated BiVO(4)photocatalysts, and their composites was also beneficial. In the case of the neat membrane, only 87 L m(-2)h(-1)flux was measured, whereas with the most beneficial BiVO(4)coating, 464 L m(-2)h(-1)flux was achieved. Pure BiVO(4)coating was more beneficial in terms of filtration properties, whereas pure TiO(2)coating proved to be more beneficial concerning the photocatalytic regeneration of the membrane. The TiO2(80%)/BiVO4(20%) composite was estimated to be the most beneficial combination taking into account both the aspects of photocatalytic activity and filtration properties.