Advanced oxidation/reduction processes (AO/RPs) for wastewater treatment, current challenges, and future perspectives: a review.

Advanced oxidation/reduction processes (AO/RPs) are considered as effective water treatment technologies and thus could be used to solve the problem of water pollution. These technologies of wastewater treatment involve the production of highly reactive species such as •OH, H•, e-aq, SO4•-, and SO3•-. These radicals can attack the targeted contaminants present in aqueous media and result in their destruction. The efficiency of AO/RPs is highly affected by various operational parameters such as initial concentration of contaminant, solution pH, catalyst amount, intensity of light source, nature of oxidant and reductant used, and the presence of various ionic species in aquatic media. Among AO/RPs, the solar light-based AO/RPs are most widely used nowadays for contaminant removal from aqueous media because of their high environmental friendliness and cost effectiveness. By using these techniques, almost all types of pollutants can be easily removed from aquatic media within short intervals of time, and hence, the problem of water pollution can be solved effectively. This review focuses on various AO/RPs used for wastewater treatment. The effects of different operational parameters that affect the efficiency of these processes toward contaminant removal have been discussed. Besides, challenges and future recommendations are also briefly provided for the researchers in order to improve the efficiency of these processes.

Catalytic degradation of carbamazepine by surface-modified zerovalent copper via the activation of peroxymonosulphate: mechanism, degradation pathways and ecotoxicity.

In this research work, surface-modified nano zerovalent copper (nZVC) was prepared using a simple borohydride reduction method. The spectroscopic and crystallographic results revealed the successful synthesis of surface-modified nano zerovalent copper (nZVC) using solvents such as ethanol (ETOH), ethylene glycol (EG) and tween80 (T80). The as-synthesized material was fully characterized for morphological surface and crystal structural properties. The results indicated that EG provides an excellent synthesis environment to nZVC compared to ETOH and T80 in terms of good dispersion, high surface area and excellent catalytic properties. The catalytic efficiency of nZVC/EG was investigated alone and with peroxymonosulphate (PMS) in the absence of light. The degradation results demonstrated that the involvement of PMS synergistically boosted the catalytic efficiency of synthesized nZVC/EG material. Furthermore, the degradation products (DPs) of CBZ were determined by GC-MS and subsequently, the degradation pathways were proposed. The ecotoxicity analysis of the DPs was also explored. The proposed (nZVC/EG/PMS) system is economical and efficient and thus could be applied for the degradation of CBZ from an aquatic system after altering the degradation pathways in such a way that results in harmless products.

Comparison of oxidative stress levels during the third Trimester in normal pregnancy and preeclampsia.

BACKGROUND: The placenta is a complex transiently formed organ which plays a crucial role in the development of the foetus. As the placenta is responsible for maintaining pregnancy placental defects are mainly responsible for pregnancy-related issues. Preeclampsia is a pregnancy-related disorder due to uteroplacental insufficiency resulting from deficient remodelling of spiral arteries causing ischemic reperfusion injury which is finally responsible for the generation of reactive oxygen species and oxidative stress by the placenta. So, this study was planned to determine and compare serum levels of oxidative stress markers (ischemia-modified albumin and malondialdehyde) in preeclampsia and normal pregnancy in the third trimester. METHODS: Study design: Cross-sectional comparative study Settings Gynae/Obs Department and Pathology Laboratory, Lahore General Hospital, Lahore. Study population: 42 Pregnant females at 34-36 weeks of gestation were selected. Group 1 compromised 21 normal healthy pregnant females and group 2 included 21 preeclamptic patients. Sampling technique: non-probability purposive sampling. Blood samples were taken at 34-36 weeks of gestation. Serum was stored for ischemiamodified albumin and malondialdehyde. Data was analyzed using SPSS version 20. An Independent t-test was used to compare values between the groups during the third trimester. A pvalue of ≤0.05 was considered significant. RESULTS: Comparison of ischemia-modified albumin and malondialdehyde values between group I and group 2 showed a highly significant difference of pvalue of <0.001. CONCLUSIONS: Oxidative stress markers were higher in preeclamptic patients as compared to normal pregnant females during the third trimester suggesting the role of the placenta in oxidative stress.

Development of zerovalent iron and titania (Fe0/TiO2) composite for oxidative degradation of dichlorophene in aqueous solution: synergistic role of peroxymonosulfate (HSO5-).

Binary composite of zerovalent iron and titanium dioxide (Fe0/TiO2) was synthesized for the catalytic removal of dichlorophene (DCP) in the presence of peroxymonosulfate (PMS). The as-prepared composite (Fe0/TiO2) exhibits synergistic effect and enhanced properties like improved catalytic activity of catalyst and greater magnetic property for facile recycling of catalyst. The results showed that without addition of PMS at reaction time of 50 min, the percent degradation of DCP by TiO2, Fe0, and Fe0/TiO2 was just 5%, 11%, and 12%, respectively. However, with the addition of 0.8 mM PMS, at 10 min of reaction time, the catalytic degradation performance of Fe0, TiO2, and Fe0/TiO2 was significantly improved to 82%, 18%, and 88%, respectively. The as-prepared catalyst was fully characterized to evaluate its structure, chemical states, and morphology. Scanning electron microscopy results showed that in composite TiO2 causes dispersion of agglomerated iron particles which enhances porosity and surface area of the composites and X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FTIR) results revealed successful incorporation of Fe0, and oxides of Fe and TiO2 in the composite. The adsorption-desorption analysis verifies that the surface area of Fe0/TiO2 is significantly larger than bare Fe0 and TiO2. Moreover, the surface area, particle size, and crystal size of Fe0/TiO2 was surface area = 85 m2 g-1, particle size = 0.35 µm, and crystal size = 0.16 nm as compared to TiO2 alone (surface area = 22 m2 g-1, particle size = 4.25 µm, and crystal size = 25.4 nm) and Fe0 alone (surface area = 65 m2 g-1, particle size = 0.9 µm, and crystal size = 7.87 nm). The as-synthesized material showed excellent degradation performance in synthesized wastewater as well. The degradation products and their toxicities were evaluated and the resulted degradation mechanism was proposed accordingly. The toxicity values decreased in order of DP1 > DP5 > DP2 > DP3 > DP4 and the LC50 values toward fish for 96-h duration decreased from 0.531 to 67.2. This suggests that the proposed technology is an excellent option for the treatment of antibiotic containing wastewater.

A novel route for catalytic activation of peroxymonosulfate by oxygen vacancies improved bismuth-doped titania for the removal of recalcitrant organic contaminant.

In this work, bismuth-doped titania (BixTiO2) with improved oxygen vacancies was synthesized by sol-gel protocol as a novel peroxymonosulfate (PMS, HSO5-) activator. HSO5- and adsorbed oxygen molecules could efficiently be transformed into their respective radicals through defect ionization to attain charge balance after their trapping on oxygen vacancies of the catalyst. XRD study of BixTiO2 with 5 wt% Bi (5BiT) revealed anatase, crystalline nature, and successful doping of Bi into TiO2 crystal lattice. The particle size obtained from BET data and SEM observations was in good agreement. PL spectra showed the formation rates of •OH by 3BiT, 7BiT, 5BiTC, and 5BiT as 0.720, 1.200, 1.489, and 2.153 µmol/h, respectively. 5BiT catalyst with high surface area (216.87 m2 g-1) and high porosity (29.81%) was observed the excellent HSO5- activator. The catalytic performance of 0BiT, 3BiT, 5BiT, and 7BiT when coupled with 2 mM HSO5- for recalcitrant flumequine (FLU) removal under dark was 10, 27, 55, and 37%, respectively. Only 5.4% decrease in catalytic efficiency was observed at the end of seventh cyclic run. Radical scavenging studies indicate that SO4•- is the dominant species that caused 62.0% degradation. Moreover, strong interaction between Bi and TiO2 through Bi-O-Ti bonds prevents Bi leaching (0.081 mg L-1) as shown by AAS. The kinetics, degradation pathways, ecotoxicity, and catalytic mechanism for recalcitrant FLU were also elucidated. Cost-efficient, environment-friendly, and high mineralization recommends this design strategy; BixTiO2/HSO5- system is a promising advanced oxidation process for the aquatic environment remediation.

Mechanistic investigations on the removal of diclofenac sodium by UV/S2O82-/Fe2+, UV/HSO5-/Fe2+ and UV/H2O2/Fe2+-based advanced oxidation processes.

This study reports the comparative removal of an emerging contaminant diclofenac sodium (DCF) by UV-254 nm-based advanced oxidation processes (AOPs), i.e. UV/S2O82-/Fe2+, UV/HSO5-/Fe2+ and UV/H2O2/Fe2+ processes. The results demonstrated that by applying [DCF]0 = 0.30 mM and [H2O2]0 = [S2O82-]0 = [HSO5-]0 = 3 mM, kapp values were 0.082, 0.166, 0.221, 0.485 and 2.014 min-1 for UV-only, UV/Fe2+, UV/H2O2/Fe2+, UV/S2O82-/Fe2+ and UV/HSO5-/Fe2+ processes, respectively. At different [DCF]0 from 0.30 to 0.90 mM, the degradation rate was increased from 0.01 mM min-1 to 0.12 mM min-1, while the corresponding kapp values were decreased from 2.01 min-1 to 1.04 min-1. The removal performance of the applied AOP was significantly influenced by the presence of natural water contaminants (NO3-, Cl-, HCO3-, SO42- and humic acid (HA)) and [pH]0. The inhibition of these natural water contaminants on the removal of DCF by UV/HSO5-/Fe2+ process was in the order of HA > NO2- > SO42- > HCO3- ≈ Cl- > NO3-. Furthermore, seven (07) degradation products (DPs) of DCF were explored by UPLC-MS/MS and accordingly degradation pathways of DCF were suggested. The practical applications of the proposed AOPs towards the removal of DCF were further strengthened by calculating total organic carbon removal and toxicity assessment.

Bismuth-Doped Nano Zerovalent Iron: A Novel Catalyst for Chloramphenicol Degradation and Hydrogen Production.

In this study, we showed that doping bismuth (Bi) at the surface of Fe0 (Bi/Fe0, bimetallic iron system)-synthesized by a simple borohydride reduction method-can considerably accelerate the reductive degradation of chloramphenicol (CHP). At a reaction time of 12 min, 62, 68, 74, 95, and 82% degradation of CHP was achieved with Fe0, Bi/Fe0-1 [1% (w/w) of Bi], Bi/Fe0-3 [3% (w/w) of Bi], Bi/Fe0-5 [5% (w/w) of Bi], and Bi/Fe0-8 [8% (w/w) of Bi], respectively. Further improvements in the degradation efficiency of CHP were observed by combining the peroxymonosulfate (HSO5 -) with Bi/Fe0-5 (i.e., 81% by Bi/Fe0-5 and 98% by the Bi/Fe0-5/HSO5 - system at 8 min of treatment). Interestingly, both Fe0 and Bi/Fe0-5 showed effective H2 production under dark conditions that reached 544 and 712 µM by Fe0 and Bi/Fe0-5, respectively, in 70 mL of aqueous solution containing 0.07 g (i.e., at 1 g L-1 concentration) of the catalyst at ambient temperature.

Morbidity and Mortality Associated With Pediatric Critical Mediastinal Mass Syndrome.

Objective The critical mediastinal mass syndrome (CMMS) is a life-threatening condition and is challenging for physicians. We analyse the clinicopathological profile and outcome of CMMS from a large tertiary-care pediatric oncology center in Pakistan. Methods We retrospectively reviewed the medical record of a tertiary-care hospital in Pakistan from April 2017 to September 2019 for all children (1 month-16 years) who presented with an anterior mediastinal mass (AMM). A CMMS case is defined as a child with an AMM presenting with cardiorespiratory compromise and needing intensive care support. Demographic data, clinical profile, pathological diagnosis, and outcome of all such children were recorded. Descriptive statistics were applied using the Statistical Package for the Social Sciences (SPSS), version 22 (IBM Corp., Armonk, NY). Results Of the total 221 mediastinal masses, 61 children were diagnosed as CMMS and enrolled in the study. The mean age was 9 ± 3.3 years, and 68.9%% were male; 65.6% of patients had a weight for age less than the fifth percentile. A total of 49.2% of patients had a duration of illness of more than one month before diagnosis. Fever (97.6%) and lymphadenopathy (82%) were the most common findings, along with respiratory and cardiovascular signs and symptoms; 9.8% had superior vena cava syndrome. The pericardial effusion was present in 54.6% and 27.9% had pleural effusion. Peripheral blood flow cytometry made the diagnosis in 59%, peripheral lymph node biopsy in 13%, mediastinal core biopsy in 5%, and pleural fluid flow cytometry in one case; 62.3% had a white blood cell count of >100,000/mm3. A total of 72.1% (n=44) cases were diagnosed as T-cell acute lymphoblastic leukemia in our cohort. Clinical and laboratory tumor lysis syndrome developed in 10% and 73% of cases, respectively. Mechanical ventilation was required in 9.8% of the cohort. Mortality was reported in 10 (16.4%) patients. Conclusion We found that the 100% fatality rate with controlled positive pressure ventilation and spontaneous breathing is ideal. Tumour lysis syndrome was the most common morbidity in our cohort.

Oxidative removal of brilliant green by UV/S2O82‒, UV/HSO5‒ and UV/H2O2 processes in aqueous media: A comparative study.

The removal of brilliant green (BG), a toxic organic and cationic dye, has been examined by UV/S2O82- (PS), UV/HSO5- (PMS) and UV/H2O2 processes. BG showed insignificant direct photolysis at 254 nm (i.e., 8.6% after 30 min). However, enhanced BG degradation was observed in UV/PS, UV/PMS and UV/H2O2 systems as revealed from 63.1, 47.0 and 34.8% BG degradation, respectively, at 30 min of reaction time, using 0.05 mM BG and 1.0 mM oxidant initial concentration. The bimolecular rate constants of OH and SO4- with BG were determined to be 2.35 × 109 and 2.21 × 109 M-1 s-1, respectively. Electrical energy per order (EE/O) values for UV/PS, UV/PMS and UV/H2O2 processes were calculated to be 5.4, 6.8, and 7.8 KWh/m3/order, respectively. The addition of humic acid (HA) and inorganic anions inhibited the degradation of BG by UV/PS in the order of NO2- > HA > HCO3- > Cl-  > NO3- ≈ SO42-. The results of frontier electron densities (FEDs) showed that C-atom holding the three rings (C7), and C-atoms at para positions to N-alkyl groups of the two rings (C4 and C14) are the predominant sites for radical addition. Furthermore, nine degradation products (DPs) of BG were detected experimentally using LC/MS/MS.

Degradation of quinolone antibiotic, norfloxacin, in aqueous solution using gamma-ray irradiation.

This study reports the efficiency of gamma-ray irradiation to degrade quinolone antibiotic, norfloxacin, in aqueous solution. Laboratory batch experiments were conducted to determine the "pseudo-first" order degradation kinetics of norfloxacin in the concentration ranges of 3.4-16.1 mg L(-1) by gamma-ray irradiation. The dose constant was found to be dependent on the initial concentration of norfloxacin and gamma-ray irradiation dose rate (D r). The saturation of norfloxacin sample solutions with N2, air or N2O, and the presence of tert-butanol and 2-propanol showed that (•)OH played more crucial role in the degradation of norfloxacin. The second order rate constants of (•)OH, eaq (-), and (•)H with norfloxacin were calculated to be 8.81 × 10(9), 9.54 × 10(8), and 1.10 × 10(9) M(-1) s(-1), respectively. The effects of various additives including CO3 (2-), HCO3 (-), NO3 (-), NO2 (-), and thiourea and the pH of the medium on the degradation of norfloxacin were also investigated. Norfloxacin degradation was lower in surface water and wastewater than in ultrapure water. Several degradation byproducts of norfloxacin were identified from which the possible degradation pathway was proposed.

Role of eaq⁻, ·OH and H· in radiolytic degradation of atrazine: a kinetic and mechanistic approach.

The degradation of atrazine was investigated in aqueous solution by gamma-ray irradiation. 8.11 µM initial atrazine concentration could be completely removed in N2 saturated solution by applying 3500 Gy radiation dose at a dose rate of 296 Gy h(-1). Significant removal of atrazine (i.e., 39.4%) was observed at an absorbed dose of 1184 Gy in air saturated solution and the removal efficiency was promoted to 50.5 and 65.4% in the presence of N2O and N2 gases, respectively. The relative contributions of hydrated electron, hydroxyl radical and hydrogen radical toward atrazine degradation were determined as ratio of observed dose constant (kobs) and found to be 5: 3: 1 for keaq(-): k·OH: kH·, respectively. The degradation efficiency of atrazine was 69.5, 55.6 and 37.3% at pH 12.1, 1.7 and 5.7, respectively. A degradation mechanism was proposed based on the identified degradation by-products by gas chromatography-mass spectrometry. Taking the relative contributions of oxidative and reductive species to atrazine degradation into account, reductive pathway proved to be a better approach for the radiolytic treatment of atrazine contaminated water.