Visible-light-driven TiO2@Fe2O3/Chitosan nanocomposite with promoted photodegradation of meropenem and imipenem antibiotics by peroxymonosulfate.

This study assessed wastewater treatment by visible-light/Peroxymonosulfate process using its linking with TiO2@Fe3O4 nanoparticles coated on chitosan. Meropenem and Imipenem photodegradation was evaluated as a model-resistant contaminant by TiO2@Fe2O3/chitosan nanocomposite. The synthesised TiO2@Fe2O3/chitosan was characterised using various techniques. Fe2O3 and TiO2 nanoparticles on the chitosan surface were affirmed via XRD, EDX, and FTIR findings. The FESEM and TEM results verified the deposition of TiO2@Fe2O3 on the chitosan surface. Under optimum circumstances (pH = 4, catalyst dosage = 0.5 g/L, antibiotics concentration = 25 mg/L reaction time = 30 min, and PMS = 2 mM), maximum degradation efficiency was obtained at about 95.64 and 93.9% for Meropenem and Imipenem, respectively. Also, the experiments demonstrated that TiO2@Fe2O3/chitosan had a better performance than photolysis and adsorption by catalyst without visible light irradiation in degrading antibiotics. The scavenger tests confirmed that O2⋅-, SO4⋅-, HO⋅, and h+ are present simultaneously during the pollutant photodegradation process. After five recovery cycles, the system eliminated over 80 percent of antibiotics. It suggested that the catalyst's capacity to be reused may be cost-effective.

Evaluation of occurrence of organic, inorganic, and microbial contaminants in bottled drinking water and comparison with international guidelines: a worldwide review.

The aim of this study was to evaluate the levels of inorganic and organic substances as well as microbial contaminants in bottled drinking water on a global scale. The findings were compared to WHO guidelines, EPA standards, European Union (EU) directive, and standards drafted by International Bottled Water Association (IBWA). Our review showed that 46% of studies focused on the organic contaminants, 25% on physicochemical parameters, 12% on trace elements, 7% on the microbial quality, and 10% on microplastics (MPs) and radionuclides elements. Overall, from the 54 studies focusing on organic contaminants (OCs) compounds, 11% of studies had higher OCs concentrations than the standard permissible limit. According to the obtained results from this review, several OCs, inorganic contaminants (IOCs), including CHCl3, CHBrCl2, DEHP, benzene, styrene, Ba, As, Hg, pb, Ag, F, NO3, and SO4 in bottled drinking water of some countries were higher than the international guidelines values that may cause risks for human health in a long period of time. Furthermore, some problematic contaminants with known or unknown health effects such as EDCs, DBP, AA, MPs, and some radionuclides (40K and 222Rn) lack maximum permissible values in bottled drinking water as stipulated by international guidelines. The risk index (HI) for OCs and IOCs (CHBrCl2, Ba, As, and Hg) was higher than 1 in adults and children, and the value of HI for CHCl3 in children was more than 1. Thus, further studies are required to have a better understanding of all contaminants levels in bottled drinking water.

A salt resistant biosurfactant produced by moderately halotolerant Pseudomonas aeruginosa (AHV-KH10) and its application for bioremediation of diesel-contaminated sediment in saline environment.

A halotolerant bacterial strain was isolated from oily-contaminated sites of Persian Gulf, which characterized as Pseudomonas aeruginosa (AHV-KH10) by 16S rRNA gene sequencing. This strain was used for bioremediation of diesel-contaminated sediments. Biosurfactant production was initially screened by using oil displacement test and drop-collapse method, followed by measurement of surface tension (ST) of growth medium. Produced biosurfactant was a rhamnolipid type biosurfactant and lowered the ST to 33.4 mN/m at the given critical micelle concentration (CMC) of 75 mg/L. Addition of 3 CMC rhamnolipid, inoculums size of 15 mL, biodegradation in slurry phase and salinity level of 6% led totally to a diesel biodegradation rate of 70% for initial concentration of 1000 mg/kg after 35 days. The maximum diesel removal occurred at the salinity content of 6% indicating the moderately halo-tolerant characteristics of isolated strain. Evaluation of bacterial growth showed a biomass yield of 0.33 mg VSS/mg diesel in selected conditions. The field performance of Pseudomonas aeruginosa AHV-KH10 was proved through the removal of the TPH content in unwashed sediment, which varied from 2390 to 1875 mg/kg within four months.

Optimization of electro-kinetic process for remediation of soil contaminated with phenanthrene using response surface methodology.

The objective of this work was to investigate the modification of soil contaminated with phenanthrene (PHE) by electro-kinetic remediation (EKR) process using response surface methodology (RSM). The soil sample was obtained from the subgrades (0-30 cm) of an area close to Shahroud City, Northeast of Iran. The effect of variables such as initial pH, voltage, electrolyte concentration, and reaction time on PHE removal was studied. Based on the results obtained from the central composite design (CCD) experiment, the highest and lowest amount of PHE removal was 97 and 20%, respectively. In this study, the variables A, B, C, AB, AC, and C2 with a p value < 0.05 were significant model terms and the parameter of the lack of fit was not significant (p value = 0.0745). Findings indicated that the "predicted R-squared" of 0.9670 was in reasonable agreement with the "adj R-squared" of 0.9857 and the plot of residual followed a normal distribution and approximately linear. Also, the kinetic rates of the removal PHE by the EKR process best fitted with a first-order kinetic model (R2: 0.926). Results of the investigation of the effective variables showed that in values of pH 3, time of 168 h, voltage of 3 V, and electrolyte concentration of 4 mg/L, the removal efficiency of PHE reached 96.6%. Graphical abstract.

Remediation of PAHs contaminated soil using a sequence of soil washing with biosurfactant produced by Pseudomonas aeruginosa strain PF2 and electrokinetic oxidation of desorbed solution, effect of electrode modification with Fe3O4 nanoparticles.

This work aimed to investigate the performance of biosurfactant, produced by a halotolerant bacterial strain, Pseudomonas aeruginosa PF2, for desorption of PAHs from soil, followed by electrokinetic oxidation of the desorbed solution using Magnetite Nanoparticles Modified Graphite (MNMG). Pyrene (PYR), anthracene (ANT) and phenanthrene (PHE) were used as contamination model. Produced and extracted biosurfactant was characterized as rhamnolipid with Critical Micelle Concentration (CMC) of 60 mg/L and emulsification index (E24) value of 60.2% for n-hexadecane, 58.4% for n-heptane and 55.6% for n-Hexane, respectively. Results of LC-MS/MS analysis indicated the presence of seven major peaks at m/z of 677.5, 531.1, 649.3, 528.9, 475.1, 359 and 503.2, which corresponded to the deprotonated molecules of RhaRhaC12C10, RhaC12C10, RhaRhaC10C10, RhaC12:1C10, RhaC8C10, Rha-C12:2 and RhaC10C10, respectively. The maximum desorption of PAHs was derived at pH value of 6, CMC of 3 and contact time of 24 h. Modification of graphite electrode enhanced the PAH degradation significantly. In electrokinetic oxidation of desorbed solution, the best results were observed at pH value of 5, contact time of 6 h, voltage of 3 V and electrolyte concentration of 25 mg/L, with the average removal efficiency of higher than 99% for all studied PAHs.

Experimental data on adsorption of Cr(VI) from aqueous solution using nanosized cellulose fibers obtained from rice husk.

The aim of this study was to evaluate the efficiency of nano-sized cellulose obtained from rice husk for Cr(VI) adsorption. The effect of operational parameters including initial pH (3-10), contact time (0-120 min), adsorbent dosage (0.2-1.5 g/L), and initial Cr(VI) concentration (5-50 mg/L) were investigated according to one factor at time method. The results showed, in pH=6, contact time=100 min, adsorbent dose=1.5 g/L and 30 mg/L initial chromium concentration, the adsorption efficiency reached to 92.99%. Also Langmuir isotherm with (R2=0.998 at 303 °K) and pseudo-first-order kinetic model (R2=0.993) were the best models for describing the Cr(VI) adsorption reactions. The negative values of [Formula: see text] and positive value of [Formula: see text] showed that, the Cr(VI) adsorption on NCFs was endothermic and spontaneously process. Therefore, it can be concluded that the application this method is recommended for removing Cr(VI) from aqueous solutions.

Electrokinetic treatment of high saline petrochemical wastewater: Evaluation and scale-up.

High total dissolved solids (TDS) wastewater containing high amounts of organics with toxic and recalcitrant characteristics is a major concern in some petrochemical industries. This study was designed to evaluate a novel electrokinetic process for chemical oxygen demand (COD) removal. The removal of COD was carried out in some batch experiments in lab scale and effect of experimental factors such as the pH, current intensity, time, electrodes distances and TDS on the COD removal was evaluated. Also scale-up of the process was done in order to evaluate energy consumption. The obtained findings indicated that best conditions for COD removal were achieved in pH 5, current intensity of 0.5 A and electrodes distance of 2 cm. Pseudo-first-order kinetic model with rate constant of 0.0093 min-1 and significant coefficient of correlation (R2) 0.948 was the best fitted with experimental results. Energy consumption was 32 KWh.m-3 while 80 fold scaling up the reactor resulted in lower energy consumption of 2.1 KWh.m-3. Biodegradability improvement confirmed by BOD5/COD, average oxidation state (AOS) and carbon oxidation state (COS) indicators, Also GC chromatogram of the raw and treated wastewater showed removal and/or degradation of recalcitrant organics to more degradable and simpler compounds.