Competitive adsorption of As(V) and Sb(V) at environmentally relevant concentrations onto ferrihydrite was investigated. Batch experiments and XPS analyses confirmed that in a binary system, the presence of Sb(V) exhibited a slight synergistic effect on As(V) adsorption. XPS analyses showed that As(V) and Sb(V) adsorption led to obvious diminishment of Fe–O–Fe and Fe–O–H bonds respectively. At pH of 9, a more significant decrease of Fe–O–Fe was observed in the binary system than that in a single system, indicating that As(V) displayed an even stronger interaction with lattice oxygen atoms under competitive conditions. Basically, ionic strength demonstrated a negligible or positive influence on As(V) and Sb(V) adsorption in binary system. Study of adsorption sequence also indicated that the presence of Sb(V) showed a promotion effect on As(V) adsorption at neutral pHs. Considering that co-contamination of As and Sb in waters has been of great concern throughout the world, our findings contributed to a better understanding of their distribution, mobility, and fate in environment.

The present work analyzes the effect of antioxidants on engine combustion performance of a multi-cylinder diesel engine fueled with PB30 and PB50 (30 and 50 vol.% palm biodiesel (PB)). Four antioxidants namely N,N′-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-1,4-phenylenediamine (NPPD), 2(3)-tert-Butyl-4-methoxyphenol (BHA), and 2-tert-butylbenzene-1,4-diol (TBHQ) were added at concentrations of 1000 and 2000 ppm to PB30 and PB50. TBHQ showed the highest activity in increasing oxidation stability in both PB30 and PB50 followed by BHA, DPPD, and NPPD respectively, without any negative effect on physical properties. Compared to diesel fuel, PB blends showed 4.61–6.45% lower brake power (BP), 5.90–8.69% higher brake specific fuel consumption (BSFC), 9.64–11.43% higher maximum in cylinder pressure, and 7.76–12.51% higher NO emissions. Carbon monoxide (CO), hydrocarbon (HC), and smoke opacity were reduced by 36.78–43.56%, 44.12–58.21%, and 42.59–63.94%, respectively, than diesel fuel. The start of combustion angles (SOC) of PB blends was − 13.2 to − 15.6 °CA BTDC, but the combustion delays were 5.4–7.8 °CA short compared to diesel fuel which were − 10 °CA BTDC and 11°CA respectively. Antioxidant fuels of PB showed higher BP (1.81–5.32%), CO (8.41–24.60%), and HC (13.51–37.35%) with lower BSFC (1.67–7.68%), NO (4.32–11.53%), maximum in cylinder pressure (2.33–4.91%) and peak heat release rates (HRR) (3.25–11.41%) than baseline fuel of PB. Similar SOC of − 13 to − 14 °CA BTDC was observed for PB blended fuels and antioxidants. It can be concluded that antioxidants’ addition is effective in increasing the oxidation stability and in controlling the NOx emissions of palm biodiesel fuelled diesel engine.

The photodegradation of antibiotic metronidazole (MNZ) was systematically studied and compared by using aqueous suspensions of TiO₂ and ZnO catalysts under 100-W UV irradiation. The degradation conditions were optimized using the central composite design and response surface methodology. The optimal photodegradation conditions obtained were at pH 6.0 with 1.5 g L⁻¹ of TiO₂ (86.10% removal for 50 mg L⁻¹ MNZ) and at pH 9.5 with 0.5 g L⁻¹ of ZnO (60.32% removal for 30 mg L⁻¹ MNZ) after 60-min irradiation at 20 °C. The degradation efficiency in the presence of TiO₂ was higher than that of ZnO. The participation of active species such as hydroxyl radicals (OH·), holes (h⁺), and superoxide radicals (O₂⁻·) during MNZ photodegradation over TiO₂ and ZnO catalysts was also examined. Experimental results showed that MNZ oxidation was mainly driven by the presence of holes and superoxide radicals. Totally, 10 major intermediates were detected in UV/TiO₂ and UV/ZnO photocatalysis of MNZ using LC-QTof/MS system, in which 5 same intermediates were found. The remaining different intermediates led to the variations of degradation pathways of both processes. Moreover, some bigger transformation products than the parent MNZ were detected.

The increase in the frequency of exposure to gasoline fumes and the growing incidence of infertility among humans has been a major concern and subject of discussion over the years in Nigeria. We therefore present the reproductive effect of gasoline fumes on inhalation exposure in 40 male albino rats. The rats were randomized into five experimental treatments (T) with eight rats per treatment. T1 (control) was exposed to distilled water while T2, T3, T4, and T5 were exposed to gasoline fumes in exposure chambers for 1, 3, 5, and 9 h daily respectively for 12 weeks. Serum level of testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxidative stress markers in the testicular tissue, epididymal sperm health assessment, and testicular histopathology of the rats were used as a diagnostic marker of reproductive dysfunction. Significant (p < 0.05) alterations in the levels of all the reproductive hormones and oxidative stress markers assayed were observed in rats exposed to gasoline fume. Significant reductions (p < 0.05) in sperm count and percentage motility in the exposed rats were observed. Significant (p < 0.05) increased in abnormal sperm cells characterized by damaged head, bent tail, damaged tail, and without head were also observed in the exposed rats. Histopathologically, severe degenerative testicular architectural lesions characterized by alterations in all the generations of sperm cells and reduction of interstitial cells were seen in the exposed rats. Gasoline fume is thus said to interfere with spermatogenesis and impair fertility in male gonad.

The contamination level of 12 antibiotics in 8 species of fish and shrimp from the Dongting Lake, China, was firstly studied. In total, the concentrations of antibiotics in fish and shrimp were lower, which were far lower than the maximum residue limits. The most abundant compound was enrofloxacin followed by sulfadiazine, sulfamethoxazole, sarafloxacin, and sulfadimidine with the highest content from 0.37 to 1.06 ng g⁻¹. The concentrations in Silurus asotus, Cyprinus carpio, and Palinuridae were higher. Concentrations in fish and shrimp from different water layers showed spatial difference, with the order of benthos and middle-lower species > middle-upper species. In addition, the antibiotic content could be affected by the diet, which showed the concentration level of antibiotics decreased in the order of carnivorous > omnivorous > phytophagous species. Human health risk assessment based on potential fish consumption indicates that main antibiotic risk factors were enrofloxacin and sarafloxacin, and main risk species were Silurus asotus and Palinuridae. The daily risk quotient of these antibiotics to rural residents was lower than townsmen. This study is the first report of antibiotic content in fish and shrimp from the Dongting Lake, which could enrich the research of emerging pollutants in aquatic products.

In this research, the optimum growth conditions for two zinc solubilizing bacteria (ZSB) have been studied for their potential application as bioinoculants to overcome Zn unavailability in soils. For this purpose, a laboratory-scale experiment was carried out to evaluate the zinc solubilizing ability of 80 plant growth promoting bacteria (PGPB) strains isolated from the rhizosphere of barley and tomato plants. To select effective ZSB, isolates were evaluated on Tris-mineral medium supplemented separately with zinc oxide, zinc carbonate, and zinc phosphate at a concentration of 0.1%. Two strains (Agrobacterium tumefaciens and Rhizobium sp.) were selected, based on a clear halo zone around their colonies in the solid medium supplemented with zinc oxide after 10 days of incubation at 29 °C. Results of solubilization at different pH values showed that these strains had solubilization activity in the range of pH 8–10 while no solubilization was observed at pH 6 and 7. The maximum Zn solubilization values were noted at pH 9: 51.4 mg L⁻¹ (Agrobacterium tumefaciens) and 72.1 mg L⁻¹ (Rhizobium sp). According to findings, bacterial growth was affected by different NaCl concentrations under in vitro condition. The salt concentration required for 50% inhibition of absorbance was 2.11 and 2.27% NaCl for Agrobacterium tumefaciens and Rhizobium sp., respectively. The maximum bacterial growth was observed at about 0.8% NaCl concentration.

This work found that the removal of chromium by a straw-derived biochar was significantly promoted or inhibited by various surfactants. For example, the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) inhibited the removal of Cr(VI) by the biochar but significantly promoted the removal of Cr(III) by the biochar. The nonionic surfactant Triton X-100 (TX-100) promoted the removal of Cr(VI) at low concentrations (< 100 mg L⁻¹) but inhibited the removal at high concentrations. Different mechanisms were found for the two surfactants. As an anionic surfactant, surface-sorbed SDBS changed the surface functional groups of the biochar, making the biochar negative charged and changing the sorption ability of the biochar. For the nonionic TX-100, monomers and micelles in the aqueous phase had a major influence on the sorption of chromium due to the impact on the interfacial tension between the biochar and the solution phase as well as the solution pH. The results suggest that when biochar is used to treat heavy metal wastewater containing coexisting surfactants, the type and concentration of surfactants must be considered as important factors. Under certain surfactant conditions, biochar will enable the simultaneous and efficient removal of heavy metals and surfactants.

Constant exposure of the living ecosystems to heavy metals, like cadmium (Cd), induces a detectable change at the biochemical and genetic level. Repeated application of phosphate fertilizers in paddy fields, leads to increase in Cd content of soil. Cd being highly mobile is transported to shoot and grain, thereby entering into the food chain of animal system. In the present study, treatment of 7-day old rice seedlings with 10 μM cadmium chloride resulted in Cd toxicity across the seven non-aromatic and six aromatic rice cultivars and landraces used for the study. Free proline and malondialdehyde content of treated samples were higher in comparison to the untreated samples, which indicated Cd induced tissue damage in plants. Photosynthetic pigment content of treated samples was also found to be much lower in comparison to the untreated samples, which is probably due to peroxidation of membrane, leading to compromised and lower photosynthetic efficiency of treated plants. At the genetic level, Randomly Amplified Polymorphic DNA assay was found to efficiently detect the genetic polymorphisms (caused by alterations in DNA bases) induced by Cd. Production of unique polymorphic bands in Cd-treated plants helps in assessment of the degree of damage Cd imparts on the plant system. Cluster analysis was performed and the rice genotypes were grouped into five distinct clusters, with IR64 and Tulsibhog in two distinct groups. Based on the variability in responses, the 13 rice genotypes were grouped into sensitive and tolerant ones.

Herein, biochar derived from lotus seedpods, as an effective adsorbent, was prepared by pyrolysis method at 300 and 600 °C. The physicochemical characteristics and cadmium adsorption properties were studied systematically by batch adsorption experiments, FTIR, SEM–EDX, XRD, and XPS. Cd adsorption onto lotus seedpod-derived biochar was better fitted using Freundlich isotherm and pseudo-second-order model. Adsorption capacity of biochar produced at 300 and 600 °C was 31.69 and 51.18 mg g⁻¹, respectively. The Cd adsorption capacity of biochar was related to its characteristics determined by pyrolysis temperature, including carbonization, surface area, surface morphology, and surface functional groups. Cd adsorption on lotus seedpod-derived biochar revealed that adsorption was controlled by multiple mechanisms including surface complexation, ion exchange, surface precipitation, and Cd–π interaction. This study showed that lotus seedpod-derived biochar is an effective and environmentally friendly adsorbent for water treatment.

Adhesively bonded polypyrrole thin films doped with benzene sulfonic acid (BSA) were electrodeposited on aminobenzenediazonium-modified flexible ITO electrodes and further employed for the detection of Pb²⁺, Cu²⁺, and Cd²⁺ metal ions in aqueous medium. The aminophenyl (AP) adhesive layer was grafted to ITO by electroreduction of the in situ generated parent diazonium compound. Polypyrrole (PPy) thin films exhibited remarkable adhesion to aminophenyl (ITO-AP). The strongly adherent polypyrrole films exhibited excellent electroactivity in the doped state with BSA which itself served to chelate the metal ions in aqueous medium. The surface of the resulting, modified flexible electrode was characterized by XPS, SEM, and electrochemical methods. The ITO-AP-PPy electrodes were then used for the simultaneous detection of Cu²⁺, Cd²⁺, and Pb²⁺ by differential pulse voltammetry (DPV). The detection limits were 11.1, 8.95, and 0.99 nM for Cu²⁺, Cd²⁺, and Pb²⁺, respectively. In addition, the modified electrodes displayed a good reproducibility, making them suitable for the determination of heavy metals in real wastewater samples.