The linkage between financial development and energy consumption is widely investigated in the literature. However, the non-linear relationship between financial development and energy demand is still under debate. Therefore, this study aims to examine the non-linear relationship between financial development, economic growth, and energy consumption in OECD countries. The study uses the Driscoll–Kraay standard errors panel regression model for spanning from 1980 to 2016. The empirical findings indicate that an inverted U-shape relationship exists between financial development and energy consumption as well as between economic growth and energy consumption. Moreover, the feedback hypothesis is found between financial development and energy use. Additionally, income and energy use granger cause each other. The innovative findings contribute to extant literature, which is of special interest to the country’s policymakers regarding energy efficiency.

In order to control bacterial adhesion and metal corrosion in the circulating cooling water system, it is necessary to prepare a nanocomposite-modified coating with antibacterial and anticorrosive functions. Copper and zinc composite oxide (CuZnO) was synthesized to prepare CuZnO@RGO nanocomposites. The antibacterial mechanism of CuZnO@RGO nanocomposites was investigated using gram-negative bacteria E. coli and gram-positive bacteria S. aureus as the two model microorganisms. The antibacterial properties of CuZnO@RGO nanocomposites on mixed bacteria were researched in the cooling water system. In addition, the CuZnO@RGO waterborne polyurethane (WPU) composite coating (CuZnO@RGO/WPU) was synthesized. The antibacterial performance, hardness, and corrosion inhibition performance of CuZnO@RGO/WPU composite coating in the cooling water system were also investigated. The results showed that after adding CuZnO@RGO nanocomposites to E. coli or S. aureus suspension, the protein leakage after 20 h was 9.3 times or 7.2 times higher than that in the blank experiment. The antibacterial rate of CuZnO@RGO nanocomposites in circulating cooling water reached 99.70% when the mass fraction of RGO was 15%. When the mass fraction of CuZnO@RGO accounting for CuZnO@RGO/WPU composite coating was 2%, the antibacterial rate, hardness, and corrosion inhibition efficiency were 94.35%, 5H, and 93.30%, respectively.

The increase of salt concentrations in influent wastewaters will be a consequence of the sea level rises in coastal areas due to climate change and the future use of seawater to flush toilets as a cost-attractive option for alternative water resources. Yet, little is known about the salinity effect on full-scale wastewater treatment plants (WWTPs) performance and on greenhouse gas (GHG) emissions, such as nitrous oxide (N₂O). This study aimed at quantifying the N₂O emissions of a full-scale biological aerated filter (BAF) and to correlate the dynamic behavior of the emissions with the process conditions and the periods of infiltration of seawater. A full-scale BAF was monitored for 3 months to assess both their gaseous and liquid N₂O fluxes. The total average daily N₂O emissions of the plant were 6.16 g N–N₂O/kg of NH₄–N removed. For the first time at full-scale, a correlation between the N₂O emissions and the wastewater influent conductivity (salinity) was found, in which the increase in seawater infiltration in the sewer at high tide augments the daily N₂O production and emission to 13.78 g N–N₂O/kg of NH₄–N removed. The proportional increase in influent conductivity and the N₂O emission factor in this WWTP suggested that periods of high conductivity could serve as an indicator of increased N₂O emissions by the plant. Furthermore, the operational conditions and the wastewater influent characteristics that influence the N₂O emissions were identified as being the dissolved oxygen (DO) dynamics due to the filter washing steps, leading to rapid transitions from oxic to sub-oxic conditions, as well as the (re-)adaptation of microbial consortia due to the dynamics of the biofilm thickness associated to the daily washing process. This study shows the impact that the washing process and seawater infiltration has on the N₂O emissions of a BAF and contributes to a better understanding of the operational conditions impacting the emissions in WWTPs.

The discharge of organic dye into environment is the threat to hydrosphere and biosphere. On the other hands, the agriculture solid wastes such walnut and almond shells pose serious pollutions in lithosphere and atmosphere when burned. The aim of present investigation is to fabricate microporous activated carbon from agriculture waste shells by microwave irradiation as efficient adsorbent to overcome these problems. Firstly, zinc chloride was impregnated into milled shell particles, 300 μm, by conventional and microwave-assisted techniques and then the dry precursors were heated in the closed and open ceramic vessels in air and nitrogen atmospheres. The experimental investigation was carried out to understand the roles of different fabrication factors such as shell particle size, catalyst impregnation ratio, microwave power, carbonization temperature, and atmosphere on cationic dye removal from wastewater. The mentioned factors efficiently affect the dye removal onto obtained activated carbon. The increase in the microwave power up to 600 W could effectively increase the dye removal. However, the higher powers inversely affect the removal efficiency. The equilibrium data were well fitted by Langmuir equation with high linear regression coefficients in which the maximum adsorption capacities of activated carbon produced by walnut and almond shells were determined to be 98 and 114 mg/g, respectively. The most prominent advantage of activated carbon produced from almond shell is lower content of catalyst employed in impregnation stage. Although the larger particles of solid waste were applied, the spongy nature with average pore diameter of 2.4 nm is the unique characteristic of activated carbon fabricated from almond shell which improves the performance of adsorbent in wastewater treatment.

Arsenic (As) is the most hazardous soil contaminant, which inactivates metabolic enzymes and restrains plant growth. To withstand As stress conditions, use of some alleviative tools, such as arbuscular mycorrhizal (AM) fungi and silicon (Si), has gained importance. Therefore, the present study evaluated comparative and interactive effects of Si and arbuscular mycorrhiza-Rhizophagus irregularis on phytotoxicity of arsenate (As V) and arsenite (As III) on plant growth, ROS generation, and antioxidant defense responses in pigeonpea genotypes (Tolerant-Pusa 2002; Sensitive-Pusa 991). Roots of As III treated plants accumulated significantly higher total As than As V supplemented plants, more in Pusa 991 than Pusa 2002, which corresponded to proportionately decreased plant growth, root to biomass ratio, and oxidative burst. Although Si nutrition and AM inoculations improved plant growth by significantly reducing As uptake and the resultant oxidative burst, AM was relatively more efficient in upregulating enzymatic and non-enzymatic antioxidant defense responses as well as ascorbate–glutathione pathway when compared with Si. Pusa 2002 was more receptive to Si nourishment due to its ability to establish more efficient mycorrhizal symbiosis, which led to higher Si uptake and lower As concentrations. Moreover, +Si+AM bestowed better metalloid resistance by further reducing ROS and strengthening antioxidants. Results demonstrated that the genotype with more efficient AM symbiosis in As-contaminated soils could accrue higher benefits of Si fertilization in terms of metalloid tolerance in pigeonpea.

The aim of the study was the biomonitoring of the chronic exposure to Pb by measuring its levels in blood, urine, and hair of battery workers. Blood lead (BPb), urinary lead (UPb), hair lead (HPb), and urinary δ-aminolevulinic acid (UALA) levels were determined for 52 workers in a battery plant and compared to those of 20 non-occupational exposed subjects (controls). BPb and UPb levels were determined by graphite furnace atomic absorption spectrometry (GFAAS). HPb levels were measured by triple quadrupole ICP-MS and UALA levels were determined using cation exchanger column. The measured levels were significantly higher compared to the controls exceeding the OSHA cutoff values (p < 0.01). The GM mean levels of BPb, UPb, UALA, and HPb of workers were 715 μg L⁻¹, 331 μg L⁻¹, 16.3 mg g⁻¹, and 234 μg g⁻¹, respectively. The GM mean levels of BPb, UPb, UALA, and HPb of controls were 93.6 μg L⁻¹, 36.3 μg L⁻¹, 1.9 mg g⁻¹, and 1.8 μg g⁻¹, respectively. Significant correlations were observed between BPb and UALA (r = 0.630, p = 0.000), UPb and UALA (r = 0.566, p = 0.000), and between BPb and HPb (r = 0.466, p = 0.004). The significant correlation between BPb and HPb suggests the usefulness of hair for assessing occupational exposure particularly when the study area presents medium to high levels of Pb pollution. The association between Pb biomarkers and potential confounding factors revealed significant influence of the occupational factor over smoking and alcohol consumption. The results of this study urge for the reinforcement of the implemented engineering controls and safety measures in order to reduce exposure and to address the health issues related to Pb poisoning.

This study investigated the influence of membrane property and feed water organic matter quality on the permeate flux and water quality during gravity-driven membrane (GDM) filtration. GDM filtration was continuously carried out over 500 days at hydrostatic pressure of 65 mbar in dead-end mode without any back-flushing or membrane cleaning. Three ultrafiltration (UF) membranes (PES-100 kDa, PVDF-120 kDa, and PVDF-100 kDa) and one microfiltration (MF) membrane (PTFE-0.3 μm) were tested for treating lake water with varied organic matter qualities due to algal growth. The fluxes of the four membranes rapidly decreased to ~8 L/(m² × h) within a week of GDM filtration. The flux variations were quite similar for the four membranes during the entire GDM filtration, indicating that membrane property has a little effect on the flux. The flux strongly depends on the feed water organic matter quality. The average flux in treating low organics containing water (7–60 days) was ~5 L/(m² × h) and decreased to ~2 L/(m² × h) in treating high organics containing water (60–300 days). The accumulation of algal-derived biopolymers was mainly responsible for the flux decline by forming biofilms with high permeation resistance. The average flux in 300–500 days increased to ~3.5 L/(m² × h) when the feed water contained lower levels of biopolymers and higher levels of easily biodegradable organics, which created open and heterogeneous biofilms with lower permeation resistance. Removal efficiency for Escherichia coli was more than 5 log, while the removal efficiency for total bacterial cells was 1 log–2 log for the four membranes, indicating some bacterial regrowth after the filtration. Removal efficiency for the MS2 phage was 2.4 log and 1.5 log for the fouled PES-UF and PTFE-MF membranes.

The ability of a soil to sustain infiltration rates and to attenuate pollutants is critical for the design and operation of Managed Aquifer Recharge/Soil Aquifer Treatment and phyto-treatment schemes, also referred to as “Blue Infrastructures”. We investigated the buffering capacity of a sediment sample and a peat soil sample for nutrients and selected pharmaceutical compounds and its evolution under continuous infiltration of secondary treated wastewater (TWW) in column experiments. Samples were obtained from two blue infrastructures, the Sant’Alessio Induced River Bank Filtration plant and the San Niccolò large-scale phyto-treatment plant in Italy, and were mainly different in their organic carbon contents (0.9 and 48%, respectively). In the column experiments, a constant infiltration rate of about 0.5 L/d was maintained for 6 months. After 4 months of operation, diclofenac and carbamazepine were spiked into the TWW to evaluate their fate. Water quality was monitored by periodic water sampling from the column inflow, at sampling ports along the column length, and at the outflow. Hydraulic conductivity (K) was also monitored. The hydraulic conductivity of the Sant’Alessio sediment decreased by a factor of 10 during the first 10 days of infiltration and then stabilized, while for the San Niccolò K (initially lower) remained constant for 50 days until it decreased following a change of the redox condition in the column. The different redox conditions, due to the two different soils tested, influenced also the concentration and mobility of PO₄³⁻, Fe, Mn, and NPOC, and the speciation of the redox sensitive elements (nitrogen and sulfur). NOPC and phosphate were enriched during the filtration through San Niccolò peat soil (from 2 to 4 times, respectively), while they were buffered by the Sant’Alessio sediment (from 0.2 to 0.4 times, respectively). Diclofenac removal (69% and below 20% for San Niccolò and Sant’Alessio, respectively) was related to sorption and degradation processes and it was lower than the removal of carbamazepine in both soils (76 and 35%). The buffer capacity differences between the two soils were higher for diclofenac (62%) than carbamazepine (35%). Nevertheless, since no apparent degradation of carbamazepine was detected in both soils, its persistence in the soil may have a larger impact in case of desorption, posing contamination risk to groundwater. The results highlight the importance of the soils or sediments to be used as medium in such nature-based solutions for their operations. They also offer an approach to, e.g., tailor man-made soil layers in infiltration basins. We strongly suggest that soil characteristics and test duration are carefully considered in designing these infrastructures, when nature-based processes are the choice for dealing with reuse of treated wastewater management issues.

The use of alunite as an adsorbent for the removal of dye was the aim of this report. Mixing the alunite with different salts may allow adsorption with higher efficiency. In the present study, the thermal decomposition product of alunite-potassium chloride mixture (TDPA-KCl) was used efficiently and inexpensively to remove Reactive Blue 49 (RB49) dye. The adsorption capacity of TDPA-KCl was found to be affected by pH, temperature, adsorbent amount, calcination temperature, dye concentration, and ionic strength. The highest RB49 adsorption yield was obtained at an initial pH of 2 and an equilibrium was reached within 20 min using 80 mg of adsorbent. The most suitable kinetic model was found as the pseudo-second-order and compatible isotherm was determined as the Langmuir model. The optimum adsorption capacity was found as 119.10 mg g⁻¹ at 40 °C. ∆G°, ∆H°, and ∆S° values were calculated. A positive value of ∆H° stated that the adsorption is exothermic and spontaneous. In addition, ∆G° showed a more negative value when temperature was increased. Column studies indicated that TDPA-KCl could be effectively used for five cycles without any loss in its desorption potential. Breakthrough studies also supported a favorable adsorption of RB49 onto TDPA-KCl. This study showed that TDPA-KCl is a practical, efficient, and inexpensive adsorbent to remove reactive dyes from wastewater.

A novel magnetic attapulgite–biochar composite (MABC) derived from natural attapulgite, cauliflower leaves, and FeCl₃ was successfully prepared as a low-cost adsorbent for oxytetracycline (OTC) removal from aqueous solution. Characterization experiments by different techniques suggested that attapulgite clay particles and Fe₃O₄ nanoparticles were successfully covered on the MABC surface. Compared with the pristine biochar (CLB) and attapulgite–biochar composite (ABC), MABC had the largest surface area, well-developed pore structure, and more surface oxygen-containing functional groups which could interact with organic pollutant via hydrogen bonding, π–π electron coupling, complexation, and ion exchange. The maximum adsorption capacity of MABC by the Langmuir model was 33.31 mg/g, which was dramatically higher than that of CLB and ABC. The effects of solution initial pH had little difference on the adsorption of OTC because of the buffering effect. Adsorbent-regeneration studies of MABC exhibited good reusability and separation property. All the results indicated that MABC could be used as a potential adsorbent because of its easy preparation and separation, high efficiency, wide pH range application, and abundant and cheap raw materials in the global ecosystem. Graphical abstract