Calix[4]arene-crown-6 compounds are promising ligands in the removal of cesium. With this aim, a macrocyclic compound, calix[4]arene-crown-6, was chemically immobilized onto inorganic ordered mesoporous carbon material. Several adsorption parameters such as nitric acid concentration, contact time, initial cesium content, operation temperature, and competing ions were studied. The results demonstrated the prepared material conserved high cesium selectivity of calix[4]arene-crown-6 and physicochemistry stability of the ordered mesoporous carbon matrix and showed the superior cesium adsorption performance. The optimum adsorption acidity determined as 3.0 M nitric acid was consistent with the actual acidity value in the back-end of the nuclear fuel cycle. The Langmuir model indicated the monolayer coverage adsorption and the highest mass adsorption capacity was calculated as 128.06 mg cesium/g. The pseudo-second-order model and D-R model proved the adsorption was a chemical process. Thermodynamics parameters showed the adsorption was spontaneous and exothermal in nature. Competing ions hardly affected cesium adsorption. Furthermore, the adsorbent showed almost intact adsorption capacity after five adsorption-elution cycles. The comprehensive performance highlights the composite material as a promising adsorbent for cesium adsorption from wastewaters. Graphical Abstract

Adsorption has been researched attempting to minimize the pollution caused by dyes, which represents a serious environmental problem as contamination of surface and ground water. Therefore, cellulose and its modified forms with amine and thiols groups constitute a class of versatile adsorbents for the removal of anionic dyes in aqueous solution. In this context, this work reports the preparation of cellulose modified by ethylene sulfide and ethylenediamine (Cel-ESEN), through the reaction of the cellulose modified by ethylene sulfide (CEL-ES) and ethylenediamine (EN). Materials were characterized by elemental analysis, which showed in the Cel-ESEN matrix 10.12 ± 0.10%, 5.52 ± 0.06% of sulfur and nitrogen, respectively. Nuclear magnetic resonance in the solid state of ¹³C (¹³C NMR) showed, for the Cel-ESEN matrix, a peak related to CH₂ groups from the molecules incorporated in the cellulose biopolymer. Crystalline Index obtained by X-ray diffraction (XRD) was in the order pure Cellulose > Cel-Cl > Cel-ES > Cel-ESEN. The adsorbent matrix (Cel-ESEN) was used in the removal of the remazol yellow GR (RY) dye in aqueous medium. Data obtained experimentally from kinetic study had the best adjustment to the proposed pseudo-second-order model. The adsorption process occurs in monolayer, is endothermic and thermodynamically favorable. Adsorption capacity of the modified material became 118 times higher than the starting material. These results suggest that the obtained biopolymer can be used as an alternative material to remove RY in aqueous solution.

Accurate estimation of extinction depth of shallow groundwater (EDSG) and identification of its influence factors are important for sustainable management of groundwater resources, ecological protection, and human health in intensively irrigated region. In this study, the ratio of actual groundwater depth and EDSG (RAE) method was used to understand the spatial variability of EDSG in the Sanjiang Plain, one of China’s largest grain production bases and China’s largest inland freshwater wetland region. The study showed a large spatial variation of EDSG in the region. Spatially, the sites, which were in the northeast and center had the deepest and the shallowest EDSG, whereby, indicate that it has higher and lower pumping potential capacity. Many factors including climate, soil parameters, vegetation and topography affected the EDSG. We also identified an area of 3.86 × 10¹⁰ m², which accounting for 35.3% of the entire Sanjiang Plain, has exceeded the ESGD by over exploited for years. Knowledge of the variation and influence factors of EDSG for a certain plant system and the current shallow groundwater condition in the higher latitude region can be a key to the development of preventive actions for large quantity pumping groundwater and protection regional and sustainable development of irrigated agriculture.

Fats, oils, and grease (FOG) and source separated organics (SSO) were treated with the microwave-enhanced advanced oxidation process (MW-AOP) at 90 and 110 °C, with varying amounts of hydrogen peroxide dosages. The treatment efficiency, in terms of soluble substrates and volatile fatty acids (VFA), increased with an increase in both temperature hydrogen peroxide dosages. Fatty acids and compounds with carbonyl group and/or hydroxyl group in both initial and treated FOG samples were identified by gas chromatography-mass spectrometry. MW-AOP treatment temperatures and hydrogen peroxide dosages dictated the formation of degradation products. The degradation followed peroxidation mechanism to produce lower molecular weight substrates such as short chain fatty acids which would be less inhibitory to microbes. After the MW-AOP treatment, both SSO and FOG comprised of more soluble and low molecular weight compounds. These compounds included VFA and nutrients that would be readily available for bacterial or plant uptake.

Transverse mixing is a complex process and important in understanding the transport of pollution in rivers. This study presents a genetic programming (GP)-based model for estimating the transverse mixing coefficient (TMC) in flumes and rivers. More than a hundred of data points from previous studies, including datasets on laboratory straight rectangular flumes and field measurements in natural rivers, are collected and used to develop the final formulae for estimating TMC. During the analysis, TMC is separated into the transverse turbulent diffusion coefficient and the transverse dispersion coefficient given that they represent two different processes. Before formula optimization and search are performed using GP software, the target formulae are semi-defined to reduce search time and ensure the physical basement of the final formulae. The model presented in this study exhibits good improvement in terms of accuracy and physical meaning compared with existing equations.

Fipronil has been associated with neurotoxicity, carcinogenicity, endocrine disruption, persistence in soil, and low uptake by plants and is a potential groundwater contaminant. Fipronil degradation by silver nanoparticles (AgNPs) from medicinal plant extracts was investigated in spiked water. Also, remediation capacity of soil contaminated by fipronil under the combined application of green AgNPs and phytoremediation was investigated. Brassica-AgNps, Ipomoea-AgNps, Camellia-AgNps, and Plantago-AgNps in water solution significantly reduced fipronil residues by 95.45, 90.15, 63.65, and 63.48%) during 2 days of treatment as compared with 18.42% in untreated water without AgNps. Fipronil amide and fipronil-desulfenyl metabolites were detected in water under the influence of AgNps. The contribution of Brassica-AgNps, Plantago-AgNps, Ipomoea-AgNps, and Camellia-AgNps to the dissipation of fipronil in the soil were 68.8, 54.64, 43.75, and 30.99%, respectively, compared with 10.14% by Plantago major alone through 6 days. Low uptake and translocation of fipronil by P. major roots and leaves were seen in flooded soil alone or under the influence of AgNps within 6 days of treatment. However, the resulting fipronil amide product accumulates in large quantities in P. major roots and leaves. These results show that AgNps and P. major play a major role for the remediation of fipronil contaminated water and in flooded soil, while P. major played an important role for remediation the polar break product, fipronil-amide as phytoremediation.

The objectives of this study were to investigate whether sedimentary iron can promote the growth of cyanobacteria and determine the effects of different forms of iron on cyanobacterial growth. In this study, we simulated cyanobacterial growth in a eutrophic freshwater lake under Fe-deficient conditions using three systems containing artificial lake water and algae (the WA system); artificial lake water and sediment (WS system); and artificial lake water, sediment and algae (the WSA system). Results demonstrate that Fe from sediments did facilitate cyanobacterial growth. Sequential Fe extractions revealed that the majority of sedimentary iron was in the form of reactive iron (80.63%). Furthermore, cellular iron from cyanobacteria and water-soluble Fe in sediments had a strong and significant negative correlation (− 0.792, P < 0.01), indicating that water-soluble Fe in sediments is the most important form of iron for influencing cyanobacterial growth. Further studies on water-soluble Fe mobility showed that up to 47.5% of the released water-soluble Fe could be absorbed into cyanobacterial cells, thereby indicating that water-soluble Fe is significant for cyanobacterial growth and serves as a critical Fe source when lake water iron is limited. In addition, the study found that easily reducible Fe oxide minerals have the largest release potential. These findings provide new insights that could improve management of cyanobacterial blooms.

In this study, a mesoporous chromium-functionalized γ-Al₂O₃ (Cr/γ-Al₂O₃) catalyst was prepared by an impregnation method, and the catalytic activity was evaluated by the degradation of organics wastewater. The prepared catalyst was characterized by X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption-desorption experiments, and scanning electron microscopy. The characterization results confirmed that the pores in the Cr/γ-Al₂O₃ catalyst distributed broadly in the mesoporous region, and the active chromium species were highly dispersed on the catalyst surface. The catalytic activity tests showed that the Cr/γ-Al₂O₃ catalyst exhibited a superior performance for the degradation of organics wastewater with H₂O₂ assistance. And the methylene blue (MB) disappeared within 20 min and the COD removal reached 76.5% within 40 min for the MB-simulated wastewater; for the phenol-simulated wastewater, the phenol removal was above 95% and the corresponding COD removal reached 71% within 40 min. Such an excellent catalytic performance demonstrates that the Cr/γ-Al₂O₃ catalyst has a potential application in the degradation of complex organics wastewater simultaneously.

Coastal saline rice fields play an increasingly important role in rice production and associated greenhouse gas (GHG) emissions. However, few studies investigated the influences of nitrogen (N) fertilizer and soil ameliorant on GHG emissions simultaneously in this region. Thus, a field experiment was established to study the effects of different N fertilizers and soil ameliorant on global warming potential (GWP) and yield-scaled GHG intensity (GHGI) after accounting for carbon dioxide (CO₂) equivalent emissions of methane (CH₄) and nitrous oxide (N₂O), agrochemical inputs, and farm operations along with agronomic nitrogen use efficiency (NUE) during the rice season of 2016 in a coastal saline paddy in Lianyungang, China. The experiment was initiated with four N treatments (N0, no N; Nu, urea; Nm, organic-inorganic mixed fertilizer; Nw, organic fertilizer made from wheat straw) and two ameliorant (A) treatments (A0, no ameliorant; A1, 22.5 kg ha⁻¹ ameliorant). The results showed that three N fertilizers significantly increased the CH₄ emissions, N₂O emissions, GWP, and grain yield by 42.2% (p < 0.001), 57.1% (p < 0.001), 49.8% (p < 0.001), and 58.9% (p < 0.001), respectively. NuA1, NmA1, and NwA1 treatments obviously reduced the yield-scaled GHGI by 21.3%, 16.3%, and 12.4%, respectively, relative to the corresponding NuA0, NmA0, and NwA0 treatments. Overall, although three N fertilizers would increase the GWP, combining an ameliorant amendment with N fertilizer can effectively reduce the yield-scaled GHGI and meanwhile increase the grain yield, particularly the NmA1 strategy.

The potential to remove methylene blue (MB) basic dye and indigo carmine (IC) acidic dye, from wastewater treatment systems using corn stigmata through biosorption was investigated in batch experiments. The effects of contact time, solution pH, biosorbent dosage, initial dye concentration, salts, and temperature were sought. Results showed that the maximal uptakes of MB were 106.3 mg g⁻¹ at pH = 7 and 63.7 mg g⁻¹ for IC at pH = 2. In order to determine the properties and surface structure of the biomass physicochemical properties (pHₚzc, elemental analysis, Boehm’s titration, and chemical composition), spectral (FTIR analysis) and morphological characteristics (SEM) were investigated. Random distribution of the active sites was described by the new biosorption fractal model of Brouers–Sotolongo. The thermodynamic study demonstrated the favorable character of the biosorption of MB and of IC, which was inhibited by the presence of salts. The elucidation of the biosorption mechanism showed that the biosorption of MB onto corn stigmata was mainly controlled by chemisorption and the biosorption of IC was described by physisorption.