Nano-structured zinc sulfide (Nano-ZnS) has been demonstrated to be a promising alternative to activated carbon (AC) for controlling mercury emission from coal combustion flue gas. The ultimate fate of the mercury-laden Nano-ZnS after mercury capture is mostly disposed in landfill with fly ashes. Thus, the stability of mercury adsorbed on the Nano-ZnS is of considerable significance in the secured disposal of fly ash after mercury removal and in the commercial application of the Nano-ZnS sorbent for removal of mercury from coal combustion flue gas. In this work, a modified toxicity characteristic leaching procedure (TCLP) was conducted to evaluate the leachability of mercury on the Nano-ZnS. The effects of leachate pH value, leaching time, liquid-to-solid ratio, and acid rain types on mercury leaching from the mercury-laden Nano-ZnS were systematically investigated. The TCLP results show that the concentration of mercury in leachate was far below the safe limit (200 μg/L) as imposed by the US Environmental Protection Agency (EPA) for classifying a material as a hazardous waste. All the key parameters that generally affected metal leaching rate exhibited slight effect on mercury leaching from the mercury-laden Nano-ZnS. Leaching tests at various highly severe conditions resulted in less than 0.01% mercury leaching from the mercury-laden Nano-ZnS. Sequential selective extraction tests demonstrated that mercury sulfide (HgS) was the dominant adsorption product on the Nano-ZnS, which guaranteed the excellent stability of mercury adsorbed on the Nano-ZnS. Graphic abstract ᅟ

Phenol is toxic to human and persistent in the environment. Traditional treatment methods have the disadvantages of long treatment time, large amount of agents, and secondary pollution. In this study, a novel gas-liquid two-phase dielectric barrier discharge reactor was designed to remove phenol in aqueous solution. The effects of operating conditions (applied voltage, discharge spacing, pH, and conductivity), different water matrix (deionized water, groundwater, surface water, tap water), and inorganic ions were investigated. Moreover, the reaction mechanisms and the possible degradation pathway were proposed. The removal efficiency of phenol achieved 95.5% under the optimal operating conditions (discharge voltage of 17.6 kV, discharge gap of 1 mm, air flow rate of 60 mL min⁻¹) coupling with H₂O₂ at 10 mM. The presence of different concentrations of inorganic ions (0.1, 1, 10, and 20 mM) could inhibit the phenol removal efficiencies. Specially, Cl⁻ had different effects on phenol removal efficiency. The inhibition of Cl⁻ on phenol removal was weakened when Cl⁻ concentration was greater than 1 mM, which allows the technology that has certain advantages in treating high-salt wastewater containing high chloride concentration. In addition, ˙OH was verified as the main active species in phenol removal. The possible degradation pathway was proposed according to theoretical calculation and GC-MS measurement.

ZnO nanoparticles (NPs) are applied in a wide variety of applications and frequently accumulate in the environment, thus posing risks to the environment and human health. Arbuscular mycorrhizal (AM) fungi (AMF) associate symbiotically with roots of most higher plants, helping their host plants acquire phosphorus (P). AMF can reduce the toxicity of ZnO NPs, but the benefits of AMF to host plants highly vary with soil available P. We hypothesize that organic P may help AMF to alleviate ZnO NP phytotoxicity. Here, we investigated the effects of inoculation with Funneliformis mosseae on plant growth and Zn accumulation, using maize grown in soil-sand mix substrates spiked with ZnO NPs (0 or 500 mg kg⁻¹) under different organic P supply levels (0, 20, or 50 mg kg⁻¹). The results showed addition of ZnO NPs inhibited root colonization rate, increased the shoot/root P concentration ratio, and led to significant Zn accumulation in soil and plants. As predicted, AM effects on maize plants all varied with P supply levels, both with or without ZnO NP additions. Organic P interacted synergistically with AMF to promote plant growth and acquisition of P, N, K, Fe, and Cu. AM inoculation reduced the bioavailable Zn released from ZnO NPs and decreased the concentrations and translocation of Zn to maize shoots. In conclusion, ZnO NPs caused excess Zn in soil and plants, posing potential environmental risks. However, our present results first demonstrate that organic P exhibited similar positive effects to AMF and interacted synergistically with AMF to improve plant growth and nutrition, and to decrease Zn accumulation and partitioning in plants, and thus helped diminish the adverse effects induced by ZnO NPs.

We previously reported that a simple treatment—addition of only small amounts of water to coal fly ash (CFA) to form CFA paste followed by aging for 1–4 weeks—is advantageous for the immobilization of highly soluble B, F, Cr, and As. In this study, we investigated the leachability of Ca, SO₄, B, and As over time from non-aged and aged CFA samples to elucidate a possible immobilization mechanism. For this purpose, two types of CFA samples, one showing effective immobilization of B and As by water addition and aging (sample A) and the other showing less or no immobilization (sample B), were examined. Calcium and SO₄, B, and As in non-aged sample A dissolved immediately after the start of the leaching test, indicating that these elements existed in highly soluble particles. After the rapid dissolution, their concentrations in the leachate gradually increased, possibly due to the dissolution of glassy phases. During the 1-week leaching test, the B and As concentrations in the leachate finally decreased. The addition of only small amounts of water to CFA (Sample A) for aging produce both alkaline and supersaturation conditions for the formation of several types of Ca-bearing secondary minerals such as calcite and ettringite, which are formed under alkaline conditions. Boron and As originally existing as highly soluble particles in CFA are expected to be incorporated into and/or sorbed on these secondary minerals as water-insoluble phases. Compared to non-aged CFA, their leachability from the aged sample A remained lower throughout the entire leaching test. Possibly due to these secondary minerals being formed on the CFA surface, B and As dissolutions associated with glassy phases are also prevented. In contrast, the pH of the leachate from CFA (sample B) at the beginning of the leaching test was acidic and then abruptly became alkaline. This means that water-soluble particles that can produce acidic conditions are also contained in these alkaline CFAs. Dissolution of these substances during aging makes it difficult to generate alkaline conditions in the CFA paste. Consequently, the formation of secondary minerals and the concomitant immobilization of toxic elements are prevented.

In this study, different nitrogen doses (0, 16, 48, 64, 80, and 96 kg ha⁻¹) from two sources, biofertilizer (from anaerobic digestion of cattle wastewater) and urea, were applied to cultivate two sugarcane varieties (RB 867515 and SP 803280). °Brix values higher than 21% were obtained with application of 80 kg ha⁻¹ from biofertilizer. The mean productivity of the cultivar RB 867515 using biofertilizer was 147.5 ton ha⁻¹, while from urea it was 136.87 ton ha⁻¹. The cultivar SP 803280 produced an average yield of 152.25 ton ha⁻¹ when applying biofertilizer and 154.37 ton ha⁻¹ with use of urea. Significant differences (P ≤ 0.05) between the use of biofertilizer and urea were detected for cultivar RB 867515 in terms of crude protein concentration. The application of 80 kg of N ha⁻¹ was considered the ideal dose, corresponding to fertirrigation blades of 54 mm of biofertilizer. The experiment showed that the biofertilizer formulation analyzed can replace urea as a nitrogen source for growing sugarcane. Graphical Abstract ᅟ

The influence of sulfonation of both macroporous and hyper-cross-linked polystyrenic polymers on their adsorption capacity for SO₂ removal from residual gases was studied through equilibrium experiments and microstructural analysis. The results showed that the insertion of functional sulfonic active groups leads to a decrease of adsorption capacity of macroporous and macronet resins mainly due to decreasing of specific surface area of the resins. The results were compared with those obtained for powdered activated carbon, which has an adsorption capacity higher compared with that of macroporous resins and lower than those of macronet resins. The high adsorption capacity of macronet resins has been attributed to the advanced cross-linking of the polystyrene chains that leads to the formation of a three-dimensional network with a high specific surface area. The fitting of the experimental data on the typical adsorption isotherms (Langmuir and Freundlich) highlighted the surface heterogeneity of macroporous and macronet resins.

Salt-affected soils cover a wide area, limiting agricultural production worldwide. Several remediation options are available and include chemical and vegetative remediation, but several aspects of each process are not yet fully understood. Therefore, the goal of this work was to study the application of both techniques in a highly saline scenario and provide insights into the limits of the application of this technology. Two chemical amendments (CaSO₄ and CaCl₂) and two plant species (Juncus maritimus Lam. and Spartina maritima (Curtis) Fernald) were tested to remediate a non-calcareous soil with an electrical conductivity of 20 dS m⁻¹ (EC) and a sodium adsorption ratio (SAR) of 45. Vegetative bioremediation experiments were performed under non-leaching conditions. As such, salts were redistributed and increased at the surface and decreased in depth due to capillary rise. In such conditions, there was no clear positive effect of plants on soil parameters. However, tested plants grew, accumulated, and excreted salts and sodium comparably to other research in the literature. Regardless, the obtained results suggest that plant salt uptake alone may not be sufficient for soil remediation, and therefore, other mechanisms may also play a significant role. As to chemical amendments, both chemicals used proved to be effective and reduced non-calcareous saline soil parameters to below threshold values of 4 dS m⁻¹ for EC and 7 for SAR. However, CaCl₂ was more effective and faster to remediate than CaSO₄, likely due to higher solubility. Therefore, CaCl₂ may be a viable, yet less tested, option for faster remediation processes.

Nanotechnology is a dynamically developing field of scientific and industrial interest across the entire world, and the commercialization of nanoparticles (NPs) is rapidly expanding. Incorporation of nanotechnologies into a range of manufactured goods results in increasing concern regarding the subsequent release of engineered NPs into the environment. One of the biggest threats of using NPs is the transfer and magnification of these particles in the trophic chain. The aim of the studies was the evaluation of the distribution of TiO₂ NP contamination in the aquatic ecosystem under laboratory conditions. Bioaccumulation of TiO₂ NPs by plants (Elodea canadensis) and fish (Danio rerio) in the source of contamination was investigated. The studies were focused on the consequences of short-term water contamination with TiO₂ NPs and the secondary contamination of the components of the investigated model ecosystem (plants, sediments). It was found that in the fish and the plants exposed to NP contamination, the amount of Ti was higher than in the control, indicating an effective bioaccumulation of NPs or ions originating from NPs. It was clearly shown that the NPs present in the sediments are available to plants and fish. Additionally, the aquatic plants, an important trophic level in the food chain, can accumulate NPs and be a source of NPs for higher organisms. It was concluded that even an incidental contamination of water by NPs may result in long-term consequences induced by the release of NPs.

Membrane bioreactor (MBR) and microbial fuel cell (MFC) are new technologies based on microbial process. MBR takes separation process as the core to achieve the high efficient separation and enrichment the beneficiation of microbes during the biological treatment. MFC is a novel technology based on electrochemical process to realize the mutual conversion between biomass energy and electric energy, in order to solve the problems of serious membrane fouling and low efficiency of denitrification in membrane bioreactor, the low power generation efficiency, and unavailability of bioelectric energy of MFC. In recent years, MFC-MBR coupling system emerged. It can effectively mitigate the membrane fouling and reduce the excess sludge production. Simultaneously, the electricity can be used effectively. The new coupling system has good prospects for development. In this paper, we summarized the research progresses of the two kinds of coupling systems in recent years and analyzed the coupling structure and forms. Based on the above, the future development fields of the MFC-MBR coupling system were prospected.

In this study, the performance of oxidation with actived persulfate (PS) by graphene oxide-TiO₂ nanosheet (GO-TiO₂) was investigated for diclofenac (DCF) removal, an anti-inflammatory analgesic being widely used in human health care and veterinary treatment. GO-TiO₂ containing oxygen functional groups is employed as an activator for the activation of PS used as the oxidizing agent. Modeling and optimization of the process were performed by central composite design (CCD) as a response surface methodology (RSM). The effects of various factors, including PS concentration, GO-TiO₂ amount, initial pH of DCF solution, and reaction time on DCF oxidation, were evaluated. When the estimated values of the full quadratic model obtained with CCD were compared with the actual experimental results, a strong agreement was obtained with an R² value of 0.9553. Besides, the model consistency was verified by analysis of variance (ANOVA) with a value of 20.17 of F value and P value of less than 0.05. After the optimization run, maximum DCF removal of 93.06% occurred with contact time of 14 min, pH of 5.54, PS concentration of 10 g/L, and 0.1 g of GO-TiO₂ as optimal variable values.