The aim of this study was to evaluate the performances of Pichia kudriavzevii CR-Y103 yeast strain for the decolorization, biodegradation, and detoxification of cationic dye C.I. Basic Blue 41, a toxic compound to aquatic life with long-lasting effects. Under optimized cultural conditions (10.0-g L⁻¹ glucose, 0.2-g L⁻¹ yeast extract, and 1.0-g L⁻¹ (NH₄)₂SO₄), the yeast strain was able to decolorize 97.86% of BB41 (50 mg L⁻¹) at pH 6 within 4 h of incubation at 30 °C under shaken conditions (12,238.00-μg h⁻¹ average decolorization rate) and 100% within 12 h. The UV-Vis spectral analysis, high-performance liquid chromatography (HPLC), and Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the complete decolorization and degradation of the BB41 dye by P. kudriavzevii CR-Y103. Also, other seven yeast strains, isolated from soil, as P. kudriavzevii (CR-Y108, CR-Y119, and CR-Y112), Candida tropicalis CR-Y128, Cyberlindnera saturnus CR-Y125, and Candida solani CR-Y124 have shown a promising decolorizing potential of azo-dye BB41 (99.89–76.09% decolorization). Phytotoxicity, cytotoxicity, and genotoxicity assays on Trifolium pratense and Triticum aestivum seedlings confirmed the high toxicity of BB41 dye (500 ppm), with inhibition on germination rate (%), root and shoot elongation, decreasing of mitoxic index value (with 34.03% in T. pratense and 40.25% in T. aestivum), and increasing the frequency of chromosomal aberrations (6.87 times in T. pratense and 6.25 times in T. aestivum), compared to control. The same biomarkers indicated the nontoxic nature of the BB41 degraded metabolite (500 ppm) obtained after P. kudriavzevii CR-Y103 treatment. Moreover, the healthy monkey kidney cells (Vero cells) had a low sensitivity to BB41 biodegraded products (250 μg mL⁻¹) (MTT cell viability assay) and revealed minor DNA damage (comet assay) compared to BB41 dye treatment. These findings show that P. kudriavzevii could be used in eco-friendly bioremediation technologies, applicable for reducing the toxicity of basic azo-dyes containing wastewaters.

Due to the lack of appropriate wastewater treatment facility in rural areas, the discharging of wastewater without sufficient treatment results in many environmental issues and negative impact on the local economy. In this study, a novel integrated gravitational-flow wastewater treatment system (IGWTS) for treating domestic wastewater in rural areas was developed and evaluated. As the core module of IGWTS, the multi-soil-layering (MSL) system showed good performances for removing organic matters and nutrients in lab-scale experiments. Aeration was found to be the dominant positive factor for contaminant removal in factorial analysis, while bottom submersion had the most negative effect. Based on the critical operational factors obtained from lab-scale tests, the full-scale IGWTS consisting of multifunctional anaerobic tank (MFAT), MSL, and subsurface flow constructed wetland (SFCW) was designed, constructed, and operated successfully in the field application. The final effluent concentrations of COD, BOD₅, TP, NH₃-N, and TN reached 22.0, 8.0, 0.3, 4.0, and 11.0 mg/L, with removal rates of 92, 93, 92, 86, and 76%, respectively. The feasibility of IGWTS was also quantitatively evaluated from the perspectives of resource consumption, economic costs, water environment impact, and life cycle greenhouse gas (GHG) emissions. IGWTS has been proved to be a sound approach to mitigate GHG emissions compared with centralized wastewater treatment plant. It can also be featured as an eco-friendly technology to improve rural water environment, and an economic scenario with low construction and operation costs. Graphical abstract

The recovery of silver from wastewater is of great significance due to its economic and environmental interest. In this work, zeolitic imidazolate framework-8 (ZIF-8) was chosen to adsorb Ag(I) from wastewater for the first time. The adsorption performance was assessed by adjusting the pH value, uptake time, initial concentration of Ag(I), as well as temperature. The saturated adsorption capacity for Ag(I) onto ZIF-8 can reach 446.7 mg·g⁻¹, which shows that ZIF-8 not only possesses remarkable adsorption performance but also is superior to the reported adsorbents. The selectivity coefficients of ZIF-8 for Ag(I)/Cd(II), Ag(I)/Ni(II), and Ag(I)/Co(II) are 8.242, 8.315, and 136.3, respectively. The Sips adsorption model matches adsorption isotherms of Ag(I) onto ZIF-8 well, and the pseudo-second-order model is more suitable to illustrate the kinetics data. Thermodynamic experiment indicates that the adsorption process of Ag(I) is an exothermic reaction. Mechanism studies suggest that the redox reaction of Ag occur in the adsorption process. In addition, the study of recycling use indicates that the stable adsorption performance being maintained after recycle twice. Thus, a promising adsorbent is introduced to recover Ag(I) from wastewater in this work.

Tobacco stalk, a common agricultural waste derived from the harvest of tobacco, caused serious environmental pollution in China. In this study, the performance of biomethane production and characteristics of four varieties of tobacco stalk were investigated for the first time. The results showed that the highest cumulative methane yield of 130.2 mL/g-VS was obtained from Nicotiana tabacum L., Yunyan114, which had lower lignin content than other varieties of tobacco stalk. Moreover, different kinetic models were used to describe the biomethane production process, and it was found that the modified Gompertz model was more suitable to simulate the anaerobic digestion (AD) of tobacco stalk. The findings of this study not only showed a feasible method for minimizing the pollution issues of tobacco stalk waste but also gave fundamental information for future AD application.

To effectively solve environmental pollution and resource waste problems caused by the rapid growth of express packaging waste, government intervention is needed in the separation and recycling of household waste at the source. Considering the correlation between behavior and individual psychological preference and concerns, this study administered a questionnaire survey (N = 847) and used factor analysis, hierarchical regression, and sensitivity analysis to evaluate the responses and determine the influence of individual focus tendency and empowerment perception on waste recycling behavior. The results showed that individuals with a high prevention focus or a high promotion focus were more likely to have good waste recycling behaviors. Furthermore, the higher the psychological perception of waste recycling empowerment (reflected in the meaning, competence, choice, and impact), the more inclined an individual to participate in recycling and waste reduction activities. In terms of interaction effect, psychological empowerment perception and its dimensions can positively moderate the effect of promotion focus on waste recycling behaviors. In other words, psychological empowerment perception acts as an “amplifier,” and its dimension of meaning was the most important moderating variable. The study results supported policy suggestions to promote individuals’ active participation in waste source separation and recycling activities.

The aim of this study was to determine the photocatalytic performance of copper-doped TiO₂ (Cu-TiO₂) specimens on the degradation of dissolved organic matter (DOM) represented by a model humic acid (HA). TiO₂ was synthesized by sol-gel method from an alkoxide precursor. Cu-doped TiO₂ specimens containing 0.25 wt% and 0.50 wt% Cu were prepared by wet impregnation method using sol-gel synthesized as well as bare TiO₂ P-25 and characterized by XRD, SEM, XPS, Raman spectroscopy, UV-DRS, and BET measurements. Their photocatalytic activities were evaluated with regard to degradation kinetics of HA in terms of UV-vis and fluorescence spectroscopic parameters and organic contents. HA fluorescence excitation emission matrix (EEM) contour plots indicated that the solar photocatalytic degradation pathway was TiO₂-type specific and Cu dopant content.

Selective removal of trace arsenic is crucial for obtaining safe drinking water. Here, the selective adsorptive performance of arsenate (As(V)) on a hybrid ZMAE (nanoscale zirconium molybdate embedded a macroporous anion exchange resin) was examined. It was found that the As(V) adsorption efficiency of ZMAE was almost retained in the presence of competing ions (NO₃⁻ or SO₄²⁻) up an [SO₄²⁻]/[As] or [NO₃⁻]/[As] ratio of 150/1, whereas that of bare AE (anion exchange resin) was negligible for [SO₄]/[As] over 15/1. In addition, the As(V) maximum adsorption capacity of ZMAE was found to be 41.2 mg/g, which is in contrast with the negligible adsorption of bare AE under sulfate-rich condition. The enhanced arsenate selectivity of ZMAE can be attributed to the excellent selectivity of ZM NPs (zirconium molybdate nanoparticles), which contributed up to 45% of the adsorption capacity of ZMAE. The behavior of ZMAE towards arsenate was compared with that towards phosphate showing similar adsorption performances between them, which indicates the similar affinity of ZMAE towards arsenate and phosphate. Finally, ZMAE examined for fixed-bed column adsorption for As(V) removal from synthetic As(V) water was effective for up to 5100 BVs, treating As(V) from 0.1 mg/L to below 0.01 mg/L (meeting the WHO guidelines).

Cadmium (Cd) is a widespread toxic heavy metal trace pollutant worldwide. The ability of Cd absorption and accumulation highly varies among different species and varieties. In order to screen oilseed rape cultivars which are appropriate for cultivation and application in Cd-contaminated soils, we conducted the field trial of 32 oilseed rape varieties in Shifang County of Chengdu Plain. The various biomass, Cd accumulation, and distribution patterns were investigated via determining the Cd concentration in different plant tissues. Moreover, the food safety risks of rapeseeds were finally assessed. The results indicated diverse responses to Cd stress appeared in various tested varieties, including plant biomass, seed yield, Cd concentration, and proportion in different tissues. And most Cd were concentrated in non-edible parts. Through cluster analysis, we found that Nanchongjie, Pengzhoubai, and J-25 belong to high-biomass and high-Cd-accumulated groups in experimental cultivars, which indicated that they could possess more biomass and gather higher Cd content in overground part, so they could be great materials for phytoremediation in Cd-polluted area. Besides, combined with the risk assessment of food safety in rapeseeds, cultivars 72A and 47 with the traits of high yield, low-Cd concentration, and low food safety risk can be considered as suitable materials to widely plant as cash crop. These results provide valuable reference for practical planting and application of oilseed rape in Cd-polluted areas.

Real-time particulate matters (PM₁, PM₂.₅, PM₄, PM₇, PM₁₀, and TSP) with AEROCET 531S (USA), gaseous pollutants (NO₂ and TVOC) with Aeroquel 500 gas sampler (NZ) were measured from the indoor air of houses at four residential locations in Dhaka, Bangladesh. PM₁₀ samples were collected on quartz filters with a dual channel dust sampler (IPM-FDS 2510, India) for selected trace metal determination from five houses of Dhaka. Respiratory function of the occupants was assessed by using a peak expiratory flow meter (Rossmax PF 120). Mean PM₁, PM₂.₅, and PM₁₀ concentrations were 46.1 ± 13.4, 76.0 ± 16.2, and 203.9 ± 44.8 μg m⁻³, respectively. Higher enrichment factors of Pb, Zn, and Ni were found for traffic, industrial, and constructional activities. The correlation between indoor and outdoor PM₂.₅ (R² = 0.42) and ratios (I/O < 1) suggesting indoor air was effected by outdoor air. The concentration of NO₂ (0.076 ± 0.007 ppm) and TVOC (90.0 ± 46.0 ppm) was found above than other studies. The average total hazard ratio (THR) in Dhaka was 9.06 and has the highest exposure to air pollutants (PM₂.₅, PM₁₀, NO₂) in Khilkhet (THR 10.1) residents. A negative association between ultra-fine particles (PM₁) and peak flow rate measurements of the residents living in these houses indicates that inhalations of ultra-fine particles has great influence on the reduced lung efficiency.