Zeolitic imidazole frameworks (ZIFs), a new adsorbent with a high chemical and thermal stability and a high adsorption capacity, are used for adsorptive removal of azo dyes. The synthesized ZIF-67 was characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric–differential thermal analysis (TG–DTA) and zeta potential instrument. The adsorption of some azo dyes on ZIF-67 in the single dye systems showed that the removal efficiencies are congo red > methyl orange > methyl red > methyl blue. The highest adsorption capacity of congo red and methyl orange were 3900 and 1340 mg/g, respectively. In a binary dye system the adsorption capacity of congo red decreased, while the removal efficiency of methyl orange increased in comparison with the single systems, indicating that a competitive adsorption of congo red and methyl orange over the ZIF-67 occurred. The experimental data indicate that the electrostatic attraction between ZIF-67 and congo red is the major driving force and the π–π stacking is also responsible for dye adsorption. After 5 cycles of ZIF-67 adsorption and desorption, the congo red removal efficiency maintained more than 95%. Graphical Abstract The adsorption of Congo red and Methyl orange on the ZIF-67

Acid rain caused a severe loss on agricultural productivity, aggravating the challenge for achieving sustainable food production to feed the increasing globe population. To clarify the mechanism on adaptation of rice root to acid rain, we studied the root morphology and growth regulated by nutrient absorption under hydroponic conditions. Our results show that acid rain (pH 5.0 or 3.5) increased the density of root hair and root volume by increasing concentrations of K⁺, Na⁺, and Ca²⁺ in rice roots, and the root dry weight was increased. However, strong acid rain (pH 2.5) decreased the root length, surface area, volume, and number of root tips by decreasing the concentrations of K⁺, Na⁺, and Mg²⁺ in rice root, and fresh and dry weight were both decreased. After a 5-day recovery, the root morphology of rice seedlings treated with acid rain (pH 5.0 or 3.5) was recovered to the control levels, and the concentrations of K⁺, Na⁺, Ca²⁺, and Mg²⁺ also had no difference from the control (p < 0.05). However, the root growth treated with strong acid rain (pH 2.5) was still lower than the control because the inhibition on root activity and hydrolytic activity of plasma membrane H⁺-ATPase might have exceeded the self-regulating capacity of rice seedlings, and the absorption of mineral nutrient could not sustain the growth. Hence, we concluded that the adaption of root morphology of rice seedlings to acid rain was related to regulation of mineral nutrient absorption in rice root.

Advanced oxidation of bisphenol A (BPA) in aqueous system by O₃/Na₂S₂O₈ was investigated, the degradation of BPA was affected by ozone concentration, persulfate dosages, initial pH, and BPA concentration. Experimental results indicated that the degradation of BPA was proved to follow the pseudo-first order kinetics model and was enhanced with the increase of O₃ concentration and the decrease of initial BPA concentration. pH played a significant role in the BPA removal especially under the alkaline condition. Free radical species in the O₃/Na₂S₂O₈ system were identified by using tertiary butyl alcohol (TBA) and ethanol (ETOH) as two probes, the results found that the major free radical was SO₄ ⁻ · at acidic condition (pH = 3), and the concentration of ·OH increased with the pH increased. Eight products were detected during the reaction according to liquid chromatograph-mass spectrometry analysis. Most of the intermediates contained quinonoid derivatives, carboxylic acid, and the relevant mechanism for BPA degradation by O₃/Na₂S₂O₈ system were proposed.

The morphological, physiological, and biochemical parameters of 6-week-old seedlings of Scots pine (Pinus sylvestris L.) were studied under deficiency (1.2 nM) and chronic exposure to copper (0.32, 1, 2.5, 5, and 10 μM CuSO₄) in hydroculture. The deposit of copper in the seed allowed the seedlings to develop under copper deficiency without visible disruption of growth. The high sensitivity of Scots pine to the toxic effects of copper was shown, which manifested as a significant inhibition of growth and development. The loss of dominance of the main root and a strong inhibition of lateral root development pointed to a lack of adaptive reorganization of the root system architecture under copper excess. A preferential accumulation of copper in the root and a minor translocation in aerial organs confirmed that Scots pine belongs to a group of plants that exclude copper. Selective impairment in the absorption of manganese was discovered, under both deficiency and excess of copper in the nutrient solution, which was independent of the degree of development of the root system. Following 10 μM CuSO₄ exposure, the absorption of manganese and iron from the nutrient solution was completely suppressed, and the development of seedlings was secured by the stock of these micronutrients in the seed. The absence of signs of oxidative stress in the seedling organs was shown under deficiency and excess of copper, as evidenced by the steady content of malondialdehyde and 4-hydroxyalkenals. Against this background, no changes in total superoxide dismutase activity in the organs of seedlings were revealed, and the increased content of low-molecular-weight antioxidants was observed in the roots under 1 μM and in the needles under 5 μM CuSO₄ exposures.

The automobile exhausts are one of the major sources of particulate matter in urban areas and these particles are known to influence the atmospheric chemistry in a variety of ways. Because of this, the oxidation of dissolved sulfur dioxide by oxygen was studied in aqueous suspensions of particulates, obtained by scraping the particles deposited inside a diesel truck exhaust pipe (DEP). A variation in pH showed the rate to increase with increase in pH from 5.22 to about ∼6.3 and to decrease thereafter becoming very slow at pH = 8.2. In acetate-buffered medium, the reaction rate was higher than the rate in unbuffered medium at the same pH. Further, the rate was found to be higher in suspension than in the leachate under otherwise identical conditions. And, the reaction rate in the blank reaction was the slowest. This appears to be due to catalysis by leached metal ions in leachate and due to catalysis by leached metal ions and particulate surface both in suspensions. The kinetics of dissolved SO₂ oxidation in acetate-buffered medium as well as in unbuffered medium at pH = 5.22 were defined by rate law: k ₒbₛ = k ₀ + k cₐₜ [DEP], where k ₒbₛ and k ₀ are observed rate constants in the presence and the absence of DEP and k cₐₜ is the rate constant for DEP-catalyzed pathway. At pH = 8.2, the reaction rate was strongly inhibited by DEP in buffered and unbuffered media. Results suggest that the DEP would have an inhibiting effect in those areas where rainwater pH is 7 or more. These results at high pH are of particular significance to the Indian subcontinent, because of high rainwater pH. Conversely, it indicates the DEP to retard the oxidation of dissolved SO₂ and control rainwater acidification.

Rhodamine B (RhB) is one of synthetic dyes with good stability. Treatment of wastewater containing synthetic dyes has attracted much attention. Heterogeneous activation of peroxymonosulfate (PMS) has been found to be a promising wastewater treatment technology through the activation with metal oxides for the generation of sulfate radicals. In this study, α-MnO₂ was prepared by a simple hydrothermal method and used as the catalyst to activate PMS. The degradation of RhB was studied by the α-MnO₂/PMS system. It was found that the prepared α-MnO₂ exhibited high catalytic activity on the activation of PMS for the degradation of RhB. The degradation of RhB could be well described by the first-order kinetic model. Influences of PMS concentration and α-MnO₂ dose on the degradation of RhB were examined. The chemical oxygen demand (COD) was determined to evaluate the mineralization capability of the α-MnO₂/PMS system. The stability of α-MnO₂ was also investigated through reusability experiments. Quenching tests of radicals were applied to differentiate the contribution of major reactive species for the degradation of RhB by the α-MnO₂/PMS system.

Pentachlorobenzene is one new persistent organic pollutants (POPs) that has been recently added to the Stockholm Convention on Persistent Organic Pollutants. Based on this reason, one treatment having ability to degrade this compound is needed. The microbiological process by using white-rot fungus was used in this experiment. Free cell of Trametes versicolor U80 degraded pentachlorobenzene 43 % in liquid medium at 40 days incubation. The rapid initial uptake of pentachlorobenzene was obtained in the first 20 days. The results based on ionization potential and the partial least square function indicated that both enzymatic systems of lignin peroxidase and P-450 monooxygenase involved in the degradation of pentachlorobenzene. By using addition of Tween 80, MnSO₄, and veratryl alcohol, degradation of pentachlorobenzene could be improved. Based on kinetic study, the use of 1 % of Tween 80 showed the highest degradation rate (2.0619/day) and the degradation of pentachlorobenzene by 50 % can be shortened up to 24 days. Application of T. versicolor U80 in soil and bioreactor degraded pentachlorobenzene 43 and 50 % at 40 days, respectively. T. versicolor U80 shows good capability degrading pentachlorobenzene in soil and bioreactor although it is lower than in liquid due to the difference of pollutant accessibility and transfer oxygen. Finally, strain T. versicolor U80 can be proposed as an excellent candidate for remediation application in pentachlorobenzene pollution.

Adsorption of Reactive Orange 107 dye from aqueous solution was investigated using an activated carbon from Pinus elliottii sawdust chemically prepared with ZnCl₂. The optimum conditions for the adsorption of Reactive Orange 107 dye by the activated carbon, obtained by response surface methodology, were pH = 10, ionic strength = 0.4 mol L⁻¹, agitation rate = 200 rpm, and adsorbent dosage = 0.025 g. For the experimental data of the adsorption equilibrium, nonlinear models, i.e., the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms, were applied; the best correlation was found for the Langmuir model. The thermodynamic parameters were determined using the adsorption equilibrium constant of the Langmuir isotherm and the van ‘t Hoff equation. The parameters suggest an endothermic, ∆H°ₐdₛ = 16.97 kJ mol⁻¹, and spontaneous process, ∆G°ₐdₛ = −23.96, −25.23, −26.78, and −28.05 kJ mol⁻¹, at 298, 308, 318, and 328 K, respectively. The results indicate that the activated carbon was efficient for the adsorption of Reactive Orange 107 and has excellent potential for the treatment of colored effluents.

Insecticides are widely sprayed in modern agriculture for ensuring the crop yield, which could also lead to contamination and insecticide residue in soils. Paichongding (IPP) is a novel neonicotinoid insecticide and was developed recently in China. Soil bacterial community, diversity, and community composition vary widely depending on environmental factors. As for now, little is known about bacterial species thriving, bacterial community diversity, and structure in IPP-spraying soils. In present study, IPP degradation in yellow loam and Huangshi soils was investigated, and bacterial communities and diversity were examined in soil without IPP spray and with IPP spray through pyrosequencing of 16S ribosomal RNA (rRNA) gene amplicons. The degradation ratio of IPP at 60 days after treatment (DAT) reached 51.22 and 34.01 % in yellow loam and Huangshi soil, respectively. A higher richness of operational taxonomic units (OTUs) was found in yellow loam soil (867 OTUs) and Huangshi soil (762 OTUs) without IPP spray while OUTs were relatively low in IPP-spraying soils. The community composition also differed both in phyla and genus level between these two environmental conditions. Proteobacteria, Firmicutes, Planctomycetes, Chloroflexi, Armatimonadetes, and Chlorobi were stimulated to increase after IPP application, while IPP inhibited the phyla of Bacteroidetes, Actinobacteria, and Acidobacteria.

One potential way for organic matter recovering contained in paper mill effluents can be obtaining polyhydroxyalkanoate (PHA). The aim of this work was to evaluate PHA biosynthesis from paper mill effluents by moving bed biofilm reactor (MBBR) under different operational strategies of the BOD₅/nitrogen (N)/phosphorus (P) ratio. The operational strategies were evaluated in two phases. During phase I, organic loading rates (OLRs) were increased from 0.13 to 2.99 biological oxygen demand kg BOD₅ m⁻³ day⁻¹, and in phase II, kg BOD₅ m⁻³ day⁻¹ was increased from 0.81 to 2.83. In both phases, the BOD₅/N/P ratios were 100:5:1 and 100:1:0.3. The maximum percentages of PHA-accumulating cells and organic matter removal were 85.10 and 95.60 % for phase I, both with a BOD₅/N/P ratio of 100:5:1, while in phase II, PHA biosynthesis and organic removal were 89.41 and 97.10 % with 100:1:0.3 and 100:5:1, respectively.