The efficient removal of heavy metals from aqueous environment is imperative and challenging. A novel ternary composite constructed of diaminopyridine polymers, graphene oxide, and ferrite magnetic nanoparticles was designed by a facile in situ polymerization strategy for the removal of Pb(II) from aqueous solution. Detailed characterization of morphological, chemical, and magnetic properties was employed systematically to confirm the formation of the composite material. Batch adsorption experiment studies suggested that the composite was an excellent adsorbent for Pb(II) which was easily collected after use via exposure to an external magnetic field for 30 s. The effects of different parameters such as solution pH, adsorbent dosage, contact time, initial Pb(II) concentration, temperature, and co-existing ions were examined. The maximum adsorption capacity at pH = 5 was estimated to be 387.2 mg g⁻¹ at 298 K by the Langmuir isotherm model, accompanied by favorable adsorption recyclability according to the investigation of regeneration experiments. Thermodynamic studies revealed that the Pb(II) adsorption via our ternary composite was endothermic and spontaneous. The corresponding removal performance for effluent containing Pb(II) from the battery industry was successfully examined. The present results indicated that our designed adsorbent is beneficial to the practical Pb(II) removal in wastewater purification.

Efficacy of activated bentonite, activated carbon, and natural phosphate under experimental conditions was tested as low-cost adsorbents for spiramycin antibiotic removal from aqueous solution. Equilibrium kinetic and isotherm adsorption process are well described by pseudo-second order and Langmuir isotherm models for activated bentonite and activated carbon, while natural phosphate follows pseudo-first order and Freundlich models, respectively. Obtained results revealed that activated bentonite has the highest adsorption capacity (260.3 mg/g) as compared to activated carbon (80.3 mg/g) and natural phosphate (1.7 mg/g). The adsorption capacity decreases for all adsorbents in the presence of NaCl. The adsorption processes are facilitated in the alkaline pH range for activated bentonite and activated carbon, whereas, for natural phosphate, the acidic pH range is favorable. They are involving ion exchange and hydrogen bond mechanisms as well as Van der Waals forces and also π interactions for activated carbon. Thermodynamic calculation shows that spiramycin adsorption is endothermic and spontaneous on all adsorbents. The activated bentonite reusability is more efficient by more than 95% in two-step desorption using NaOH and HCl eluents compared to activated carbon. Thus, activated bentonite is a promising adsorbent for spiramycin removal from aqueous solution.

Biological reduction is an effective method for removal of perchlorate (ClO₄⁻), where perchlorate is transformed into chloride by perchlorate-reducing bacteria (PRB). An external electron donor is required for autotrophic and heterotrophic reduction of perchlorate. Therefore, plenty of suitable electron donors including organic (e.g., acetate, ethanol, carbohydrate, glycerol, methane) and inorganic (e.g., hydrogen, zero-valent iron, element sulfur, anthrahydroquinone) as well as the cathode have been used in biological reduction of perchlorate. This paper reviews the application of various electron donors in biological perchlorate reduction and their influences on treatment efficiency of perchlorate and biological activity of PRB. We discussed the criteria for selection of appropriate electron donor to provide a flexible strategy of electron donor choice for the bioremediation of perchlorate-contaminated water.

In the present study, the Taguchi design (TD) and the Box-Behnken design (BBD) were used to determine the effect of surfactant concentration, flushing velocity, and dense non-aqueous-phase liquid–trichloroethylene (DNAPL TCE) mass on the time of remediation for the removal of DNAPL zones, which is one of the main persistent sources of groundwater pollution. In the Taguchi approach, the performance of the response variable is measured based on the signal-to-noise (S/N) ratio whereas estimation of the full quadratic model of the parameters is allowed in the Box-Behnken design. The mean experimental values ranged between 3.97–8.31 and 4.01–9.70 for BBD and TD, respectively. Surfactant concentration was identified as the most significant parameter contributing to remediation efficiency in both design techniques. Minimum remediation effort was determined as 5.99 at obtained optimal conditions of surfactant concentration (2.5%), flushing rate (6 cm/h), and DNAPL TCE mass (365 mg) using BBD. In the case of TD, the optimal conditions were determined at a surfactant concentration of 10%, 2 cm/h flushing rate, and 365 mg DNAPL TCE mass. Analysis of variance (ANOVA) revealed a good relationship between the predicted and experimental values with 1.96% and 0.31% of the total variation that was not explained by the model using TD and BBD, respectively. Consequently, from this comparative study, it was concluded that BBD was a more suitable alternative to TD for the evaluation of remediation of DNAPL-contaminated sites.

Lotus seed shell was employed using one-step method combining carbonization with ZnCl₂ activation to synthesize activated carbons because of its inexpensiveness and local accessibility. The lotus seed shell–activated carbons (LSSACs) with the highest surface area (2450.8 m²/g) and mesoporosity (98.6%) and the largest pore volume (1.514 cm³/g) were tailored under optimum conditions as follows: impregnation ratio = 2:1, carbonization temperature = 600 °C, and time = 1.0 h. The surface Zn(II), abundant hydroxyl, and carboxyl functional groups from the activation process could result in rapid Pb(II) adsorption onto the LSSAC surface through surface complexation, ion exchange, or precipitation. The maximum monolayer adsorption capacity (qₘ) for Pb(II) of 247.7 mg/g at 25 °C could be fitted from the Langmuir isotherm. The Gibbs free energy (△G) and positive enthalpy (△H) indicated that the adsorption process was spontaneous and endothermic, and to some extent, it was explained by the intra-particle diffusion mechanism. Our results may provide a promising way to produce activated carbons with high adsorption capacity using solid waste, which will eventually promote the environmental sustainability.

The air pollution problem in Xingtai and Handan is the focus of public attention. The seasonal gray model with fractional order accumulation is proposed to predict the quarterly concentrations of PM₂.₅, PM₁₀, NO₂, and CO in Xingtai and Handan. The new model has higher forecasting performance and can describe the characteristics of seasonal fluctuation very well. The forecasting results indicated that except for the PM₁₀ in Xingtai that will increase slowly, the other indicators in the two places will decrease. The changes of the air quality indicator concentration in different quarters are obvious, and in the same quarter tend to be stable. Except for CO and NO₂ in some seasons, other indicators are in the state of exceeding the standard. The effect of air pollution control is not good. The governance needs to be further strengthened.

In the present study, a multistage route is proposed for the treatment of biodiesel industry wastewater (BWW) containing around 1000 mg L⁻¹ of total organic carbon (TOC), 3500 mg L⁻¹ of chemical oxygen demand (COD), and 1325 mg L⁻¹ of oil and grease. Initially, BWW aerobic biodegradability was assessed via Zhan-Wellens biodegradability test to confirm the appropriate treatment route. Then, a hybrid moving bed bioreactor (MBBR) system was chosen as the first treatment stage. The hybrid MBBR achieved 69 and 68% removal of COD and TOC removals, respectively, and provided great conditions for biomass growth. The bacterial community present in the hybrid MBBR was investigated by PCR-DGGE and potential biodegraders were identified such as: members of Desulfuromonadales, Nocardioidaceae and Pseudomonadaceae. Since biodegradation in the hybrid MBBR alone was unable to meet quality requirements, advanced oxidation processes, such as Fenton and photo-Fenton, were optimized for application as additional treatment stages. Physicochemical properties and acute toxicity of BWW were analyzed after the multistage routes: hybrid MBBR + Fenton, hybrid MBBR + photo-Fenton and hybrid MBBR + UV-C₂₅₄ₙₘ/H₂O₂. Hybrid MBBR + Fenton or photo-Fenton showed overall COD removal efficiencies greater than 95% and removed acute toxicity, thus being appropriate integrated routes for the treatment of real BWW. Graphical abstract ᅟ

Inorganic and organic constituents present in textile effluents have a noticeable effect on the performance of Fenton processes. However, studies have been focused on simple wastewater matrices that do not offer enough information to stakeholders to evaluate their real potential in large-scale facilities. Chemical auxiliaries, commonly present in textile wastewaters (NaCl = 30 g/L, Na₂CO₃ = 5 g/L, and CH₃COONa = 1 g/L), affect both the economic and environmental performance of the process because they increase the treatment time (from 0.5 to 24 h) and the consumption of H₂SO₄ (657%) and NaOH (148%) during conditioning steps. The life cycle assessment (LCA) performed with the IPCC-2013 method revealed that dyeing auxiliaries increase from 1.06 to 3.73 (252%) the emissions of carbon dioxide equivalent (CO₂-Eqv/m³). Electricity consumption can be considered an environmental hotspot because it represents 60% of the carbon footprint of the Fenton process. Also, the presence of auxiliaries is critical for the process because it results in the increase of the relative impact (between 50 and 80%) in all environmental categories considered by the ReCiPe-2008 method. Chemical auxiliaries increased the costs of the treatment process in 178% (US$2.22/m³) due to the higher energy consumption and the additional reagent requirements. It is worthwhile mentioning that the technical simplicity of the Fenton process and its low economic and environmental costs turn this process into an attractive alternative for the treatment of textile effluents in emerging economies.

High contents of azo dyes and heavy metals enter surface waters with the wastewater from dying and dye-manufacturing industries and pose serious threat to fish. In the present study, changes in the ultra-morphological features of the scale have been evaluated as indicators of the stress of lethal and sublethal concentrations of an azo dye Acid Black-1 (AB-1, CI 20470), zinc (Zn), and their mixture AB-1 + Zn to Labeo rohita. Fish were exposed for 96 h to lethal concentration (LC) causing 0–70% mortality, i.e., LC₀, LC₂₀, LC₅₀, and LC₇₀ of AB-1 (4, 6, 8, and 10 mg/L respectively) and Zn (25, 50, 55, and 60 mg/L respectively) and LC₀, LC₅₀, and LC₇₀ of AB-1 + Zn (2 + 15, 2 + 20, and 2 + 25 mg/L respectively). Subchronic exposures of 150 days were given to 1/12, 1/6, and 1/3 of 96 h LC₅₀ values of AB-1, Zn, and AB-1 + Zn. After each exposure, the fish were kept for a recovery period of 90 days. Breakage of circuli, erosion and breakage of lepidonts, uprooting of tubercles, and disappearance of intercircular teeth were observed in all the fish, after 96 h exposure to AB-1, Zn, and AB-1 + Zn. However, damage to focus and holes were common on the scales of Zn-exposed fish. The mixture AB-1 + Zn was more toxic than either of the two as loss of circuli, lepidonts, and intercircular teeth, and sloughing of surface were observed in the scales after 96 h exposure to 2 + 25 mg/L. Damage at this concentration was more than the damage at 8/10 mg/L AB-1 and 55/60 mg/L Zn. After 150 days of exposure, damage due to sublethal concentrations was more than the damage due to all the concentrations of 96 h exposure. Irregular and sloughed circuli were common at 2 + 1.79 and 2 + 3.59 mg/L AB-1 + Zn. Cracks all over the surface (2 + 7.18 mg/L), calcium projections (2 + 3.59 and 2 + 7.18 mg/L), and holes (2 + 7.18 mg/L) hint towards synergistic toxicity of the mixture. It seems that the present dye and metal formed complexes with collagen and osteoblastic cells of the scale that caused an increase in damage during the post-exposure period. Scales of 2 + 7.18 mg/L AB-1 + Zn exposed fish were completely devoid of the normal architectural pattern on the 90th day of the recovery period. Changes in the ultra-morphology of scales at LC₀ (0% mortality) and sublethal concentrations show that these are early indicators of the stress of minute quantities of dyes and metals in water. This is a first report on the cumulative toxicity of the two most abundant components of textile industry effluents.

Hydrothermal synthesis followed by a calcination step was used to prepare porous Zn₂SnO₄ powders using carbon black as a pore-forming agent. The porous Zn₂SnO₄ was used as a photocatalyst to degrade the Rhodamine B dye from aqueous solution under UV artificial light. X-ray diffraction, N₂ adsorption-desorption isotherms, and UV-Vis diffuse reflectance were used to characterize the material. The addition of pore-forming agent (carbon black) did not change the crystalline structure of Zn₂SnO₄ phase. In addition, increasing the surface area and porosity as well as decreasing the band-gap energy was observed. The combination of these characteristics favored the photodegradation of Rhodamine B, reaching 96% of dye degradation at 15 min of reaction time. In addition, the photocatalyst was active after six cycles of reuse. Therefore, the produced material in this work showed to be a potential photocatalyst to remove Rhodamine B dye from aqueous solution.