Competitive adsorption of Cu2+, Pb2+, Cd2+, and Zn2+ onto water treatment residuals: implications for mobility in stormwater bioretention systems

Preparation of superhydrophilic functionalized nZVI-MOF-74(Co)-PDA@PVDF composite membranes for enhanced Cr(VI) removal

Nano-zero-valent iron (nZVI) is widely employed in heavy metal wastewater treatment; however, it oxidizes and agglomerates readily, forming dense oxide shells that significantly diminish its effectiveness and reduction efficiency. Furthermore, the complete recovery of nZVI from water remains challenging. To address these issues, we successfully integrated nZVI onto the metal-organic framework Co-MOF-74. The framework, rich in pore channels, facilitates the uniform dispersion of nZVI, while open metal sites provide electrons crucial for the reduction of Cr(VI). Subsequently, we synthesized superhydrophilic nZVI-MOF-74(Co)-PDA@PVDF composite membranes (FMPP membranes) by incorporating nZVI-MOF-74(Co) particles into poly(dopamine) (PDA)-modified poly(vinylidene difluoride) (PVDF) powders. These nZVI-MOF-74(Co)-PDA@PVDF composite membranes feature abundant PDA functional groups, such as -OH, -NH, and -NH2, which enhance membrane hydrophilicity and significantly improve oxidation resistance. The equilibrium adsorption capacity for Cr(VI) was 83.12 mg/g at 25°C. The Cr(VI) removal behavior of the FMPP membrane aligns with the pseudo-second-order kinetic model and the Weber-Morris model. The FMPP membrane offers advantages of high efficiency, stability, and reusability. This study demonstrates that FMPP membranes hold great potential for broad application in heavy metal wastewater treatment.

Leaching law of heavy metals in coal gangue: A combination of experimental optimization and simulation

Coal gangue, a solid waste generated during coal mining and washing processes, has caused significant environmental burdens in China. This study aims to optimize and investigate the leaching mechanisms of heavy metals, such as Pb, Zn, and Cu, in coal gangue. The effectiveness of different eluents in removing heavy metals from coal gangue was evaluated by combining experimental methods with software simulations. The leaching conditions (EDTA-2Na concentration of 5 g/L, pH 3, solidliquid ratio of 1:10, leaching time of 4 h, 300 r/min) were optimized to achieve efficient and economical removal of heavy metals. Box-Behnken Design was used to show the key factors of eluant concentration and solid-liquid ratio. The leaching amounts of Pb, Zn, and Cu from coal gangue using EDTA-2Na as a leaching agent were 86 mg/kg, 430 mg/kg, and 66 mg/kg, respectively. The release mechanism and kinetic behavior of heavy metals in the leaching process were studied. The study provided information about leaching mechanisms of heavy metals from coal gangue by experiments and simulations of Visual MINTEQ and DFT that EDTA-2Na enhanced the leaching of heavy metals from coal gangue by enhancing ion exchange and complexation.

Construction of a novel flavonol fluorescent probe for copper (II) ion detection and its application in actual samples

Copper is an essential trace element in the human body, and its level is directly related to many diseases. While the source of copper in human body is mainly intake from food, then the detection of copper ions (Cu2+) in food becomes crucial. Here, we synthesized a novel probe (E)-3-hydroxy-2-styryl-4H-benzo[h]chromen-4-one (NSHF) and explored the binding ability of NSHF for Cu2+ using nuclear magnetic resonance hydrogen spectroscopy (1H NMR), high-resolution mass spectrometry (HRMS), Job's plot method and density functional theory (DFT). NSHF shows the advantages of fast response time, good selectivity and high sensitivity for Cu2+. The fluorescence intensity ratio (F/F0) of NSHF shows a good linear relationship with the concentration of Cu2+ and the detection limit is 0.061 μM. NSHF was successfully applied to the detection of Cu2+ in real samples. In addition, a simple and convenient Cu2+ detection platform was constructed by combining NSHF with a smartphone and a UV lamp, which can realize the rapid detection of Cu2+. This work provides an effective tool for the real-time detection of Cu2+.

Comprehensive Studies of Adsorption Equilibrium and Kinetics for Selected Aromatic Organic Compounds on Activated Carbon

This work presents a comprehensive analysis of the adsorption of selected aromatic organic compounds on activated carbons. Both the equilibrium and kinetics of adsorption were studied using UV-Vis spectrophotometry. The influence of a number of factors: pH, contact time, presence of an accompanying substance, adsorbate concentration, as well as the mass and size of adsorbent grains, on the adsorption process from aqueous solutions was investigated. Phenol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and methylene blue (as an accompanying substance) were selected as adsorbates. GAC 1240W and RIAA activated carbons were used as adsorbents. The equilibrium data were analyzed using the generalized Langmuir isotherm equation (R2 = 0.912-0.996). Adsorption rate data were fitted using a multi-exponential kinetic equation (1 - R2 = (1.0 × 10-6)-(8.2 × 10-4)). As an additional parameter, the half-time was also used to present the influence of selected factors on the adsorption kinetics. An increase in the amount of adsorption was demonstrated with increasing contact time as well as with decreasing solution pH and adsorbent grain size. For selected systems, an increase in the adsorption rate was observed with increasing adsorbate concentration, adsorbent mass and at lower pH values. In some cases, the presence of an accompanying substance also resulted in an increase in adsorption kinetics. In the tested experimental systems, optimal conditions for adsorption were established (T = 298 K, pH = 2, contact time: 7 days, grain diameter: >0.5 mm and the ratio of the mass of the adsorbent to the volume of the adsorbate solution: 1 g/L). Additionally, the acid-base properties (potentiometric titration), morphology (SEM) and structure (TEM) of the used adsorbents were also examined.

Adsorption and desorption behavior of Zn2+ in a flow-through electrosorption reactor

As heavy metal industrial wastewater increases in volume and complexity, we need more efficient, cheaper, and renewable technologies to curb its environmental impact. Compared to advection electrosorption, through-flow electrosorption is a hotspot technique that makes more efficient use of the adsorption capacity of activated carbon fiber mats. A cascade flow-through electrosorption assembly based on activated carbon fiber was used to obtain the best adsorption of Zn2+ in water at a voltage of 2 V, pH value of 8, plate spacing of 3 mm, and temperature of 15°C. The process is more closely fitted to the secondary adsorption kinetic equation and the Langmuir equation. The adsorption capacity of the module decreases at a progressively slower rate with the number of cycles and will eventually retain 75% of its peak value with significant regenerability. The study of this module can provide technical support for treating heavy metal wastewater.

Screening and performance optimization of fungi for heavy metal adsorption in electrolytes

The resource recovery and reuse of precious metal-laden wastewater is widely recognized as crucial for sustainable development. Superalloy electrolytes, produced through the electrolysis of superalloy scrap, contain significant quantities of precious metal ions, thereby possessing substantial potential for recovery value. This study first explores the feasibility of utilizing fungi to treat Superalloy electrolytes. Five fungi resistant to high concentrations of heavy metals in electrolytes (mainly containing Co, Cr, Mo, Re, and Ni) were screened from the soil of a mining area to evaluate their adsorption characteristics. All five fungi were identified by ITS sequencing, and among them, Paecilomyces lilacinus showed the best adsorption performance for the five heavy metals; therefore, we conducted further research on its adsorption characteristics. The best adsorption effect of Co, Cr, Mo, Re, and Ni was 37.09, 64.41, 47.87, 41.59, and 25.38%, respectively, under the conditions of pH 5, time 1 h, dosage 26.67 g/L, temperature 25-30°C, and an initial metal concentration that was diluted fivefold in the electrolyte. The biosorption of Co, Mo, Re, and Ni was better matched by the Langmuir model than by the Freundlich model, while Cr displayed the opposite pattern, showing that the adsorption process of P. lilacinus for the five heavy metals is not a single adsorption mechanism, but may involve a multi-step adsorption process. The kinetics study showed that the quasi-second-order model fitted better than the quasi-first-order model, indicating that chemical adsorption was the main adsorption process of the five heavy metals in P. lilacinus. Fourier transform infrared spectroscopy revealed that the relevant active groups, i.e., hydroxyl (-OH), amino (-NH2), amide (- CONH2), carbonyl (-C = O), carboxyl (-COOH), and phosphate (PO43-), participated in the adsorption process. This study emphasized the potential application of P. lilacinus in the treatment of industrial wastewater with extremely complex background values.

The impact of recycling polyaluminium chloride and anionic polyacrylamide water treatment residuals on heavy metal adsorption in soils: implications for stormwater bioretention systems

Despite the high adsorption capacity of polyaluminum chloride and anionic polyacrylamide water treatment residuals (PAC-APAM WTRs) for Pb2+, Cd2+, Cu2+, and Zn2+, their influence on the adsorption behavior of heavy metals in traditional bioretention soil media remains unclear. This study investigated the impact of PAC-APAM WTRs at a 20% weight ratio on the adsorption removal of Pb2+, Cd2+, Cu2+, and Zn2+ in three types of soils. The results demonstrated improved heavy metal adsorption in the presence of PAC-APAM WTRs, with enhanced removal observed at higher pH levels and temperatures. The addition of PAC-APAM WTRs augmented the maximum adsorption capacity for Pb2+ (from 0.98 to 3.98%), Cd2+ (from 0.52 to 10.99%), Cu2+ (from 3.69 to 36.79%), and Zn2+ (from 2.63 to 13.46%). The Langmuir model better described the data in soils with and without PAC-APAM WTRs. The pseudo-second-order model more accurately described the adsorption process, revealing an irreversible chemical process, although qe demonstrated improvement with the addition of PAC-APAM WTRs. This study affirms the potential of PAC-APAM WTRs as an amendment for mitigating heavy metal pollution in stormwater bioretention systems. Further exploration of the engineering application of PAC-APAM WTRs, particularly in field conditions for the removal of dissolved heavy metals, is recommended.