The present research studies the performance of Converter Sludge (CL)as a nano-activator of persulfate (PS) in Permeable Reactive Barrier (PRB) as an in-situ technology for leachate treatment.In batch experiments, the acidic conditions (pH = 3) have been the most suitable for removal operations, where COD and NH3 removal efficiencies are 69.15% and 60.96%, respectively. The Box–Behnken design (BBD) has been employed to optimize three parameters, namely PS/ COD ratio, CS dose, and pore volume (PV), using COD and NH3 of leachate landfill as the target pollutant. The BBD is considered a satisfactory model to optimize the process. Under optimal conditions (PS/COD ratio: 3.47, CS dose: 3.09 g L-1,and PV: 4.27), the measured values of the COD and NH3 removal efficiencies have been 74.2 and 66.8, respectively, all within the 95%-prediction intervals, which indicate the model’s success in predicting removal values. The biodegradability (BOD5/COD) of the real leachate has been enhanced from 0.25 to 0.77, with the toxicity of real leachate getting decreased by more than 90%.

The present research investigates the ability of graphene oxide nanosheets for treatment of dairy wastewater, using In Situ Sludge Magnetic Impregnation” (ISSMI) to separate sludge after adsorption process. To increase the interaction between magnetic nanoparticles and graphene oxide, the former has been functionalized, using 3-Aminopropyl triethoxysilane, with the synthesized graphene oxide and magnetic nanoparticles being characterized by FT-IR, SEM, and NCHS analysis. The experiments have been conducted on the effluent of Pegah factory. The batch adsorption experiments have been carried out to investigate the effect of adsorbent dose, contact time, and pH on the removal of total nitrogen, total phosphorus, COD, and turbidity. At adsorbent dose of 320 mg L-1, the removal efficiencies of 90, 80, 84, and 94% have been observed for TN, TP, COD, and turbidity, respectively. The adsorbent data has been modeled by Langmuir and Freundlich isotherms, giving results that are compatible with Freundlich isotherm. TN, TP, and COD are mostly particulate materials in dairy wastewaters; therefore, when nanosheets aggregate, particulate materials are trapped between GO nanosheets; as a result, pollutants are distributed heterogeneously on the adsorbent's surface. Consequently, adsorption does not occur as monolayer on the surface of GO; for this reason, adsorption follows Freundlich model. Maximum absorption capacity of the adsorbent turns out to be 730 mg g-1 for total nitrogen, 600 mg g-1 for total phosphorus, 26000 mg g-1 for COD, and 5500 mg g-1 for turbidity. Adsorption kinetic has been studied with the first and second order equation, giving results that are compatible with second order equation.

Duckweeds are of special interest, as they are naturally growing weeds that have the capacity to tolerate and remove toxic pollutants, including heavy metals from the environment. Studies have revealed that duckweed (Lemna minor) can tolerate and remove heavy metals from aqueous solutions. In the present study, the efficiency of L. minor in the removal of Ni and Cr individually from aqueous solutions was investigated at concentrations of 3.05, 3.98 and 4.9 mg/L for Ni and 1.91, 2.98, and 4.2 mg/L for Cr. Experiments were run for 22 days, after which the metal content in the plant was estimated by atomic absorption spectrophotometer (AAS). The duckweed showed higher percentage of Ni removal than Cr. Specific Growth Rate (SGR) was found to be reduced at high concentrations of both Ni and Cr. Statistical analysis suggested that the growth of the plant was affected by the toxic effect of both Ni and Cr. Bioaccumulation of Ni was higher than Cr in L. minor. The mechanism of removal of both Ni and Cr followed second order kinetics. It is suggested that these duckweeds can remove Ni and Cr from aqueous solution and can also accumulate the same in considerable concentrations, at low initial metal concentrations.

Hydrogen sulfide (H₂S) is a flammable, corrosive and lethal gas even at low concentrations (ppm levels). Hence, the capture and removal of H₂S from various emitting sources (such as oil and gas processing facilities, natural emissions, sewage treatment plants, landfills and other industrial plants) is necessary to prevent and mitigate its adverse effects on human (causing respiratory failure and asphyxiation), environment (creating highly flammable and explosive environment), and facilities (resulting in corrosion of industrial equipment and pipelines). In this review, the state-of-the-art technologies for H₂S capture and removal are reviewed and discussed. In particular, the recent technologies for H₂S removal such as membrane, adsorption, absorption and membrane contactor are extensively reviewed. To date, adsorption using metal oxide-based sorbents is by far the most established technology in commercial scale for the fine removal of H₂S, while solvent absorption is also industrially matured for bulk removal of CO₂ and H₂S simultaneously. In addition, the strengths, limitations, technological gaps and way forward for each technology are also outlined. Furthermore, the comparison of established carbon capture technologies in simultaneous and selective removal of H₂S–CO₂ is also comprehensively discussed and presented. It was found that the existing carbon capture technologies are not adequate for the selective removal of H₂S from CO₂ due to their similar characteristics, and thus extensive research is still needed in this area.

The current study is the first attempt to prepare nanocomposites of Eleocharis dulcis biochar (EDB) with nano zero-valent Copper (nZVCu/EDB) and magnetite nanoparticles (MNPs/EDB) for batch and column scale sequestration of Congo Red dye (CR) from synthetic and natural water. The adsorbents were characterized with advanced analytical techniques. The impact of EDB, MNPs/EDB and nZVCu/EDB dosage (1–4 g/L), pH (4–10), initial concentration of CR (20–500 mg/L), interaction time (180 min) and material type to remove CR from water was examined at ambient temperature. The CR removal followed sequence of nZVCu/EDB > MNPs/EDB > EDB (84.9–98% > 77–95% > 69.5–93%) at dosage 2 g/L when CR concentration was increased from 20 to 500 mg/L. The MNPs/EDB and nZVCu/EDB showed 10.9% and 20.1% higher CR removal than EDB. The adsorption capacity of nZVCu/EDB, MNPs/EDB and EDB was 212, 193 and 174 mg/g, respectively. Freundlich model proved more suitable for sorption experiments while pseudo 2nd order kinetic model well explained the adsorption kinetics. Fixed bed column scale results revealed excellent retention of CR (99%) even at 500 mg/L till 2 h when packed column was filled with 3.0 g nZVCu/EDB, MNPs/EDB and EDB. These results revealed that nanocomposites with biochar can be applied efficiently for the decontamination of CR contaminated water.

Hg pollution is a global concern due to its high ecotoxicity and health risk to human beings. A comprehensive understanding of the fast-developed technology applied in determining and controlling Hg pollution is beneficial for risk assessment and field remediation. Herein, we mainly assembled the recent progress on Hg treatment in the environment by nanotechnology. The advantages and disadvantages of the conventional and nanotechnology-based methods commonly used in water-/soil-Hg remediation were compared and summarized. Specifically, green nanomaterials derived from plant tissues (e.g., nanocellulose) have prominent merits in remediation of Hg contaminated environments, including high efficiency in Hg removal, low cost, environment-friendly, and easily degradable. Based on the theories of Hg biogeochemistry and existed researches, four promising pathways are proposed, 1) developing surface-modified green nanocellulose with high selectivity and affinity towards Hg; 2) designing effective dispersants in preventing nanocellulose from agglomeration in soil; 3) mediating soil properties by adding green nanomaterials-based fertilizers; 4) improving plant-Hg-extract capacity with green nanomaterials addition. Briefly, more efficient and available approaches are still expected to be developed and implemented in the natural environment for Hg remediation.

The increased occurrence of Mercury (Hg II) contaminant has caused environmental and health concerns worldwide. Removal of Hg(II) from water is of significant interest, in particular if these can be coupled in a manner of detection. Here, a novel activated carbon (AC) adsorbent and a fast detection device to form a closed-cycle strategy was developed. The synthesis of conjugates of streptavidin-biotinylated DNA probes modified gold nanoparticle was used with lateral flow biosensors for Hg(II) detection. A quantification was completed via a self-developed smartphone app and its limit of detection was 2.53 nM. Moreover, AC was activated with a new activating agent of diammonium hydrogen phosphate. The adsorbent was characterized and determined to have an amorphous microporous structure with a high surface area (1076.5 m² g⁻¹) and demonstrated excellent removal efficiency (99.99%) and adsorption capacity (∼100 mg g⁻¹) for Hg(II). The kinetics of the pseudo-second-order model and the mechanisms of electrostatic adsorption, ion exchange, and complex reactions are provided. The proposed closed-cycle strategy can be useful for early, fast, and mobile detection of Hg (II) pollution, followed by its effective removal during water treatment.

Microplastics (MPs) contamination in water environment has recently been documented as an emerging environmental threat due to their negative impact on the ecosystem. Their sources are many, but all of them are from synthetic materials. The sources of MPs are cosmetics and personal care products, breakdown or abrasion processes of other plastic products, textile and tyre, bitumen and road marking paints. Because of their low density and small particle size, they are easily discharged into the wastewater drainage systems. Therefore, the municipal wastewater treatment plants (WWTPs) are indicated to be the main recipients of MPs before getting discharged into the natural waterbodies. Therefore, understanding the occurrence and fate of MPs in WWTPs are of great importance towards its control. The aim of this article is to provide a comprehensive review to better understand the pathways of MPs before entering the WWTPs, characteristics of MPs in wastewater, and the removal efficiency of MPs of the existing wastewater treatment technologies adopted by the WWTPs. This review also covers the development of potential microplastics treatment technologies investigated to date. Based on the review of existing literature, it is found that the existing WWTPs are inefficient to completely remove the MPs and there is a risk that they may get discharged into the ambient water sources.

Groundwater with elevated As concentrations is a global concern, and low-cost, high-efficiency removal technologies are necessary. Therefore, we have prepared three adsorbent FeMnLa-impregnated biochar composites (FMLBCs) for the efficient removal of As(III) from aqueous solutions and characterized them using a variety of techniques. We found that the efficiency of As(III) removal increased with increasing La content and that the removal mainly occurred via adsorption and oxidation. Moreover, the removal of As(III) by FMLBCs was rapid and was best fitted to a pseudo-second-order kinetic model. The adsorption isotherms were well described by the Langmuir equation, and the maximum As(III) adsorption capacity was 15.34 mg g⁻¹. These results highlight the significant potential of FMLBCs as adsorbents for As(III) removal from aqueous solutions.

The removal of antibiotics in subsurface flow constructed wetlands is performed through various removal mechanisms, such as adsorption, hydrolysis, microbial degradation and plant uptake. However, the contribution rates of the removal mechanisms in constructed wetlands are still not well studied. This study conducted a series of experiments and used multivariate statistical analysis to determine contribution rates for substrate adsorption, hydrolysis, and microbial degradation. Multiple stepwise regression analysis indicated that specific surface area and salt content were the main factors influencing sulfonamide adsorption, while temperature and pH were the main factors influencing sulfonamide hydrolysis. Variance partitioning analysis showed that the influence of physical-chemical factors was greater than that of nutrients on the microbial community. Partial least squares path analysis showed that the path coefficients of microbial degradation, adsorption and hydrolysis for sulfonamides removal in vertical subsurface flow constructed wetlands were 0.6339, 0.3608 and 0.0351, respectively, while the corresponding path coefficient were 0.5658, 0.4707 and 0.1079 in horizontal subsurface flow constructed wetlands, respectively. This means that microbial degradation contributes the most to the removal of sulfonamides in subsurface flow constructed wetlands. Enhanced microbial degradation may be a powerful measure to improve the removal of sulfonamides. These results will be helpful for understanding the removal mechanism of antibiotics and will provide a definite direction for pertinently improving sulfonamide removal efficiency in constructed wetlands.