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.

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.

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.

Studies on the presence and fate of household and personal care chemicals (HPCCs) in wastewater treatment plants (WWTPs) are important due to their increasing consumption worldwide. The seasonal patterns and removal mechanisms of HPCCs are not well understood for WWTPs that apply different treatment technologies. To answer these questions, the sewage and sludge samples were taken from 10 typical WWTPs in Northeast China. Levels of UV filters in the influents in the warm season were significantly greater than that of the cold season (p < 0.05). Significant seasonal differences were found for the removals of many HPCCs. Results revealed that the highest removal efficiencies were found for linear alkylbenzene sulphonates with values ranging from 97.2% to 99.7%, and the values were 50.0%–99.9% for other HPCCs. The SimpleTreat model demonstrated that the studied WWTPs were operating with high efficiency at the time of sampling. The sorption of HPCCs to sludge can be strongly associated with their physicochemical parameters. Mass balance calculation suggested that sorption was the dominant mechanism for the removal of antimicrobials, while degradation and/or biotransformation were the other mechanisms for removing the most HPCCs in the WWTPs. This study real the factors influencing the seasonal patterns and removal mechanisms which imply the need for further studies to fully understands the plant and human health implications as sludge could be used in the municipal land application of biosolids.

Wastewater treatment plants (WWTPs) are considered one of the important sources of aquatic/terrestrial microplastic (MP) pollution. Therefore, the abundance and properties of MPs in the wastewater and sludge of an urban WWTP in Bursa Turkey were investigated. The amount, properties, and removal of MPs were evaluated. The results showed that the average abundance of MPs was 135.3 ± 28.0 n/L in the influent and 8.5 ± 4.7 n/L in the effluent, with a 93.7% removal rate, MP was removed and transferred to the sludge. The daily MP amount released in the aquatic environment is calculated as 525 million MPs, and the annual amount is 1.9 × 10¹¹ MPs. The abundance of MPs in the sludge thickening and sludge filter cake is 17.9 ± 2.3 and 9.5 ± 2.3 n/g dry weight (dw), respectively. The sludge disposal amount of WWTP is 81.5 tons/day and the approximate amount of MP accumulated in the sludge per year is calculated as 2.8 × 10¹¹ MPs. In wastewater and sludge samples, fragment dominant shape, black main colour, and 500–1000 μm sizes are the most common size. The main MP types in wastewater samples at the influent are polypropylene (PP, 36.8%), polyethylene (PE, 31.0%), polystyrene (PS, 11.8%), polyethylene terephthalate (PET, 8.0%), and polyamide (PA, 7.1%), at the effluent (PE, 33.0%), (PP, 52.5%), and (PS, 8.2%). In the sludge cake, the distribution is (PE, 40.8%), (PP, 27.6%), (PS, 18.7%) and (PET, 8.0%). The results of this study show that MPs are removed from wastewater with high efficiency by treatment processes and a significant amount accumulates in the sludge. Therefore, it is suggested that to integrate advanced treatment processes into urban WWTPs and use effective sludge disposal management practices to reduce the amount of MP released into the environment with effluent and sludge.

In recent years, antibiotic pollution has become worse, especially in China. In this study, the ecotoxicological effects of four frequently used antibiotics with different lipophilic degrees (log Kow) (sulfadiazine (SD), sulfamethazine (SM2), enrofloxacin (ENR), and norfloxacin (NOR)) at four concentrations of 1, 5, 20, and 50 mg L⁻¹ were examined using batch cultures of green alga Chlorella vulgaris and cyanobacterium Chrysosporum ovalisporum for 16 days based on changes in chlorophyll fluorescence parameters (chl a, Fv/Fm, and ΦPSII) and responses of the antioxidant system. Besides, the antibiotics removal efficiencies of the two microalgae were investigated. Sulfonamides (SD and SM2) had no significant inhibitory effect on the growth of C. ovalisporum, but had an inhibitory effect on C. vulgaris, whereas fluoroquinolones (ENR and NOR) significantly inhibited C. ovalisporum. The activities of superoxide dismutase, catalase, and glutathione reductase suggested that C. vulgaris was more tolerant to these antibiotics than C. ovalisporum. The increased malondialdehyde level in both algae indicated their tolerance against antibiotics. When compared with C. ovalisporum, C. vulgaris presented better capacity to remove antibiotics. In summary, the four antibiotics exerted time- or concentration-dependent ecotoxicological effects on the microalgae examined, whereas the microalgae could remove the antibiotics based on the log Kow of the antibiotics. The findings of this study contribute to effective understanding of the ecotoxicological effects of antibiotics and their removal by microalgae.

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.

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.

Brominated flame retardants (BFRs) are widely used because of their excellent flame retardant performance and are frequently detected in the soil environment. Their adverse impacts on soil organisms cannot be ignored. The enrichment and removal dynamics of the five BFRs (pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ethane (DBDPE), and decabromodiphenyl ether (BDE209)) in earthworms and different tissues (epidermis, intestinal tract, and cast) in the presence of co-exposure were explored for the first time. The results showed that the enrichment of the five BFRs in earthworms increased with increasing exposure concentration and time. The distribution of these chemicals in different tissues of earthworms was different. The contents of HBB and PBT in the intestine and epidermis were the highest and were more than 60% during most of the time. Additionally, the contents of BTBPE, BDE209, and DBDPE were significantly increased while the contents of HBB and PBT were significantly decreased in the cast. The correlation analysis indicated that HBB and PBT had a significant relationship in all the tissues, but BDE209 and DBDPE only had a relationship in the cast, which might be attributed to the structure of the pollutants. Additionally, the experiments illustrated that earthworms had strong removal for HBB and PBT, but were weak for DBDPE and BDE209.