Removal Of AgNPs Research Articles

Environmental friendly approach on biosorption of Ag nanoparticles using Aspergillus terreus BIOS PTK 6 biomass: Optimization, kinetics and characterization studies

The present study focused on the biosorption of Aspergillus terreus dead biomass for the removal of silver nanoparticles (AgNPs) from aqueous solution. For the better removal of AgNPs, pH, temperature, incubation time, initial biomass concentration and agitation speed were optimized and AgNPs treated as well as control biosorbents were characterized using Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX) analyses. In our study, the optimum conditions of pH, temperature, incubation time, initial biomass concentration and agitation speed for the maximum removal of AgNPs was found to be 4, 30 °C, 200 min, 1 mg/mL and 125 rpm, respectively. Interestingly, in our study, Langmuir isotherm model was best correlated with the highest regression coefficient (R2) of 0.992 and the maximum biosorption was found to be 740.63 μg/mL. FTIR results showed that carboxyl, carbonyl and secondary amine groups were involved in the biosorption of AgNPs. FESEM images of AgNPs treated biosorbent depicted rough surface and the presence of AgNPs on the surface of biosorbent was clearly observed. EDX spectrum showed Ag peak, which confirmed the successful uptake of AgNPs by A. terreus dead biomass. Thus, our study shows that A. terreus could be used as a cost-effective eco-friendly biosorbent for AgNPs removal from aqueous solution. Therefore, exploiting the same fungus for both synthesis and removal of AgNPs could be a novel approach in the context of mycoremediation practices.

Human health risk assessment and uncertainty analysis of silver nanoparticles in water.

Despite frequent detection in environmental waters, literature which quantifies the health risk of silver nanoparticles (Ag NPs) through oral ingestion is scarce. This study compiled literature data to find the removal of Ag NPs from different treatment schemes (i.e., natural, engineered, or hybrid). Ag NP concentrations were found either in surface water or in groundwater based on where the effluent of treatment schemes was discharged, i.e.,either in surface water or in groundwater. Monte-Carlo simulation was carried out for probabilistic assessment of health risks for children for two hypothetical exposure scenarios: (a) ingesting river water while swimming and (b) drinking groundwater. Bio-accessible fraction, dietary metal adsorption factor, and concentrations of silver ions were incorporated to simulate realistic situations. Different treatment schemes were ranked for their nanoparticles' removal efficiency with respect to (i) exceedance probability from guideline value and (ii) health risk to children. Hybrid treatment combinations, i.e., conventional primary and secondary treatment units followed by nature-based units (constructed wetlands and soil aquifer treatment), were ranked the best. The health risk value was found to be less than 1, with the 99th percentile value less than 10-3 in all cases. The maximum allowable concentration of Ag NPs was found to be as low as 1.43 mg/L for groundwater, suggesting probable potential for risk. Uncertainty analysis revealed that the uncertainty of the influent NPs concentration in raw wastewater contributes > 99% to the variance of the hazard index. The results of this work indicate that the use of natural treatment technologies with existing engineered treatments provides higher nanoparticle removal from wastewater without the requirement of any tertiary treatment unit.

Persistence of Silver Nanoparticles Sorbed on Fresh-Cut Lettuce during Flume Washing and Centrifugal Drying

Increased agricultural use of silver nanoparticles (Ag NPs) may potentially lead to residual levels on fresh produce, raising food safety and public health concerns. However, the ability of typical washing practices to remove Ag NPs from fresh produce is poorly understood. This study investigated the removal of Ag NPs from Ag NP-contaminated lettuce during bench-top and pilot-scale washing and drying. Ag NP removal was first assessed by washing lettuce leaves in a 4-L carboy batch system using water containing chlorine (100 mg/L) or peroxyacetic acid (80 mg/L) with and without a 2.5% organic load and water alone as the control. Overall, these treatments removed only 3–7% of the sorbed Ag from the lettuce. Thereafter, Ag NP-contaminated lettuce leaves were flume-washed for 90 s in a pilot-scale processing line using ∼600 L of recirculating water with or without a chlorine-based sanitizer (100 mg/L) and then centrifugally dried. After processing, only 0.3–3% of the sorbed Ag was removed, probably due to the strong binding of Ag with plant organic materials. Centrifugation only removed a minor amount of Ag as compared to flume washing. However, the Ag concentration in the ∼750 mL of centrifugation water was much higher as compared to the flume water, suggesting that the centrifugation water would be preferred when assessing fresh-cut leafy greens for Ag contamination. These findings indicate that Ag NPs may persist on contaminated leafy greens with commercial flume washing systems unable to substantially reduce Ag NP levels.

Enhanced coagulation process for removing dissolved organic matter, microplastics, and silver nanoparticles

Dissolved organic carbon (DOC), microplastics (MPs), and silver nanoparticles (AgNPs) in water are of major concern because of their direct and indirect toxic effects on aquatic organisms and human exposure via water. This work investigated the effect of poly aluminum chloride (PACl) coagulation for reducing DOC, MPs, and AgNPs. This work used water from a canal in Thailand with a DOC of 5.2 mg/L in the experiment. AgNPs of 5–20 mg/L were added to canal water to create synthetic water for the PACl coagulation. Polyethylene and polypropylene (PP) type MPs were identified in the raw water with Fourier transform infrared spectroscopy. Coagulation with 15 mg/L of PACl performed better in the PP removal. The PACl coagulation at dosages of 15, 40, and 70 mg/L removed DOC by 16–20%, 44–52%, and 46–63% and AgNPs by 34–90%, 53–93%, and 81–95%, respectively. The presence of AgNPs at high levels could inhibit the efficiency of DOC reduction by the PACl coagulation. The FESEM identified the adsorption of silver-containing nanoparticles onto the flocs with increased dosages of PACl. So, PACl is a coagulant in the removal of AgNPs that can reduce health hazards and eco-toxicological risks in water sources due to the release of silver.

Fate and removal of silver nanoparticles during sludge conditioning and their impact on soil health after simulated land application

The growing use of silver nanoparticles (AgNPs) in personal care products and clothing has increased their concentrations in wastewater and subsequently in sludge raising concerns about their fate and toxicity during wastewater treatment and after land application of sludge. This research investigated the fate and removal of AgNPs during chemical conditioning of anaerobically digested sludge and their impact on soil bacteria and health after land application. Ferric chloride (FeCl3), alum (Al2 (SO4)3 • (14–18) H2O), and synthetic (polyacrylamide) polymer were used for sludge conditioning. All conditioners effectively removed AgNPs from the liquid phase and concentrated them in sludge solids. Concentration analyses showed that out of 53.0 mg/L of silver in the sludge, only 0.1 to 0.003 mg/L of silver remained in the sludge supernatant after conditioning and 12 to 20% of this value were particulates. Morphological analyses also showed that AgNPs went through physical, chemical, and morphological changes in sludge that were not observed in nanopure water and the resulting floc structures and the incorporation of nanoparticles were different for each conditioner. The impact of conditioned AgNPs on the biological activities of soil was evaluated by investigating its impact on the presence of five important phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria). The results showed that AgNPs at a concentration of 20 mg AgNPs/g soil had a minimal impact on the presence and diversity of the assessed phyla. Also, using different chemicals for sludge conditioning resulted in different growth behavior of studied phyla. This study provides new insight into how the presence of AgNPs and different chemicals used for sludge conditioning might impact the soil biological activities and hence plant growth. The study also provides a solid basis for further research in the risk assessment of nanoparticle toxicity in biosolids amended soils.

Removal of silver nanoparticles using phytoremediation method

This paper presents on removal of silver nanoparticles using phytoremediation. In this study, floating macrophyte (Pistia stratiotes) was used for phytoremediation of silver nanoparticles. This study investigated the performance of Pistia stratiotes in the removal of silver nanoparticles using phytoremediation method. The silver nanoparticles were green synthesized by using Muntingia calabura sp. leaves as reducing and stabilizing agent. The silver nanoparticles were successful synthesized as a peak appeared at wavelength 450 nm by UV-Vis spectrophotometer, while Pistia stratiotes had been acclimatized in tank at laboratory. Similar size of Pistia stratiotes had been employed for investigation. Each selected Pistia stratiotes was placed in 5 L bottles water containing different concentration (0.5 ppm, 1.0 ppm, 2.0 ppm and 3.0 ppm) of silver nanoparticles. This study was evaluated using UV-Vis spectrophotometer for five days. The results showed that the highest removal was achieved 69.88% at concentration of 0.5 ppm. This percentage removal relatively decreased up to 55.61% as concentration increase at 3.0 ppm. These results prescribed that phytoremediation of silver nanoparticles by Pistia stratiotes can be considered to apply and implement in water environment for AgNPs removal.

Purification of Aqueous Media by Biochars: Feedstock Type Effect on Silver Nanoparticles Removal.

Due to the harmful effects of nanoparticles in the environment, their effective removal from aqueous media is of great importance. This paper described the research on the silver nanoparticles (Ag-NPs) sorption on biochars obtained from different feedstock types. The sorbents were produced through pyrolysis (double-barrel method) of the vineyard (BV), paulownia tree (BP), and tobacco (BT). BV exhibited the highest specific surface area, porosity, value of variable surface charge, and content of surface acidic functional groups among the used biochars. The pseudo-second order model best described the obtained adsorption kinetics, whereas the Freundlich model accounted for the registered adsorption data. The Ag-NPs removal was highly efficient in the case of BV, especially in the nanoparticle concentration range 50–500 mg/L. Thus, this biochar can be considered as an ecofriendly, effective, low-cost organic adsorbent, potentially used in the aqueous media purification.

A proposed activated carbon for the removal of silver nanoparticles from water environment

This work aims to propose an activated carbon derived from natural material for the removal of silver nanoparticles (AgNPs) from water environment. The activated carbon was derived from coconut shells via chemical approach. For the description of kinetic mechanism, several kinetic adsorption models were employed. They are the pseudo-first-order, pseudo-second-order, Power, Avrami, mixed 1,2-order, fractal-like pseudo-first-order, and fractal-like pseudo-second-order. This investigation was carried out using a batch experiment. Evaluation of the models was carried out using six statistical indicators. This investigation exhibited that the proposed activated carbon had capability to remove AgNPs from water environment. Kinetic adsorption behavior can be described well using the mixed 1,2-order compared to other employed models. In general, this study successfully proposed activated carbon derived from natural resource for the removal of AgNPs from the environment. This study is useful for the development of natural adsorbent materials for various pollutants removal.

Removal of silver nanoparticles in aqueous solution by activated sludge: Mechanism and characteristics

The increasing production and use of silver nanoparticles (AgNPs) have attracted more and more attention due to their environmental and health risks. Municipal sewage biological treatment unit has been playing an important role in the removal of AgNPs. This study investigated the mechanism and characteristics of AgNPs and their removal from aqueous solution by activated sludge. Results from Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM/EDS) showed that mixed AgNPs were immobilized by activated sludge. It was shown by X-ray photoelectron spectroscopy (XPS) that the fixed AgNPs had an oxidation state of +1. It was inferred by fourier transform infra-red (FTIR) spectra that AgNPs were adsorbed by activated sludge via binding with its primary amino (R-NH2) radical groups on the surface. These results revealed that the major mechanism for the removal of AgNPs by activated sludge was adsorption. The experiment data were in agreement with the Langmuir and Redlich-Peterson isotherms. The maximum adsorption capacity ranged from 12–32 mg g−1 at temperatures of 10–30 °C. Thermodynamic experiment showed that the adsorption of AgNPs by activated sludge was a spontaneous and endothermic reaction. The adsorption kinetics data were in good agreement with the pseudo-second-order model. The factor results indicated that the adsorption of AgNPs onto activated sludge was influenced by electrostatic repulsion, agglomeration, and the process of oxidation and sulfurization.

An Alternative In Vitro Method for Examining Nanoparticle-Induced Cytotoxicity.

Conventional in vitro assays are often used as initial screens to identify potential toxic effects of nanoparticles (NPs). However, many NPs have shown interference with conventional in vitro assays, resulting in either false-positive or -negative outcomes. Here, we report an alternative method for the in vitro assessment of NP-induced cytotoxicity utilizing Fluoro-Jade C (FJ-C). To provide proof of concept and initial validation data, Ag-NPs and Au-NPs were tested in 3 different cell cultures including rat brain microvessel endothelial cells, mouse neural stem cells, and the human SH-SY5Y cell line. Conventional 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and lactate dehydrogenase (LDH) assays were run in parallel with the new method and served as references. The results demonstrate for the first time that FJ-C labeling can be a useful tool for assessing NP-induced cytotoxicity in vitro. Using these approaches, it was also demonstrated that removal of Ag-NPs-while keeping the Ag-ions that were released from the Ag-NPs in culture media-abolished the measured cytotoxicity, indicating that Ag-NPs rather than Ag-ions in solution contributed to the observed cytotoxic effects. Further, co-treatment of Ag-NPs with N-acetyl cysteine (NAC) prevented the observed cytotoxicity, suggesting a protective role of NAC in Ag-NP-induced cytotoxicity. Thus, this alternative in vitro assay is well suited for identify potential cytotoxicity associated with exposure to NPs.

Feasibility study of vertical flow constructed wetland for tertiary treatment of nanosilver wastewater and temporal-spatial distribution of pollutants and microbial community

Silver nanoparticles (AgNPs) have the potential to cause negative effects on nutrient removal in constructed wetlands (CWs), further leading to the deterioration of the water. The current work aimed to investigate the feasibility of vertical flow CW (VFCW) for tertiary treatment of AgNPs wastewater, temporal-spatial distribution of pollutants, and microbial community after 450-day exposure. Results reveal that the effluent of VFCW could still meet the discharge limits except the slightly excessive concentration of phosphorus (>0.5 mg/L) from day 390, with the average removal efficiencies of 83%, 61%, 42%, 70%, and 66% for the chemical oxygen demand, total nitrogen, ammonia nitrogen, total phosphorus, and soluble orthophosphate during 450 days, respectively. Results show that AgNPs removal was relatively stable over time, up to 96%. The temporal-spatial analysis reveals that all contaminants were mainly retained in the soil layer. The Ag concentrations in the upper soil layer and plant roots were higher than that in the lower soil layer and plant stems and leaves, respectively. Microbial sequencing analysis reveals the significant differences in the microbial community at different depths on day 450, with the dominant phyla of Proteobacteria, Acidobacteria, Chloroflexi and Bacteroidetes, and dominant genera of Halomonas and Pseudomonas. These results provide much needed knowledge for the implementation of ecological technologies for AgNPs and nutrient removal simultaneously.

Removal of Silver Nanoparticles from Water Environment: Experimental, Mathematical Formulation, and Cost Analysis

This paper deals with the comprehensive analysis for the removal of silver nanoparticles (AgNPs) from water environment. A new activated carbon derived from an agricultural waste, water lily mango seed shells, was proposed as a low-cost adsorbent to remove AgNPs. In addition, a new simple kinetic model was mathematically formulated and then tested using primary and secondary experimental AgNP adsorption data on different adsorbents. Moreover, cost analysis for the activated carbon production and removal of AgNPs was also estimated. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and inductively coupled plasma mass spectroscopy (ICPMS) analyses were employed for the characterization. The proposed model evaluation was carried out using six statistical indicators, which are the coefficient of determination (R2), root mean squared error (RMSE), percentage of error in maximum estimated value (Emax), percentage of error in minimum estimated value (Emin), mean absolute percent error (MAPE), and mean absolute deviation (MAD). This study found that the proposed activated carbon performed a rapid removal with a maximum percentage of up to 97%. It was also interesting to note that the proposed model outperformed existing kinetic models having the same number of parameters. Cost analysis carried out in this study exhibited that the activated carbon was highly economical compared with other water treatment technologies reported elsewhere.

Rapid and efficient removal of silver nanoparticles from plant surfaces using sodium hypochlorite and ammonium hydroxide solution

With the increasing likelihood of significant release of engineered nanomaterials (ENMs) into the environment, investigations focused on the behavior and impact of ENMs on plant species which have become more important and prevalent. One consistent challenge in these studies is how to separate the plant surface-attached and internalized ENMs. Unfortunately, there are no current effective methods to remove ENMs from plant surfaces. In this study, a protocol was developed to remove surface-attached silver nanoparticles (AgNPs) from spinach leaves. Spinach leaves were exposed to three kinds of AgNPs (2 μg per leaf) for 1 h and 7-day foliar exposure times, including 40 nm CIT- and PVP-AgNPs, and 100 nm CIT-AgNPs. Harvested AgNPs-contaminated spinach leaves were sequentially immersed in solutions of Clorox bleach (sodium hypochlorite, 200 mg/L, 5 min) and ammonium hydroxide (NH3·H2O, 2.8%, 1 min), with a final rinse in deionized (DI) water (1 min). The AgNPs removal efficiency was evaluated by inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM). Both ICP-MS results and SEM images demonstrated effective removal of 91–93% of the surface-attached Ag residuals from the contaminated spinach leaves. This value was significantly higher than removal with DI water (7%), Clorox bleach alone (36%), or NH3·H2O alone (36%). However, no significant changes were observed for the internalized AgNPs, indicating that this method is only surface active. This study provides essential information for the rapid and efficient removal of surface-attached AgNPs and furthers understanding of NP interactions with food crops. Importantly, all chemicals used in this developed washing protocol are generally considered as safe (GRAS), and could readily be used as a postharvest washing procedure to reduce Ag contaminants in leafy vegetables.

Removal of silver nanoparticles coated with different stabilizers from aqueous medium by electrocoagulation

ABSTRACTThis study evaluated the removal of silver nanoparticles (AgNPs), coated with different stabilizers, from aqueous media using the electrocoagulation technique. The AgNPs dispersions were synthesized by chemical reduction with silver nitrate as precursor, sodium borohydride as reducing agent and sodium carboxymethylcellulose (CMC), polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) as stabilizers with initial concentrations of 1 and 3% (w/v). The dispersions were named AgNPs-CMC1, AgNPs-CMC3, AgNPs-PVA1, AgNPs-PVA3, AgNPs-PVP1, and AgNPs-PVP3. Electrocoagulation treatments of AgNPs-PVA1, AgNPs-PVP1 and AgNPs-PVP3 dispersions resulted in total silver removals above 99.90% in 10 min. For the AgNPs-PVP3 dispersion 99.98% of removal was obtained in 20 min. After 15 min of electrolysis, The AgNPs-CMC1 and AgNPs-CMC3 dispersions showed a reduction in total silver concentration of 71.72 and 52.15%, respectively. Therefore, these results showed that the removal of AgNPs from the aqueous medium by electrocoagulation is possible, but their efficiency and viability depends on the nature, the molecular structure and the concentration of stabilizers. Furthermore, the toxicity analysis using the Vibrio fischeri bacteria demonstrated that only the dispersions stabilized with PVP became suitable for disposal after the electrocoagulation treatment.

Removal and fate of silver nanoparticles in lab-scale vertical flow constructed wetland

Engineered nanomaterials (ENMs) are increasingly produced and consequently released into the environment. Therefore, there is a strong need to find a valid way to treat the ENMs pollution. In this study, the removal efficiencies of silver nanoparticles (AgNPs) from synthetic wastewater in lab-scale vertical flow constructed wetland (CW) systems with different operations (plant, hydraulic loading rates, bed depth) were investigated. Moreover, the environmental fate and impacts of AgNPs in CWs were also investigated. The results showed that CWs with plants were more effective in removing AgNPs than the unplanted CWs. Hydraulic loading had a significant effect on the performance of CWs in treating AgNPs, however, the influence of bed depth was negligible. AgNPs stopped in the CWs were mainly resided in the wetland substrate, indicating the main mechanism of AgNPs removal in CWs was through substrate adsorption. Although plant biomass, root activity, peroxidase activity of leaves and biofilm biomass were significantly altered following exposure to AgNPs (P < 0.05), CWs maintained constant high efficiency (63.2–93.8%) in removing AgNPs from wastewater during a continuous 2-month running. Overall, this paper suggests the feasibility and high-efficiency of using CWs to handle AgNPs contamination.

Anti-retroviral therapy- pregnancy induced pharmacokinetic changes–Systematic review and meta- analysis

The use of engineered nanoparticles in the textile industry has been rapidly increasing but their fate during biological wastewater treatment is largely unknown. The goal of the current study was to characterize the interaction of silver nanoparticles (AgNPs), used in the textile industry, with a biological wastewater treatment system based on aerobic granular sludge (AGS). The exposure tests were performed using a laboratory-scale sequencing batch reactor (SBR) system with AGS. The behavior and fate of textile AgNPs in the AGS system was studied with nuclear microscopy techniques. Elemental maps of AGS samples collected from the SBR showed that AgNPs typically clustered in agglomerates of small dimensions (<10 μm), which were preferentially associated with extracellular polymeric substances (EPS). This preliminary study highlights the potential application of nuclear microscopy for the characterization of the behavior and fate of AgNPs in AGS. The detailed compartmentalization of AgNPs in AGS components obtained with nuclear microscopy provides new and relevant information concerning AgNPs retention. This will be important in biotechnological terms to delineate strategies for AgNPs removal from textile wastewater.

A systematic approach of removal mechanisms, control and optimization of silver nanoparticle in wastewater treatment plants

The release of silver nanoparticles (AgNPs) to wastewater caused by over-generation and poor treatment of the remaining nanomaterial has raised the interest of researchers. AgNPs can have a negative impact on watersheds and generate degradation of the effluent quality of wastewater treatment plants (WWTPs). The aim of this research is to design and analyze an integrated model system for the removal of AgNPs with high effluent quality in WWTPs using a systematic approach of removal mechanisms modeling, optimization, and control of the removal of silver nanoparticles. The activated sludge model 1 was modified with the inclusion of AgNPs removal mechanisms, such as adsorption/desorption, dissolution, and inhibition of microbial organisms. Response surface methodology was performed to minimize the AgNPs and total nitrogen concentrations in the effluent by optimizing operating conditions of the system. Then, the optimal operating conditions were utilized for the implementation of control strategies into the system for further analysis of enhancement of AgNPs removal efficiency. Thus, the overall AgNP removal efficiency was found to be slightly higher than 80%, which was an improvement of almost 7% compared to the BSM1 reference value. This study provides a systematic approach to find an optimal solution for enhancing AgNP removal efficiency in WWTPs and thereby to prevent pollution in the environment.

Performance evaluation of Iris pseudacorus constructed wetland for advanced wastewater treatment under long-term exposure to nanosilver

The presence of nanoparticles in the wastewater treatment plants (WWTPs) effluent is a potential threat to the ecosystem due to their effective antimicrobial properties. The aim of this study was to investigate the performance of a pilot-scale vertical flow constructed wetland (VFCW) for advanced wastewater treatment under long-term exposure to silver nanoparticles (AgNPs). The migration and fate of AgNPs were also examined to explore whether the CW had a capability of nanoparticles removal. The results suggested that AgNPs (20 µg/L) showed acutely inhibitory effects on nitrogen and phosphorus removal at the initial exposure stage, followed by the persistent inhibition with time. The average removal efficiencies decreased by 16%, 11%, and 11% for NH+ 4-N, TN, and TP, respectively. For COD removal, no changes were found. The effluent of CW under AgNPs exposure could still reach the first level A of the People's Republic of China's Discharge standard of pollutants for municipal wastewater treatment plant (GB18918-2002). In addition, CW showed a satisfactory AgNPs removal efficiency of 93%. The accumulation of AgNPs in different parts from high to low was soil (88.93%), effluent (7.35%), substrate (3.40%), and plant (0.32%). AgNPs enriched by plant roots were mainly transported to above ground. It demonstrated that the presence of soil layer and wetland plant Iris pseudacorus is essential for AgNPs removal. The study may provide valuable references for evaluating the ecological effects of nanoparticles.

Silver Nanoparticles in the Water Environment in Malaysia: Inspection, characterization, removal, modeling, and future perspective

The current status of silver nanoparticles (AgNPs) in the water environment in Malaysia was examined and reported. For inspection, two rivers and two sewage treatment plants (STPs) were selected. Two activated carbons derived from oil palm (ACfOPS) and coconut (ACfCS) shells were proposed as the adsorbent to remove AgNPs. It was found that the concentrations of AgNPs in the rivers and STPs are in the ranges of 0.13 to 10.16 mg L−1 and 0.13 to 20.02 mg L−1, respectively, with the highest concentration measured in July. ACfOPS and ACfCS removed up to 99.6 and 99.9% of AgNPs, respectively, from the water. The interaction mechanism between AgNPs and the activated carbon surface employed in this work was mainly the electrostatic force interaction via binding Ag+ with O− presented in the activated carbon to form AgO. Fifteen kinetic models were compared statistically to describe the removal of AgNPs. It was found that the experimental adsorption data can be best described using the mixed 1,2-order model. Therefore, this model has the potential to be a candidate for a general model to describe AgNPs adsorption using numerous materials, its validation of which has been confirmed with other material data from previous works.

Investigation of effect of electric field on silver nanoparticles in order to separation of them from aqueous medium using electrocoagulation process

Abstract The behavior of silver nanoparticles (AgNPs) under an applied electric field depends primarily on their stabilizing agent. This research aimed at investigating the behavior of AgNPs and their stabilizers under the electrocoagulation (EC) process. In two separate experiments, sodium citrate and polyvinylpyrrolidone (PVP) were used as the nanoparticles’ stabilizers. Stability of the particles was studied while applying an electrical current with various voltages. Efficiency of the EC process was investigated for these different AgNPs sols. In the case of sodium citrate for various voltages, the plasmon resonance peak of the sample was disappeared after applying the electric field for 90 min, reflecting the removal of AgNPs in the sol by 99.91%. In the case of PVP for various voltages of the EC process for 10 min, the absorbance peak disappeared, and removal efficiency of AgNPs reached 99.98%. Effect of stabilizer concentration on the EC process was investigated. As sodium citrate concentration increased, the stability of AgNPs under an equall applied electric field increased, while the increase of the PVP concentration did not influence on the stability of AgNPs. Kinetic of AgNPs removal was also studied.