Increasing the pollution rate of water sources is one of the most severe issues that the world faces. This issue has stimulated researchers to investigate different treatment methods such as adsorption, chemical precipitation, membrane filtration, flocculation, ion exchange, flotation, and electrochemical methods. Among them, adsorption has gained broad interest due to its ease of operation, low cost, and high efficiency. The critical factor of the successful adsorption treatment process is finding attractive adsorbents with attractive criteria such as low cost and high adsorption capacity. In the last few decades, nanotechnology has attracted much attention, and numerous nanomaterials have been synthesized for water and wastewater treatment. This work provides a quick overview of nanomaterials, which have been investigated for water remediation as adsorbent and photocatalyst. This work reviewed more than 100 articles to provide a critical review that would determine the limitation of using nanomaterials in water treatment at the commercial scale.

The present study prepares alkali lignin (AL) via acidification of black liquor, obtained from a pulp and paper factory. The average molecular weight of AL (equal to 2,530 g/mol) has been determined with gel permeation chromatography. AL has been modified by ethylene glycol, while lignin nanoparticles (LN) has been prepared through acid precipitation technology, their size being assessed by means of DLS to show that the average diameter of the nanoparticles at pH = 4 has been 52.7 nm. Afterwards, it has used AL and LN to remove Basic Red 2 (BR2) from aqueous solutions. The absorbent structures and morphologies of AL and LN have been investigated using SEM, and FT-IR spectroscopy. The optimal conditions for the absorption of AL and LN, using 0.1 gr of the absorbent, include 100 min of duration, at pH of 7, and an initial dye concentration amounting to 100 mg/L. Furthermore, the absorption amount has been mathematically described as a function of experimental parameters, modeled by means of Response Surface Methodology (RSM). A central composite design (CCD) has been applied to evaluate the impacts of four independent variables. Optimum absorption values, obtained via empirical methods, completely match with the values, calculated by the program called Design-Expert. Both absorbent AL and LN show agree with Langmuir Isotherm with maximum absorption capacities of AL and LN being 55.2 mg/gr and 81.9 mg/gr, respectively. The experimental results show that both absorbent LN and AL follow both pseudo-second kinetic and the intraparticle diffusion models.

The study investigates the effect of aluminium oxide nanoparticles as an additive to Madhuca Indica (mahua) methyl ester blends on performance, emission analysis of a single-cylinder direct injection diesel engine operated at a constant speed at different operating conditions. The test fuels are indicated as B10A0.2, B10A0.4, B20A0.2, B20A0.4 and diesel respectively. The results indicate that the brake thermal efficiency for aluminium oxide nanoparticles blended biodiesel increases slightly when compared to the mineral diesel. The carbon monoxide (CO), unburnt hydrocarbon (HC) and smoke emission marginally decrease as compared to mineral diesel. Oxides of nitrogen (NOx) emissions are minimum for the aluminium oxide nanoparticles blended mahua methyl esters. Higher cylinder gas pressure and heat release rate were observed for aluminium oxide nanoparticles blended mahua methyl ester. From the study, the blending of aluminium oxide nanoparticles in biodiesel blends produces a most promising results in engine performance and also reduces the harmful emission from the engines.

Conventional remediation techniques have become outdated and insufficient to treat the influx of pollution from different fronts (air, water, and soil). Green synthesis of nanoparticles is an eco-friendly approach to remediate these contaminants and Membrane technology is increasingly becoming popular for the treatment of wastewater due to their efficiency and versatility against a wide array of contaminants. Cellulose acetate (CA) is a polymer obtained from cellulose and hence considered biodegradable, making it a more environmentally friendly option over other conventional polymers. In this present study, silver nanoparticles were synthesized using Staphylococcus aureus and characterized by UV-vis Spectrometer, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX). The synthesized green silver nanoparticles were assimilated onto synthesized CA membrane films to fabricate nanocomposite membranes (CA-X, CA-X1 and CA-X2). EDAX results showed higher counts of silver at 3keV on the CA-X, confirming that silver nanoparticles were properly embedded on the membrane. Physio-chemical tests performed on the collected sewage, showed that the total dissolved solids (TDS) were found to decrease significantly during the first hour of treatment, CA-X1 showed 16.2% decrease and 21.95% decrease was observed by CA-X2. A decrease in total nitrogen content by 38.88% and 41.36% for CA-X1 and CA-X2 respectively was recorded after a week’s treatment. Therefore, the work displayed the capability of cellulose acetate nanocomposite membrane for leachate treatment, since it displayed its potential in remediating leachate in a short span of time and scalability could be achieved for a larger volume of leachate with larger nanocomposite membranes.

This work explores the synthesis and characterization of two novel nanocomposites that can be used in various applications, such as aqueous solution adsorption of pollutants. The first nanocomposite consists of tin (Sn)-doped titanium dioxide (TiO2) on activated carbon, while the other one consists of polypyrole (PPy), chitosan (CS), and Sn-doped TiO2. A contrast was made of their effective adsorbent materials for the removal of Cibacron Brilliant Yellow dye from aqueous solutions. Different analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDX), and Fourier transform - infrared (FT-IR) were used to analysis the nanocomposite samples. SEM images show that the average particle diameter of PPy-CS/Sn-doped TiO2 NC is 75 ± 3 nm, while Sn-doped TiO2/AC particles have an average diameter of 40 ± 2 nm. The greater PPy-CS/Sn-doped TiO2 nanocoposite particle diameter indicates that the polymers cover the Sn-doped TiO2 nanoparticles, which leads to higher in the diameter of the particles. The adsorption efficiency of Sn-doped TiO2/AC was higher than that of PPy-CS/Sn-doped TiO2 sample due to its smaller particle size which resulted in a higher surface area which provides more adsorption sites. However, both samples showed remarkable adsorption capacity, where the adsorption capacity of Sn-doped TiO2/AC and PPy-CS/Sn-doped TiO2 were 104 and 103 mg/g, respectively.

peer reviewed | Copper and zinc are metals that have been traditionally thought of as past contamination legacies. However, their industrial use is still extensive and current applications (e.g. nanoparticles and antifouling paints) have become additional marine environment delivery routes. Determining a pollutant's genotoxicity is an ecotoxicological priority, but in marine benthic systems putative substances responsible for sediment genotoxicity have rarely been identified. Studies that use sediment as the delivery matrix combined with exposures over life-history relevant timescales are also missing for metals. Here we assess copper and zinc's genotoxicity by exposing the ecologically important polychaete Alitta virens to sediment spiked with environmentally relevant concentrations for 9 months. Target bioavailable sediment and subsequent porewater concentrations reflect the global contamination range for coasts, whilst tissue concentrations, although elevated, were comparable with other polychaetes. Survival generally reduced as concentrations increased, but monthly analyses show that growth was not significantly different between treatments. The differential treatment mortality may have enabled the surviving worms in the high concentration treatments to capture more food thus removing any concentration treatment effects for biomass. Using the alkaline comet assay we confirm that both metals via the sediment are genotoxic at concentrations routinely found in coastal regions and this is supported by elevated DNA damage in worms from field sites. However, combined with the growth data it also highlights the tolerance of A. virens to DNA damage. Finally, using long term (decadal) monitoring data we show stable or increasing sediment concentrations of these metals for many areas. This will potentially mean coastal sediment is a significant mutagenic hazard to the benthic community for decades to come. An urgent reappraisal of the current input sources for these ‘old pollutants’ is, therefore, required. Chronic exposure of zinc and copper via sediment at environmentally relevant concentrations induces DNA damage in a marine polychaete. © 2018 Elsevier Ltd

International audience | The ability of metallic nanoparticles to be oxidized, reduced or dissolved in biological media can be used to predict their toxicity in vitro. a b s t r a c t The level of production of nanoparticles will inevitably lead to their appearance in air, water, soils, and organisms. A theoretical framework that relates properties of nanoparticles to their biological effects is needed to identify possible risks to human health and the environment. This paper considers the properties of dispersed metallic nanoparticles and highlights the relationship between the chemical stability of these nanoparticles and their in vitro toxicity. Analysis of published data suggests that chemically stable metallic nanoparticles have no significant cellular toxicity, whereas nanoparticles able to be oxidized, reduced or dissolved are cytotoxic and even genotoxic for cellular organisms.

Metal-based nanoparticles (NPs) are considered detrimental to aquatic organisms due to their potential accumulation. However, little is known about the mechanisms underlying these effects and their species-specificity. Here we used stable silver (Ag) NPs (20 nm, from 10 to 500 μg/L) with a low dissolution rate (≤2.4%) to study the bioaccumulation and biological impacts in two freshwater gastropods: Lymnaea stagnalis and Planorbarius corneus. No mortality was detected during the experiments. Ag bioaccumulation showed a dose-related increase with an enhanced concentration in both species after 7d exposure. L. stagnalis displayed a higher accumulation for AgNPs than P. corneus (e.g., up to 18- and 15-fold in hepatopancreas and hemolymph, respectively) which could be due to the more active L. stagnalis having greater contact with suspended AgNPs. Furthermore, the hepatopancreas and stomach were preferred organs for bioaccumulation compared to the kidney, mantle and foot. Regarding biological responses, the hemolymph rather than hepatopancreas appeared more susceptible to oxidative stress elicited by AgNPs, as shown by significantly increasing lipid peroxidation (i.e., formation of malondialdehyde). Neurotoxicity was detected in L. stagnalis when exposed to high concentrations (500 μg/L). Comparison with impacts elicited by dissolved Ag revealed that the effects observed on AgNPs exposure were mainly attributable to NPs. These results highlighted the relationship between the physiological traits, bioaccumulation, and toxicity responses of these two species to AgNPs and demonstrated the necessity of species-specificity considerations when assessing the toxicity of NPs.

Arsenic (As) contamination and bioaccumulation are a serious threat to agricultural plants. To address this issue, we checked the efficacy of As tolerant plant growth promoting bacteria (PGPB), zinc oxide nanoparticles (ZnO NPs) and oxalic acid (OA) in Luffa acutangula grown on As rich soil. The selected most As tolerant PGPB i.e Providencia vermicola exhibited plant growth promoting features i.e solubilzation of phosphate, potassium and siderophores production. Innovatively, we observed the synergistic effects of P. vermicola, ZnO NPs (10 ppm) and OA (100 ppm) in L. acutangula grown on As enriched soil (150 ppm). Our treatments both as alone and in combination alleviated As toxicity exhibited by better plant growth and metabolism. Results revealed significantly enhanced photosynthetic pigments, proline, relative water content, total sugars, proteins and indole acetic acid along with As amelioration in L. acutangula. Furthermore, upregulated plant resistance was manifested with marked reduction in the lipid peroxidation and electrolyte leakage and pronounced antagonism of As and zinc content in leaves under toxic conditions. These treatments also improved level of nutrients, abscisic acid and antioxidants to mitigate As toxicity. This marked improvement in plants’ defense mechanism of treated plants under As stress is confirmed by less damaged leaves cell structures observed through the scanning electron micrographs. We also found substantial decrease in the As bioaccumulation in the L. acutangula shoots and roots by 40 and 58% respectively under the co-application of P. vermicola, ZnO NPs and OA in comparison with control. Moreover, the better activity of soil phosphatase and invertase was assessed under the effect of our application. These results cast a new light on the application of P. vermicola, ZnO NPs and OA in both separate and combined form as a feasible and ecofriendly tool to alleviate As stress in L. acutangula.

Titanium dioxide nanoparticles (TiO₂ NPs) easily combine with other pollutants such as heavy metals because of their excellent physiochemical properties. However, how such an interaction may affect the binding behavior of metals onto biofilms remains largely unclear. This study, examined the effects of TiO₂ NPs on Cd²⁺ accumulation and toxicity for natural periphytic biofilms were examined. The adsorption kinetics showed that adding 0.1 and 1 mg/L TiO₂–NPs increased the Cd²⁺ adsorption of biofilms at equilibrium by 23.5% and 35.8%, respectively. However, adding 10 mg/L TiO₂ NPs increased the Cd²⁺ adsorption of biofilms at equilibrium by only 1.9%. The adsorption isotherms indicate that the presence of TiO₂ NPs considerably increased the Cd²⁺ adsorption capacity of the biofilms; however, this effect became less prominent at high TiO₂ NP concentrations. The optimum pH for Cd²⁺ adsorption increased with increasing Cd²⁺ and TiO₂ NP contents. At low concentrations, the coexistence of Cd²⁺ and TiO₂ NPs may facilitate their respective accumulation by stimulating the secretion of extracellular polymeric substances and enhancing the microbial activity of the biofilm. The presence of TiO₂ NPs increases the surface binding energy between Cd²⁺ and functional groups such as carboxyl groups, enhancing the Cd²⁺ accumulation on the biofilm.