Kinetic Modeling of Cr(VI) Reduction by nZVI in Soil: The Influence of Organic Matter and Manganese Oxide.

The effect of soil composition on the reduction of hexavalent chromium (Cr(VI)) by zero valent iron nanoparticles was studied. A model was proposed, to investigate both the effect of manganese oxide and the simultaneous effect of manganese dioxide and soil organic matter on the kinetic of Cr(VI) reduction. Fe(0) nanoparticles consumption by the reaction with dissolved oxygen, water and soluble Cr(VI) was taken into account. The model was validated through experimental tests performed on soil samples collected at an industrial polluted site, and on artificially contaminated samples from the same site, in the presence of selected amount of leonardite.

Kinetic Study of Nitrate Removal from Aqueous Solutions Using Copper-Coated Iron Nanoparticles.

Nitrates are considered hazard compounds for human health due to their tendency to be reduced to nitrites, in particular in reducing environment. Nano zero valent iron (nZVI) represents an efficient and low-cost adsorbent/reductive agent for nitrate removal from groundwater and wastewaters and a little addition of a second metal species (Cu, Pd, Ni, Ag) has proven to increase process effectiveness, by enhancing stability and oxidation resistance of nanoparticles. In this work Cu/Fe nanoparticles were loaded in a NO3- solution (100 mg L-1) and the removal efficiency was tested by monitoring nitrate concentration at selected time intervals. Results showed that the nitrate removal process involves both reduction and adsorption processes: the removal mechanism has been investigated, and the pseudo-first-order and pseudo-second-order-adsorption kinetic models were successfully tested.

Environmental effects of using chelating agents in polluted sediment remediation.

The results of laboratory scale experimental tests of contaminant extraction from marine sediment slurries are presented and discussed. The objective of this study was to compare the effectiveness of EDTA and rhamnolipid in copper removal from an artificially contaminated sediment. The comparison was made in terms of metal extraction yield, and in the evaluation of its mobilization towards the more exchangeable fractions in the sediment. Results show that, under acidic conditions established during washing, EDTA ensured higher extractions efficiencies of Cu (up to 95 %) than rhamnolipid, although there was less mobilization into bioavailable forms with the use of rhamnolipid. In addition, in the view of a biological treatment of the spent solution, the use of rhamnolipid resulted in a lower decrease of the specific oxygen uptake rate with respect to EDTA. In fact, the low surfactants concentration required, partially compensated the toxic effect of Cu towards biomass.

Tetrachloroethene recovery and hazard reduction of spent powders from dry cleaning process.

Dry cleaning facilities using perchloroethylene produce a solid waste consisting of spent filtering powders with a high content of residual perchloroethylene, together with dyes and non-volatile residues. Untreated spent powders, classified as hazardous waste, cannot be disposed in landfill and incineration represents the only viable alternative. In this study, together with a full characterisation of the waste, the removal and recovery of the residual perchloroethylene by means of different heat treatments was investigated. In particular, tests of distillation and stripping with air and steam were carried out, evaluating the effectiveness of the treatments by quantifying the residual perchloroethylene in the samples treated. The results obtained show that the spent filtering powders contained about 25% wt. of perchloroethylene and that the maximum perchloroethylene recovery was obtained by steam stripping; approximately 98% after only 50 minutes. However, this treatment accounted for the production of a liquid mixture containing perchloroethylene and of a solid waste that required a further washing with boiling water to decrease the residual organic content below the eligibility criteria for landfill disposal.

Titanium Dioxide Nanoparticles Doped with Iron for Water Treatment via Photocatalysis: A Review.

Iron-doped titanium dioxide nanoparticles are widely employed for photocatalytic applications under visible light due to their promising performance. Nevertheless, the manufacturing process, the role of Fe3+ ions within the crystal lattice of titanium dioxide, and their impact on operational parameters are still a subject of controversy. Based on these assumptions, the primary objective of this review is to delineate the role of iron, ascertain the optimal quantity, and elucidate its influence on the main photocatalysis parameters, including nanoparticle size, band gap, surface area, anatase-rutile transition, and point of zero charge. Moreover, an optimized synthesis method based on comprehensive data and insights from the existing literature is proposed, focusing exclusively on iron-doped titanium oxide while excluding other dopant variants.

Functionalized biochar from waste as a slow-release nutrient source: Application on tomato plants.

Licorice processing waste was pyrolyzed at different temperatures (500 and 700 °C) to obtain biochar (BC500 and BC700) for use as a slow-release fertilizer on Solanum lycopersicum. The materials were characterized through BET analysis, SEM, elemental analysis, pHzc, and pyrolysis temperature effect was evaluated. The biochars were functionalized by the impregnation method to enrich them with nitrogen, phosphorus, and potassium (NPK), and desorption tests were performed in aqueous solution at different pHs (5 and 7). The pseudo-second-order model described well the release of all 3 macronutrients tested, BC500 was found to have slower release kinetics due to smaller pore size, reaching adsorption/desorption equilibrium after 14 days, compared with 10 for BC700, Kdes were lower in all 3 cases and NPK content was higher, initial pH did not change the release kinetics. BC500 was selected as an agricultural soil conditioner by testing at both different dosages of BC (0-25 %) and different NPK ratios (3:1:4 and 4:1:3). The treatment significance was evaluated. The best treatment resulted in BC dosage of 25 % nutrient ratio 4:1:3 which increased, compared to the control, total chlorophyll content (+38 %) and carotenoids (+15 %).

Removal of Methylene Blue from Wastewater by Waste Roots from the Arsenic-Hyperaccumulator Pteris vittata: Fixed Bed Adsorption Kinetics.

Phytoremediation of arsenic-contaminated water was successfully conducted by means of the perennial fern Pteris vittate, which is an arsenic-hyperaccumulator plant able to grow in hydroponic cultures. In order to avoid the costs linked to the disposal of As-contaminated biomass, in this work, Pteris vittata waste roots were tested as a low-cost bio-adsorbent for the removal of methylene blue (MB) from water in a fixed-bed adsorption configuration. As a matter of fact, methylene blue can negatively impact the growth and health of algae and plants by blocking light from reaching them in water, which can alter their normal biological processes. Previous works have already shown the potentiality of such material toward the uptake of methylene blue; however, all the studies conducted were just focused on batch-mode experiments. In this work, column runs were carried out at 20 °C, evaluating the bed void fraction for each test and hence estimating the apparent density of the material (300 g/L). The breakthrough curves collected were fitted by means of a mathematical model based on the linear driving force (LDF) approximation to obtain information on the mass transfer mechanism occurring in the system. A relation for the product between the LDF mass transfer coefficient and the solid specific surface (kLDFas) with respect to the Reynolds (Re) dimensionless number was obtained (kLDFas=0.45Re). The range of validity of such expression was Re<0.025. Its applicability was deeply discussed: in such conditions, the technology is ready to be tested at larger scales.

New Materials and Technologies for Durability and Conservation of Building Heritage.

The increase in concrete structures' durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings.

Effect of Water-Ethanol Extraction as Pre-Treatment on the Adsorption Properties of Aloe vera Waste.

The adsorption properties of Aloe vera (Aloe barbadensis Miller) for the uptake of Methylene Blue (MB) from water were investigated after pre-treating the material with water-ethanol solutions at different ethanol concentrations: 0% v/v (AV0), 25% v/v (AV25), and 50% v/v (AV50). The pre-treated materials were characterized as follows: the pHZC was evaluated to be 6, 5.7, and 7.2 for AV0, AV25, and AV50, respectively; from BET-BJH analysis the mesoporous nature of the material and an increase from 108.2 (AV0) to 331.7 (AV50) m2/kg of its solid surface area was observed; TG analysis revealed a significat increase in volatile compounds from the untreated (5.4%) to the treated materials (8.9%, 10.3%, and 11.3% for AV0, AV25, and AV50, respectively). Adsorption batch tests were then performed to investigate the equilibrium, the kinetics, and the thermodynamics of the process. Results suggested that the Langmuir model was in agreement with the experimental results, and values for qmax of 199 mg/g, 311 mg/g, and 346 mg/g were calculated for AV0, AV25, and AV50, respectively. The kinetic results were used to develop a mathematical model to estimate the effective diffusion coefficient for each type of Aloe adopted. Effective diffusion coefficients of 5.43·10-7 cm2/min, 3.89·10-7 cm2/min, and 5.78·10-7 cm2/min were calculated for AV0, AV25, and AV50, respectively. It was found that pre-treatment, on the one hand, enhances the adsorption capacity of the material and on the other, reduces its affinity toward MB uptake.

Functionalization of Commercial Electrospun Veils with Zinc Oxide Nanostructures.

The present research is focused on the synthesis of hexagonal ZnO wurtzite nanorods for the decoration of commercially available electrospun nylon nanofibers. The growth of ZnO was performed by a hydrothermal technique and for the first time on commercial electrospun veils. The growth step was optimized by adopting a procedure with the refresh of growing solution each hour of treatment (Method 1) and with the maintenance of a specific growth solution volume for the entire duration of the treatment (Method 2). The overall treatment time and volume of solution were also optimized by analyzing the morphology of ZnO nanostructures, the coverage degree, the thermal and mechanical stability of the obtained decorated electrospun nanofibers. In the optimal synthesis conditions (Method 2), hexagonal ZnO nanorods with a diameter and length of 53.5 nm ± 5.7 nm and 375.4 nm ± 37.8 nm, respectively, were obtained with a homogeneous and complete coverage of the veils. This easily scalable procedure did not damage the veils that could be potentially used as toughening elements in composites to prevent delamination onset and propagation. The presence of photoreactive species makes these materials ideal also as environmentally friendly photocatalysts for wastewater treatment. In this regard, photocatalytic tests were performed using methylene blue (MB) as model compound. Under UV light irradiation, the degradation of MB followed a first kinetic order data fitting and after 3 h of treatment a MB degradation of 91.0% ± 5.1% was achieved. The reusability of decorated veils was evaluated and a decrease in photocatalysis efficiency was detected after the third cycle of use.

Remediation of hexavalent chromium contaminated water through zero-valent iron nanoparticles and effects on tomato plant growth performance.

Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study aimed to evaluate the Cr(VI) removal by zero valent iron nanoparticles (nZVI) reduction process and the impact of Cr(VI), nZVI and combined treatment with nZVI and Cr(VI) on tomato growth performance. To evaluate the Cr(VI) toxic effect on germination capability, seeds were exposed to increasing Cr(VI) concentrations up to 1000 mg L-1. The inhibition of seed germination and the decrease of hypocotyl and root length started from Cr(VI) 5 mg L-1. Under treatment with Cr(VI) + nZVI 5 mg L-1, seed germination, hypocotyl and root length resulted significantly higher compared to Cr(VI) 5 mg L-1 treatment. The impact of only nZVI was investigated on chlorophyll and carotenoid in leaves; iron levels in leaves, roots, fruits and soil; carotenoid, fat-soluble vitamin and nicotianamine in mature fruits. A significant increase of leaf chlorophyll and carotenoids was observed after nZVI 5 mg L-1 treatment compared to controls. No significant variations were observed in carotenoids, fat-soluble vitamins and nicotianamine levels after treatment with nZVI 5 mg L-1 in mature fruits. For their ability to reduce Cr(VI) and to stimulate tomato growth, nZVI might to be considered as alternative for remediation purposes.

A physical-based interpretation of mechanism and kinetics of Cr(VI) reduction in aqueous solution by zero-valent iron nanoparticles.

The aim of this paper is to show the results obtained by investigating the reduction of hexavalent Chromium [Cr(VI)] by iron nano-particles in aqueous solution, interpreted in light of the particle-grain model. The diffusional and geometric parameters that govern and describe the reacting system were estimated from the evidences deriving from the characterization and the experiments conducted, allowing assumptions based on physical principles. Such procedure rendered the particle-grain model a valid choice for the interpretation of the results obtained. The model, used in its dimensionless form, was tested according to a preliminary procedure aimed at analyzing the sensitivity of the system, by varying within wide ranges the ratio between the reaction rate, the diffusive mass transfer rate, and the particle-grain radius, to show how reliable its potential application may be. Subsequently, a non-linear regression procedure was used to estimate the two main parameters of the model that affect the reduction process: (i) the diffusion coefficient within the solid layer produced along with the reaction, Dpc (6.02 E-13 m2 s-1), and (ii) the kinetic constant of the surface reaction, kc (0.21 m s-1). The values found for the parameters were perfectly in line with theoretical considerations and experimental evidences.

Synthesis of Fe/Ni Bimetallic Nanoparticles and Application to the Catalytic Removal of Nitrates from Water.

This work investigated the effectiveness of zerovalent iron and Fe/Ni bimetallic nanoparticles in the treatment of water polluted by a high concentration of nitrates. Nanoparticle synthesis was carried out by a sodium borohydride reduction method in the presence of sodium oleate as a surfactant. The particles were characterized by XRD and SEM. Batch experiments were conducted on water samples contaminated by 300 mg L-1 of nitrate. The parameters investigated were the Fe/Ni dosage (0.05, 0.1, 0.2, 0.3, and 0.4 g L-1) and the reaction pH (unbuffered; buffered at pH = 3; initial pH = 3, 5, and 10). The results showed that almost complete nitrate removal (>99.8%) was always achieved after 15 min at a concentration of bimetallic nanoparticles higher than 0.2 g L-1. The optimization of bimetallic nanoparticle dosage was carried out at a fixed pH. Kinetic study tests were then performed at different temperatures to assess the effect of temperature on the nitrate removal rate. By fixing the pH at acidic values and with an operating temperature of 303 K, nitrates were completely removed after 1 min of treatment.

Process Intensification Techniques for the Production of Nano- and Submicronic Particles for Food and Medical Applications.

BACKGROUND: Nowadays, nanoparticles are of great interest for the industry due to their numerous possible applications in several fields. Research on this topic seeks to develop many procedures to produce nanoparticles, mostly at lab scale, batch-wise and with low yield. These procedures generally do not suit industrial needs of continuous, high capacity production. Moreover, the product characteristics require targeting narrow particle size distributions and high quality, which is difficult to achieve by traditional equipment. METHODS: Process intensification techniques aim to minimize plant size of continuous, high yield equipment capable to produce specific sized, high quality nanoparticles, combined with an increase in energy efficiency, safety and cost reduction. DISCUSSION: This paper reviews some adopted Process Intensification (PI) techniques for nanoparticles synthesis processes employed in the food and pharmaceutical sector. CONCLUSION: By reducing the technology transfer gap, nanotechnologies may become convenient and feasible, allowing both industries to achieve the production of higher quality products with particular characteristics without sensibly increasing additional costs. This will represent in the next future a strategic key feature of industries in the global market.

Nanomaterials application for heavy metals recovery from polluted water: The combination of nano zero-valent iron and carbon nanotubes. Competitive adsorption non-linear modeling.

Carbon Nanotubes (CNTs) and nano Zero-Valent Iron (nZVI) particles, as well as two nanocomposites based on these novel nanomaterials, were employed as nano-adsorbents for the removal of hexavalent chromium, selenium and cobalt, from aqueous solutions. Nanomaterials characterization included the determination of their point of zero charge and particle size distribution. CNTs were further analyzed using scanning electron microscopy, thermogravimetric analysis and Raman spectroscopy to determine their morphology and structural properties. Batch experiments were carried out to investigate the removal efficiency and the possible competitive interactions among metal ions. Adsorption was found to be the main removal mechanism, except for Cr(VI) treatment by nZVI, where reduction was the predominant mechanism. The removal efficiency was estimated in decreasing order as CNTs-nZVI > nZVI > CNTs > CNTs-nZVI* independently upon the tested heavy metal. In the case of competitive adsorption, Cr(VI) exhibited the highest affinity for every adsorbent. The preferable Cr(VI) removal was also observed using binary systems of the tested metals by means of the CNTs-nZVI nanocomposite. Single species adsorption was better described by the non-linear Sips model, whilst competitive adsorption followed the modified Langmuir model. The CNTs-nZVI nanocomposite was tested for its reusability, and showed high adsorption efficiency (the qmax values decreased less than 50% with respect to the first use) even after three cycles of use.

Binders alternative to Portland cement and waste management for sustainable construction-part 1.

This review presents "a state of the art" report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1-the present paper-focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Binders alternative to Portland cement and waste management for sustainable construction - Part 2.

The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

Experimental in situ chemical peroxidation of atrazine in contaminated soil.

Lab-scale experiments of in situ chemical oxidation (ISCO), were performed on soil contaminated with 100 mg kg(-1) of atrazine (CIET). The oxidant used was hydrogen peroxide catalysed by naturally occurring minerals or by soluble Fe(II) sulphate, added in aqueous solution. The oxidation conditions were: CIET:H2O2=1:1100, 2 PV or 3 PV reaction volume, Fe(II):H2O2=0, 1:22, 1:11. Stabilized (with KH2PO4 at a concentration of 16 g l(-1)) or non-stabilized hydrogen peroxide was used. The pH of the reagents was adjusted to pH=1 with sulphuric acid, or was not altered. Results showed that the addition of soluble Fe(II) increased the temperature of the soil slurry and the use of stabilized hydrogen peroxide resulted in a lower heat generation. The treatment reduced the COD of the soil of about 40%, pH was lowered and natural organic matter became less hydrophobic. The highest atrazine conversion (89%) was obtained in the conditions: 3 PV, Fe(II):H2O2=1:11 with stabilized hydrogen peroxide added in two steps. The stabilizer only increased H2O2 life-time significantly when soluble Fe(II) was added. Results indicate as preferential degradation pathway of atrazine in soil dechlorination instead of dealkylation.

Production of aggregate from non-metallic automotive shredder residues.

In this paper, the results of an experimentation on the production of granules suitable to be used as aggregates in cementitious or asphalt mixes are presented and discussed. The granules were obtained by granulating the non-metallic fraction of automotive shredder residues. In a preliminary separation step the fluff fraction containing mainly inert and non-metallic materials was sieved and analyzed for the metal content. In the following granulation step, the sieved fraction was mixed with binding materials, fly ash and a densifier agent, to produce granules of 5-30 mm of diameter and up to 1400 kg/m3 of specific weight. The granulation was carried out at room temperature in a rotating tank. Concrete samples prepared using as aggregates the produced granules showed a specific weight up to 1800 kg/m3 and a compressive strength up to about 55% of reference samples prepared using a calcareous aggregate, depending on the fluff content of the mixes, and on the nature of the binder and of the other components used.