Affinity Directed Surface Functionalization of Two Different Metal Nanoparticles by a Natural Ionophore: Probing and Removal of Hg2+ and Al3+ Ions from Aqueous Solutions.

In this work, we report affinity controlled surface modifications of two different metal nanoparticles (MNPs) using a hydrophilic natural ionophore (microbial chelator) aeruginic acid (abbreviated as H2L) that possesses two different types of binding pockets viz. O/O from carboxylic acid group and N/O from a phenol-thiazole moiety. Preferred binding of the former donor set (i.e., O/O) on to the surface of silver nanoparticles (AgNPs) has resulted in a colorimetric nanomaterial HL@AgNPs, which showed naked eye observable easy detection of Hg2+ in aqueous HEPES buffer at pH 7.4, even in the presence of other metal ions. On the other hand, excellent affinity of the phenol-thiazole moiety (i.e., N/O) for iron nanosurfaces (FeNPs) develops a fluorogenic nanomaterial HL@FeNPs. Brilliant emission behavior of this nanomaterial enabled it to be useful for highly selective recognition of Al3+ under identical experimental conditions. Remarkable fluorescence enhancement (122-folds) of HL@FeNPs upon addition of Al3+ remain unchanged even in the presence of other competing metal ions. The nanomaterials HL@AgNPs and HL@FeNPs could even detect the target analytes instantly offering lower detection limits of 2 and 80 nM, respectively. Presence of toxic metal ions as environmental pollutant demands for dual-functional materials capable of performing the task of probing cum removal. Surface functionalizations of the nanomaterials of silver and iron with H2L have also resulted two removal agents that can efficiently and easily extract Hg2+ and Al3+ ions from contaminated water, respectively. We are not aware of any work that highlights the manifold utilization of a microbial chelator (i.e., natural ionophore) in the facile construction of different metal nanoparticles for environmental applications such as detection cum removal of toxic metal ions from aqueous solutions.

Removal of aluminium from aqueous solution by four wild-type strains of Aspergillus niger.

This paper provides a unique comparison of the performance of four wild-type Aspergillus niger strains in remediation of aluminium(III)-contaminated aqueous solutions. The direct fungal aluminium removal via biosorption and bioaccumulation was compared among all fungal strains, including bioaccumulation efficiency during dynamic and static cultivation. Our results indicate that aluminium bioaccumulation by living biomass outperformed biosorption, although biosorption by non-living biomass is a less time-demanding process. Among others, only one strain significantly differed regarding comparison of dynamic and static bioaccumulation. In this case, a significantly higher removal performance was achieved under dynamic cultivation conditions at initial aluminium(III) concentrations over 2.5 mg L-1. Although the fungal sensitivity towards aluminium(III) differed among selected fungal strains, there was no apparent correlation between the strains' removal performance and their adaptive mechanisms.

Use of high metal-containing biogas digestates in cereal production - Mobility of chromium and aluminium.

Biogas digestate use as organic fertilizer has been widely promoted in recent years as a part of the global agenda on recycling waste and new sustainable energy production. Although many studies have confirmed positive effects of digestates on soil fertility, there is still lack of information on the potential adverse effects of digestates on natural soil heavy metal content, metal leaching and leaching of other pollutants. We have investigated the release of aluminium (Al) and chromium (Cr) from different soils treated with commercial digestates high in mentioned potentially problematic metals in a field experiment, while a greenhouse and a laboratory column experiment were used to address mobility of these metals in two other scenarios. Results obtained from the field experiment showed an increase in total concentrations for both investigated metals on plots treated with digestates as well as a significant increase of water-soluble Al concentrations. Factors that were found to be mostly affecting the metal mobility were dissolved organic carbon (DOC), pH and type of soil. Metal binding and free metal concentrations were modelled using the WHAM 7.0 software. Results indicated that the use of digestates with high metal content are comparable to use of animal manure with respect to metal leaching. Data obtained through chemical modelling for the samples from the field experiment suggested that an environmental risk from higher metal mobility has to be considered for Al. In the greenhouse experiment, measured concentrations of leached Cr at the end of the growing season were low for all treatments, while the concentration of leached Al from digestates was higher. The high irrigation column leaching experiment showed an increased leaching rate of Cr with addition of digestates.

Recovery of Al, Cr and V from steel slag by bioleaching: Batch and column experiments.

Steel slag is a major by-product of the steel industry and a potential resource of technology critical elements. For this study, a basic oxygen furnace (BOF) steel slag was tested for bacterial leaching and recovery of aluminium (Al), chromium (Cr), and vanadium (V). Mixed acidophilic bacteria were adapted to the steel slag up to 5% (w/v). In the batch tests, Al, Cr, and V were bioleached significantly more from steel slag than in control treatments. No statistical difference was observed arising from the duration of the leaching (3 vs 6 d) in the batch tests. Al and Cr concentrations in the leachate were higher for the smaller particle size of the steel slag (<75 µm), but no difference was observed for V. In the column tests, no statistical difference was found for pH, Al, Cr and V between the live culture (one-step bioleaching) and the supernatant (two-step bioleaching). The results show that the culture supernatant can be effectively used in an upscaled industrial application for metal recovery. If bioleaching is used in the 170-250 million tonnes of steel slag produced per year globally, significant recoveries of metals (100% of Al, 84% of Cr and 8% of V) can be achieved, depending on the slag composition. The removal and recovery percentages of metals from the leachate with Amberlite®IRA-400 are relatively modest (<67% and <5%, respectively), due to the high concentration of competing ions (SO42-, PO43-) in the culture medium. Other ion exchange resins can be better suited for the leachate or methods such as selective precipitation could improve the performance of the resin. Further research is needed to minimise interference and maximise metal recovery.

Optimization of aluminium recovery from water treatment sludge using Response Surface Methodology.

For decades, water treatment plants in Malaysia have widely employed aluminium-based coagulant for the removal of colloidal particles in surface water. This generates huge amount of by-product, known as sludge that is either reused for land applications or disposed to landfills. As sludge contains high concentration of aluminium, both can pose severe environmental issues. Therefore, this study explored the potential to recover aluminium from water treatment sludge using acid leaching process. The evaluation of aluminium recovery efficiency was conducted in two phases. The first phase used the one factor at a time (OFAT) approach to study the effects of acid concentration, solid to liquid ratio, temperature and heating time. Meanwhile, second phase emphasized on the optimization of aluminium recovery using Response Surface Methodology (RSM). OFAT results indicated that aluminium recovery increased with the rising temperature and heating time. Acid concentration and solid to liquid ratio, however, showed an initial increment followed by reduction of recovery with increasing concentration and ratio. Due to the solidification of sludge when acid concentration exceeded 4 M, this variable was fixed in the optimization study. RSM predicted that aluminium recovery can achieve 70.3% at optimal values of 4 M, 20.9%, 90 °C and 4.4 h of acid concentration, solid to liquid ratio, temperature and heating time, respectively. Experimental validation demonstrated a recovery of 68.8 ±â€¯0.3%. The small discrepancy of 2.2 ±â€¯0.4% between predicted and validated recovery suggests that RSM was a suitable tool in optimizing aluminium recovery conditions for water treatment sludge.

Direct Observation of Hydrangea Blue-Complex Composed of 3-O-Glucosyldelphinidin, Al3+ and 5-O-Acylquinic Acid by ESI-Mass Spectrometry.

The blue sepal color of hydrangea is due to a metal complex anthocyanin composed of 3-O-glucosyldelphinidin (1) and an aluminum ion with the co-pigments 5-O-caffeoylquinic acid (2) and/or 5-O-p-coumaroylquinic acid (3). The three components, namely anthocyanin, Al3+ and 5-O-acylquinic acids, are essential for blue color development, but the complex is unstable and only exists in an aqueous solution. Furthermore, the complex did not give analyzable NMR spectra or crystals. Therefore, many trials to determine the detailed chemical structure of the hydrangea-blue complex have not been successful to date. Instead, via experiments mixing 1, Al3+ and 2 or 3 in a buffered solution at pH 4.0, we obtained the same blue solution derived from the sepals. However, the ratio was not stoichiometric but fluctuated. To determine the composition of the complex, we tried direct observation of the molecular ion of the complex using electrospray-ionization mass spectrometry. In a very low-concentration buffer solution (2.0 mM) at pH 4.0, we reproduced the hydrangea-blue color by mixing 1, 2 and Al3+ in ratios of 1:1:1, 1:2:1 and 1:3:1. All solution gave the same molecular ion peak at m/z = 843, indicating that the blue solution has a ratio of 1:1:1 for the complex. By using 3, the observed mass number was m/z = 827 and the ratio of 1, 3 and Al3+ was also 1:1:1. A mixture of 1, 3-O-caffeoylquinic acid (4) and Al3+ did not give any blue color but instead was purple, and the intensity of the molecular ion peak at m/z = 843 was very low. These results strongly indicate that the hydrangea blue-complex is composed of a ratio of 1:1:1 for 1, Al3+ and 2 or 3.

Detoxification of polluted marine sediments using water treatment sludge.

The purpose of this study was development of the optimal conditions for the inertization of the polluted marine sediments using groundwater treatment sludge highly enriched in iron and aluminum. For that purpose fine-grained sediment (>85% clay and silt fraction) highly enriched in copper and zinc was amended with the waste sludge (from 10% to 50%). The sample with the optimum percentage of the waste sludge was further subjected the thermal treatment at 200-800°C. The efficiency of the treatment was determined by the leaching tests and toxicity testing using Hordeum vulgare L. as biosystem. The percentage of the seed germination, the root elongation, and the germination index before and following the treatment were determined. Untreated sediment leachate caused significant arrest in the percentage of the seed germination (6.7 ± 6.7%), the root elongation (1.9 ± 2.2%), and the germination index (0.2 ± 0.3%) with EC50 of 24.9%, suggesting a significant toxic potential of the sediments. After amendment with 30% of the waste sludge the concentrations of the considered micropollutants decreased below regulated values while all three toxicological parameters showed no significant difference compared to the negative control. The toxicity of the sediment was completely removed following the thermal treatment at 400°C.

Changes in the fractionation profile of Al, Ni, and Mo during bioleaching of spent hydroprocessing catalysts with Acidithiobacillus ferrooxidans.

Spent hydroprocessing catalysts are known to contain a variety of potentially toxic metals and therefore studies on the bioavailability and mobility of these metals are critical for understanding the possible environmental risks of the spent catalysts. This study evaluates the different chemical fractions/forms of aluminium (Al), nickel (Ni), and molybdenum (Mo) in spent hydroprocessing catalyst and the changes they undergo during bioleaching with Acidithiobacillus ferrooxidans. In the spent catalyst (prior to bioleaching), Al was primarily present in its residual form, suggesting its low environmental mobility. However, Ni comprised mainly an exchangeable fraction, indicating its high environmental mobility. Molybdenum was mainly in the oxidizable form (47.1%), which indicated that highly oxidizing conditions were required to liberate it from the spent catalyst. During bioleaching the exchangeable, reducible and oxidizable fractions of all the metals were leached, whereas the residual fractions remained largely unaffected. At the end of bioleaching process, the metals remaining in the bioleached sample were predominantly in the residual fraction (98.3-99.5%). The 'risk assessment code' (RAC) and IR analysis also demonstrated that the environmental risks of the bioleached residue were significantly lower compared to the untreated spent catalyst. The results of this study suggest that bioleaching is an effective method in removing the metals from spent catalysts and the bioleached residue poses little environmental risk.

Evaluation of leached metals in recovered aluminum coagulants from water treatment slurry.

The water treatment industry consumes large quantities of coagulant and produces huge amounts of slurry. The cost of alum used in water treatment, stringent regulations and negative impacts of sludge disposal are the motive to do integrated research studies on the technical feasibility of aluminum coagulant recovery from sludge using acidification. This work studied the leaching of iron, manganese, and chromium as the most extracted metals with aluminum during sludge acidification; furthermore, these metals have a great impact on the recovered coagulants' efficiency and treated water quality. The sludge used was collected from El-Sheikh Zayd water treatment plant in Egypt, then dried and ground; afterward, the effect of acid concentration, sludge mass, temperature, mixing speed and mixing time was studied. In addition, it was noticeable that the efficiency of sulfuric acid in leaching iron, manganese and chromium is higher than that of hydrochloric acid. Also, higher leaching for the three metals was obtained in all the experiments using higher acid concentration, elevated temperature, and rotational speed. Finally, the leached metals in recovered aluminum coagulants will not limit its application to water and wastewater treatment, as their concentrations are still very low if compared with aluminum, even with the highest leaching efficiency.

Natural gas anodes for aluminium electrolysis in molten fluorides.

Industrial primary production of aluminium has been developed and improved over more than 100 years. The molten salt electrolysis process is still suffering from low energy efficiency and considerable emissions of greenhouse gases (CO2 and PFC). A new concept has been suggested where methane is supplied through the anode so that the CO2 emissions may be reduced significantly, the PFC emissions may be eliminated and the energy consumption may decrease significantly. Porous carbon anodes made from different graphite grades were studied in controlled laboratory experiments. The anode potential, the anode carbon consumption and the level of HF gas above the electrolyte were measured during electrolysis. In some cases it was found that the methane oxidation was effectively participating in the anode process.

A sustainable process for the recovery of valuable metals from spent lithium-ion batteries.

In this work, an eco-friendly and hydrometallurgical process for the recovery of cobalt and lithium from spent lithium-ion batteries has been proposed, which includes pretreatment, citric acid leaching, selective chemical precipitation and circulatory leaching. After pretreatment (manual dismantling, N-methyl pyrrolidone immersion and calcination), Cu and Al foils are recycled directly and the cathode active materials are separated from the cathode efficiently. Then, the obtained cathode active materials (waste LiCoO2) was firstly leached with 1.25 mol l(-1) citric acid and 1 vol.% H2O2 solution. Then cobalt was precipitated using oxalic acid (H2C2O4) under a molar ratio of 1:1.05 (H2C2O4: Co(2+)). After filtration, the filtrate (containing Li(+)) and H2O2 was employed as a leaching agent and the optimum conditions are studied in detail. The leaching efficiencies can reach as high as 98% for Li and 90.2% for Co, respectively, using filter liquor as leaching reagent under conditions of leaching temperature of 90°C, 0.9 vol.% H2O2 and a solid-to-liquid ratio of 60 ml g(-1) for 35 min. After three bouts of circulatory leaching, more than 90% Li and 80% Co can be leached under the same leaching conditions. In this way, Li and Co can be recovered efficiently and waste liquor re-utilization is achievable with this hydrometallurgical process, which may promise both economic and environmental benefits.

[Determination of residual aluminium Ion in Huoxiang Zhengqi pellets by GFAAS with EDTA complexation extraction].

To establish an EDTA complexation extraction pretreatment combining with GFAAS method for the determination of residual aluminium ion in Huoxiang zhengqi pellets without digestive treatment, systematical investigation was made on sample preparation, and EDTA was used for the complexation extraction of residual aluminium ion in samples. The pH, concentration and volume of extraction solution, the temperature and time of microwave extraction, and graphite furnace temperature program were investigated. The results were compared with the microwave digestion. It was showed that, 0.1 g of sample weight was added in 20 mL 0.05 mol x L(-1) EDTA solution (pH 3.5), followed by heating at 150 degrees C for 10 min in the microwave extraction device. The determination of GFAAS was performed at optimized detection wavelength (257.4 nm) as well as graphite furnace temperature program, the detection limits and quantification limits were 2.37 µg x L(-1) and 7.89 µg x L(-1), respectively. The precision (RSD) was less than 2.3%. The average recovery was 96.9% -101%. The present method is easy, rapid and accurate for the determination of residual aluminium ion in Huoxiang zhengqi pellets.

Effective alleviation of aluminum phytotoxicity by manure-derived biochar.

The alleviation of aluminum phytotoxicity to wheat plants in a hydroponic system through the amendment of biochar is investigated to explore the possibility of applying biochar in acidic soil amelioration. Biochar derived from cattle manure pyrolyzed at 400 °C (CM400) and the CM400 biochar washed with distilled-deionized water to remove alkalinity (WCM400) were prepared to determine the roles of the liming effect and adsorption during the alleviation of Al toxicity. Upon addition of 0.02% (W/V) CM400 to the exposure solution, the inhibition of plant growth by Al was significantly reduced while the toxic threshold was extended from 3 to 95 µmol/L Al(3+). Due to the biochar liming effect, the aluminum species were converted to Al(OH)(2+) and Al(OH)2(+) monomers, which were strongly adsorbed by biochar; furthermore, the highly toxic Al(3+) evolved to less toxic Al(OH)3 and Al(OH)4(-) species. Adsorption of Al by the biochar is dominated by surface complexation of the carboxyl groups with Al(OH)(2+)/Al(OH)2(+) rather than through electrostatic attraction of Al(3+) with negatively charged sites. Compared to the liming effect, the adsorption by biochar exhibited a sustainable effect on the alleviation of Al toxicity. Therefore, the biochar amendment appears to be a novel approach for aluminum detoxification in acidic soils.

Approaches to improve separation efficiency of eddy current separation for recovering aluminum from waste toner cartridges.

Separation efficiency of eddy current separation (ECS) is low (about 85%) in industrial application for recovering aluminum from crushed waste toner cartridges. Influencing factors of ECS were studied to improve the separation efficiency. Operation factors were researched by orthogonal experiment of ECS on investigating the separation distance between aluminum and plastic flakes. The results indicated the difference (ωR-v) between feeding speed (v) and rotation speed (ω) of magnetic drum (radius: R) was critical factor of influencing the separation efficiency, feeding speed (v) was general factor, and collecting position (H) was subordinate factor. Separation efficiency decreased as the increasing of v, and increased as the increasing of (ωR-v). 0.9 m was the optimal value of H in the orthogonal experiment. Influencing factors of particle characteristics and machine structure were studied by newly established models for computing the separation distance between aluminum and plastic flake in ECS. The results indicated changing of particle size would influence the separation efficiency greater than ω and particle shape. Separation efficiency will increase as the increasing of particle size and ω. Shape of circle is beneficial to improve separation efficiency. Finally, approaches to improve separation efficiency of ECS were presented.

Aluminum and sulphate removal by a highly Al-resistant dissimilatory sulphate-reducing bacteria community.

A highly Al-resistant dissimilatory sulphate-reducing bacteria community was isolated from sludge of the wetland of Urgeiriça mine (community W). This community showed excellent sulphate removal at the presence of Al³âº. After 27 days of incubation, 73, 86 and 81% of sulphate was removed in the presence of 0.48, 0.90 and 1.30 mM of Al³âº, respectively. Moreover, Al³âº was simultaneously removed: 55, 85 and 78% of metal was removed in the presence of 0.48, 0.90 and 1.30 mM of Al³âº, respectively. The dissociation of aluminium-lactate soluble complexes due to lactate consumption by dissimilatory sulphate-reducing bacteria can be responsible for aluminum removal, which probably precipitates as insoluble aluminium hydroxide. Phylogenetic analysis of 16S rRNA gene showed that this community was mainly composed by bacteria closely related to Desulfovibrio desulfuricans. However, bacteria affiliated to Proteus and Ralstonia were also present in the community.

Purification of sulphate leach liquor of spent Raneynickel catalyst containing Al and Ni by solvent extraction with organophosphorus-based extractants.

Solvent extraction (SX) separation of Al from Ni sulphate leach liquor (LL) of spent Raneynickel catalyst containing 0.12 M Al and 1.448 M Ni using organophosphorus extractants has been investigated. Optimization of process conditions includes aqueous pH, extractant concentration, phase ratio, and stripping. Comparison of Al extraction efficiency with 0.45 M extractant concentration for TOPS 99, PC 88 A, and Cyanex 272 at an equilibrium pH of 2.23 was 81.8%, 98.6%, and 75%, respectively. The corresponding coextraction of Ni was 0.65, 0.6, and 0.9. Among the three extractants screened, PC 88A showed better extraction efficiency for Al at lower pH values than the others. Using 0.45 M PC 88 A, extraction isotherm was obtained at an aqueous-to-organic (A : O) phase ratio of 1 : 1-3 and O : A ratio of 1 : 1-5, which predicted possible separation of Al in 2 stages at A/O ratio of 2. Quantitative stripping was achieved by H(2)SO(4).

Can hazardous waste become a raw material? The case study of an aluminium residue: a review.

The huge number of research studies carried out during recent decades focused on finding an effective solution for the waste treatment, have allowed some of these residues to become new raw materials for many industries. Achieving this ensures a reduction in energy and natural resources consumption, diminishing of the negative environmental impacts and creating secondary and tertiary industries. A good example is provided by the metallurgical industry, in general, and the aluminium industry in this particular case. The aluminium recycling industry is a beneficial activity for the environment, since it recovers resources from primary industry, manufacturing and post-consumer waste. Slag and scrap which were previously considered as waste, are nowadays the raw material for some highly profitable secondary and tertiary industries. The most recent European Directive on waste establishes that if waste is used as a common product and fulfils the existing legislation for this product, then this waste can be defined as 'end-of-waste'. The review presented here, attempts to show several proposals for making added-value materials using an aluminium residue which is still considered as a hazardous waste, and accordingly, disposed of in secure storage. The present proposal includes the use of this waste to manufacture glass, glass-ceramic, boehmite and calcium aluminate. Thus the waste might effectively be recovered as a secondary source material for various industries.

Potential release of aluminum and other metals by food-grade aluminum foil used for skin allograft cryo preservation.

Since 1991, the skin bank of the Queen Astrid Military Hospital uses food-grade aluminum foil as a primary support for storing cryo preserved human donor skin (511 donors). The possible release of heavy metals into the cryo preservation media (30% (v/v) glycerol in physiological water) and the possible impact this release could have on the quality of the cryo preserved donor skin was evaluated. Aluminum was the principal detection target. Possible contaminants of the aluminum foil as such (arsenic, cadmium, chromium and lead) were also investigated. The evaluation was set up after a Belgian Competent Authority inspection remark. Aluminum was detected at a concentration of 1.4 mg/l, arsenic and lead were not detected, while cadmium and chromium were detected in trace element quantities. An histological analysis revealed no differences between cryo preserved and fresh donor skin. No adverse reactions in patients, related to the presence of aluminum or heavy metal traces, were reported since the introduction of the cryo preserved donor skin in our burn wound centre.

Recovery of phosphorus and aluminium from sewage sludge ash by a new wet chemical elution process (SESAL-Phos-recovery process).

The potential of a new wet chemical process for phosphorus and aluminium recovery from sewage sludge ash by sequential elution with acidic and alkaline solutions has been investigated: SESAL-Phos (sequential elution of sewage sludge ash for aluminium and phosphorus recovery). Its most innovative aspect is an acidic pre-treatment step in which calcium is leached from the sewage sludge ash. Thus the percentage of alkaline soluble aluminium phosphates is increased from 20 to 67%. This aluminium phosphate is then dissolved in alkali. Subsequently, the dissolved phosphorus is precipitated as calcium phosphate with low heavy metal content and recovered from the alkaline solution. Dissolved aluminium is recovered and may be reused as a precipitant in wastewater treatment plants.

Nanographene oxide modified phenyl methanethiol nanomagnetic composite for rapid separation of aluminum in wastewaters, foods, and vegetable samples by microwave dispersive magnetic micro solid-phase extraction.

A new method based on graphene oxide modified (4-phenyl) methanethiol nanomagnetic composite (Fe3O4@4-PhMT-GO) was used for extraction and separation of aluminum from wastewater, food, and vegetable samples in aluminum cookware by microwave dispersive magnetic micro solid-phase extraction (MDM-µ-SPE). In optimized conditions, the working range (WR), the linear range (LR), the limit of detection (LOD), and enrichment factor (EF) were obtained 5-5200 µg L-1, 5-1600 µg L-1, 1.5 µg L-1, and 48.8, respectively (RSD% = 2.5). By MDM-µ-SPE procedure, the aluminum concentrations in baking rice and spinach with aluminum cookware were obtained 97.43 ± 2.57 mg g-1 and 131.64 ± 5.18 mg g-1, respectively which was analyzed by atom trap flame atomic absorption spectrometer (AT-FAAS). The results showed, the aluminum concentrations in cooked foods with Teflon cookware were less than aluminum cookware. The methodology was validated by standard reference materials (SRM) and inductively coupled plasma mass spectrometry analysis (ICP-MS).