HEAVY METALS REMOVAL FROM AQUEOUS SOLUTIONS USING TiO2, MgO,AND Al2O3 NANOPARTICLES

This study investigated the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ from aqueous solutions using nanoparticle sorbents (TiO₂, MgO, and Al₂O₃) with a range of experimental approaches. The maximum uptake values (sum of four metals) with multiple component solutions were 594.9, 114.6, and 49.4 mg g^?1, for MgO, Al₂O₃, and TiO₂, respectively. The sorption equilibrium isotherms were described using the Freundlich and Langmuir models. The best interpretation for experiment data was given by the Freundlich model for Cd²⁺, Cu²⁺, and Ni²⁺ in single- and multiple-component solutions. A first-order kinetic model adequately described the experimental data using MgO, Al₂O₃, and TiO₂. SEM-EDX both before and after metal sorption and soil solution saturation indices (SI) in MgO nanoparticles indicated that the main sorption mechanism for heavy metals was attributable to adsorption and precipitation, whereas heavy metal sorption by TiO₂ and Al₂O₃ adsorbents was due to adsorption. These nanoparticles may potentially be used as efficient sorbents for heavy metal removal from aqueous solutions. MgO nanoparticles were the most promising sorbents because of their high metal uptake.     

Adsorption of Pb2+ on Chitosan Cross‐Linked with Triethylene‐Tetramine

A novel triethylene‐tetramine cross‐linked chitosan (CCTS) was synthesized via the cross‐linking of triethylene‐tetramine and epichlorohydrin activated chitosan. Its structure was characterized by elemental analysis, infrared spectroscopy and X‐ray diffraction analysis, and the surface topography was determined with ESEM. The results were in agreement with expectations. The capacity of CCTS to adsorb Pb²⁺ ions from aqueous solutions was examined, and equilibrium and kinetic investigations were undertaken. The adsorption isotherms were fitted well by the Langmuir equation (R > 0.999). The maximum adsorbed amount, at pH 5.5, with an initial concentration of 3 mmol/L (621 ppm), was 378.8 mg/g. The adsorption process could be best described by a second‐order equation (R = 1). This suggests that the rate‐limiting step may be the chemical adsorption (chemisorption) step and not the mass transport. The separation factor used was 0 < R_L < 1. Therefore, it can be concluded that CCTS is an effective adsorbent for the collection of Pb²⁺.     

Usage of the sol–gel process on the fabrication of macroporous adsorbent activated-gamma alumina spheres

In this work, we have developed a chemical process to agglomerate activated-gamma alumina microparticles. It is based on the sol–gel process. The process which was developed preserves the characteristics of porosity of the alumina microparticles. It allows us to obtain dried spheres with or without the introduction of a biomass type MDF (medium density fiberboard) with the following characteristics: medium diameter between 2.5 and 3.3 mm; narrow diameter range; high sphericity (0.90); high mechanical resistance (0.04 kg f/sphere); high specific surface area (257 m²/g); a network of micropores, mesopores and macropores which connects the surface and the core of the adsorbent sphere. It also allows us to obtain adsorbent alumina spheres with displaced core from the shallowest layers or even completely hollow. The possibility to add increasingly higher adsorbents biomass contents makes this process cheaper to fabricate adsorbent spheres. Besides that preliminary tests of adsorption show that dried spheres with and without MDF reach, respectively, an efficiency of removing Cd/Cu/Zn/As of 30.9%/13.5%/59.9%/43.9% and 71.3%/24.9%/48.4%/43.7%. All of these described characteristics suggest that the present method produces a good adsorbent for heavy metals and arsenic.     

Thermal Effects During the Absorption of CO2 in Aqueous Solutions of 3‐Amino‐1‐Propanol

In this work, we study the process of CO₂ absorption, at high partial pressures, in aqueous solutions of 3‐amino‐1‐propanol (AP), with respect to the thermal effects of this operation. All of the experiments were performed in a stirred tank gas‐liquid reactor with a flat, known interface. The variables considered were the AP concentration in the range of 0.1 to 3.0 M and the temperature within the interval of 288–313 K. From the results, we deduce that the process takes place in the instantaneous nonisothermal regime, and we propose an equation which relates the experimental results of molar flux with the initial amine concentration. At the same time, we can evaluate the temperature increase at the gas‐liquid interface.     

New Regeneration Process of Heavy‐Metal‐Loaded Chelating Resins

An alternative to the classical acid‐base regeneration of chelating resins loaded with heavy metals is investigated. The new process consists in recovering the heavy metals with recyclable soluble complexing agents. The semiclosed reactor includes a fixed bed and a stirred tank. A three‐parameter model, which implies a double equilibrium in series, is introduced. When less than 10 % of the metal is still fixed on the resin at the end of the desorption, a simplified form of the model with two parameters, which describes a quick equilibrium followed by a first‐order kinetics reaction, is proposed. Both forms of the model can simulate results for different experimental conditions (polymer and metal types, polymer initial concentration). It was observed for both cases that the first equilibrium constant depends on the polymer type and that the rate constant of desorption depends on the metal type. The scale‐up of desorption is then conducted at mini‐pilot scale. Scale‐up criteria tend to minimize the desorption time and the soluble polymer quantity used.     

Thermally Resistive Electrospun Composite Membranes for Low‐Grade Thermal Energy Harvesting

In this work, thermally insulating composite mats of poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) blends are used as the separator membranes. The membranes improve the thermal‐to‐electrical energy conversion efficiency of a thermally driven electrochemical cell (i.e., thermocell) up to 95%. The justification of the improved performance is an intricate relationship between the porosity, electrolyte uptake, electrolyte uptake rate of the electrospun fibrous mat, and the actual temperature gradient at the electrode surface. When the porosity is too high (87%) in PAN membranes, the electrolyte uptake and electrolyte uptake rate are significantly high as 950% and 0.53 µL s^?1, respectively. In such a case, the convective heat flow within the cell is high and the power density is limited to 32.7 mW m^?2. When the porosity is lesser (up to 81%) in PVDF membranes, the electrolyte uptake and uptake rate are relatively low as 434% and 0.13 µL s^?1, respectively. In this case, the convective flow shall be low, however, the maximum power density of 63.5 mW m^?2 is obtained with PVDF/PAN composites as the aforementioned parameters are optimized. Furthermore, multilayered membrane structures are also investigated for which a bilayered architecture produces highest power density of 102.7 mW m^?2.     

Use of Functionalized Metallocene Copolymers from Ethylene and Polar Olefins as Compatibilizers for Low‐Density‐Polyethylene/Starch and Low‐Density‐Polyethylene/Dextran Blends

Summary: Functionalized metallocene copolymers synthesized from ethylene with 5‐hexen‐1‐ol and ethylene with 10‐undecen‐1‐ol were used as compatibilizers in LDPE/starch and LDPE/dextran blends in order to improve the interfacial adhesion between hydrophobic LDPE and hydrophilic natural polymers. An increase in tensile modulus and a slight decrease in tensile strength was observed when poly[ethylene‐co‐(10‐undecen‐1‐ol)] was added to a 70:30 wt.‐% LDPE/dextran blend, whereas the addition of poly[ethylene‐co‐(5‐hexen‐1‐ol)] as compatibilizer resulted in obtaining a more rigid material with a slightly higher modulus. Scanning electron microscopy of modified dextran blends containing 3 wt.‐% of both compatibilizers showed some degree of phase cocontinuity. Enhanced interfacial adhesion and decrease in particle size of starch was observed when 5 wt.‐% of poly [ethylene‐co‐(5‐hexen‐1‐ol)] copolymer was used as the compatibilizer in starch blends. The crystallization temperature of LDPE, determined by DSC, was shifted to a slightly higher temperature as a consequence of the addition of the compatibilizers. The existence of phase segregation was also revealed by thermal analysis when 5 wt.‐% of the copolymers were used as blend modifiers.

SEM micrograph of 70:30 wt.‐% LDPE/dextran blend with added poly[ethylene‐co‐(5‐hexen‐1‐ol)] compatibilizer.     

Investigation of Heavy Metal Release during Thermal Waste Treatment on a Forward‐Acting Grate by Means of Radiotracers

This paper deals with the determination of location, time and quantity of the release of heavy metals in a pilot‐scale grate system by means of short‐lived radioactive isotopes during the incineration of municipal waste. The isotopes ^69mZn (half life: 13.8 hours) and ⁶⁴Cu (half life: 12.7 hours) were used to represent heavy metals which can be released relatively well and more difficultly, respectively. Due to the implementation of isotopes which emit gamma rays, all measured values could be acquired without direct contact and without the need to take samples. The location of release was determined by means of NaI(Tl)‐scintillation detectors positioned alongside the outer walls of the grate. The time and the quantity of the release were measured with a detector located in a special absorption vessel for the purification of a partial flow of the exhaust gases.     

Low‐Carbon Magnesia‐Carbon Refractory: Use of N220 Nanocarbon Black

Addition of nanocarbon black up to 3 wt% was done in MgO‐C refractories, containing fixed 3 and 5 wt% of graphite, to study the effect on various refractory properties. Uniform distribution of carbon particles even at 1 wt% of nanocarbon black with 3 and 5 wt% of graphite was found to improve the refractory properties. The coked strength, hot strength, corrosion resistance, and oxidation resistance were found to be improved for nanocarbon‐containing MgO‐C refractory compared with the conventional refractory due to in situ formation of Al₄C₃. Higher amount of nanocarbon black was found to deteriorate the refractory properties.     

Effect of Drag‐Reducing Polymer on the Rate of Cementation of Copper Ion on Zinc Pellets

The effect of Polyox WSR‐301 drag‐reducing polymer on the rate of cementation of copper from copper sulfate solution over packed beds of zinc pellets was investigated. The mass transfer coefficient was found to increase with increasing superficial liquid velocity for solution free of polymer. The mass transfer data were correlated in the absence of drag‐reducing polymer, using the following equation J_d = 12.55 Re^–0.5 for the conditions 10 < Re < 1970 and 1265 < Sc < 1393. In the presence of polymer, starting from a Reynolds number (Re) 550, the rate of mass transfer was found to decrease by an amount ranging from 7.5 to 51 % depending on Re and polymer concentrations. The percentage decrease in the rate of mass transfer increased with increasing Re, passed through a maximum at Re = 1400 and then decreased rapidly with further increase in Re.     

Spectrophotometric Determination of Molybdenum‐Containing Compounds in Aqueous Glucose Solutions

The spectrophotometric determination of molybdenum‐containing compounds in aqueous glucose solutions using pyrazine‐2,3‐dicarboxylic acid was investigated. Determination of the molybdenum complex with pyrazine‐2,3‐dicarboxylic acid was performed at λ_max = 550 nm. The light absorption of the deeply violet complex follows Lambert‐Beer's law and can be measured with a molar absorptivity in the range of 4414–9020 L mol^?1cm^?1. The presented method is very sensitive and shows good reproducibility for the extinction values.     

Applying a Thermodynamic Model to the Non‐Stoichiometric Precipitation of Barium Sulfate

Thermodynamic models for aqueous Ba²⁺‐SO₄^2–‐Na⁺‐Cl^–‐solutions are compared in their accuracy to predict ion activities in saturated and supersaturated solutions. The Pitzer and the Bromley model are employed, taking into account ion pair formation of barium sulfate. Such models are then used to describe particle nucleation and growth, and finally they are imbedded in a mechanistic mixing‐precipitation model for a single feed semibatch process. The effect of the key operating parameters on the mean particle size is analyzed through simulations. The results are compared with previous experimental data, thus highlighting the significance of a proper choice of the thermodynamic model.     

Synthesis of a Fluorogenic Analogue of Sphingosine‐1‐Phosphate and Its Use to Determine Sphingosine‐1‐Phosphate Lyase Activity

Illuminating an ER enzyme : We report on the design and synthesis of a fluorogenic chemical sensor ( 1 ) to measure sphingosine‐1‐phosphate lyase activity in high‐throughput screening formats, as well as its validation using lyase knockout (Sgpl1?/?) cells.

     

过磷酸钙生产中磷矿的搭配

介绍磷矿的杂质对过磷酸钙生产的影响，并总结出不同磷矿的搭配方法。根据云浮市磷肥厂的生产实践，说明不同性质的磷矿搭配使用的可行性和重要性。     

Application of Aqueous Two‐Phase Systems for the Potential Extractive Fermentation of Cyanobacterial Products

The potential use of aqueous two‐phase systems (ATPS) to establish a viable protocol for the in situ recovery of cyanobacterial products was evaluated. The evaluation of system parameters such as poly (ethylene glycol) (PEG) molecular mass, concentration of PEG and salt was carried out to determine the conditions under which Synechocystis sp. PCC 6803 cell and cyanobacterial products, i.e., β‐carotene and lutein, become concentrated in opposite phases. PEG‐phosphate ATPS proved to be unsuitable for the recovery of cyanobacterial products due to the negative effect of the salt upon the cell growth. The use of ATPS PEG‐dextran (6.6 % w/w PEG 3350, 8.4 % w/w dextran 66900, TLL 17.3 % w/w, V_R 1.0, pH 7) and (4.22 % w/w PEG 8000, 9.77 % w/w dextran 66900, TLL 18 % w/w, V_R 1.0, pH 7) resulted in the growth of cyanobacteria (Synechocystis sp. PCC 6803) and the concentration of lutein in opposite phases. However, β‐carotene was seen to concentrate in the top phase together with the biomass. The results reported here demonstrate the potential application of ATPS to establish the conditions for an extractive fermentation prototype process for the recovery of cyanobacterial products.     

Identification of Low‐Molecular‐Weight Compounds Inhibiting Growth of Corynebacteria: Potential Lead Compounds for Antibiotics

The bacterial genus Corynebacteria contains several pathogenic species that cause diseases such as diphtheria in humans and “cheesy gland” in goats and sheep. Thus, identifying new therapeutic targets to treat Corynebacteria infections is both medically and economically important. CG2496, a functionally uncharacterized protein from Corynebacterium glutamicum, was evaluated using an NMR ligand‐affinity screen. A total of 11 compounds from a library of 460 biologically active compounds were shown to selectively bind CG2496 in a highly conserved region of the protein. The best binder was identified to be methiothepin (K_D=54±19 µM ), an FDA‐approved serotonin receptor antagonist. Methiothepin was also shown to inhibit the growth of C. glutamicum, but not bacteria that lack CG2496 homologs. Our results suggest that CG2496 is a novel therapeutic target and methiothepin is a potential lead compound or structural scaffold for developing new antibiotics specifically targeting Corynebacteria.