Industrial wastewater treatment for toxic heavy metals using natural materials as adsorbants

The presence of toxic heavy elements such as arsenic, cadmium and mercury in industrial wastewater and waterways is a serious pollution problem. The treatment of such contaminated water by conventional techniques, which often includes an ion-exchange or similar step, is expensive. This paper examines the use of natural materials such as hair, and certain plants, which are inexpensive, for the absorption and hence the clean up of heavy elements from polluted water. Our results show that these natural materials concentrate the heavy elements, in certain cases, to the extent of up to 500 fold or even better. The contact time required is of the order of several hours. The capacities of absorption vary from about 1 g/kg to about 5 g/kg for mercury, and are lower for arsenic and cadmium. The results show that with hair, nearly 10,000 liters of mercury contaminated water, a typical daily output from a 100 ton chlor-alkali plant, can be treated with about 1/2 kg of hair valued at about 25 cents. This makes the process extremely cost-effective compared to the conventional processes now in use.     

Trend in using TiO2 nanotubes as photoelectrodes in PEC processes for wastewater treatment

Photoelectrocatalytic (PEC) processes represent an effective way to exploit renewable energy in response to the sustainable development objectives. The synergy between photo and electrochemical processes inspired several papers and stimulated research toward new systems that could be increasingly adapted to work under visible or solar radiation, and with minimum bias potential. Since the first appearance of articles on PEC processes in the literature, titanium dioxide has been one of the most studied semiconductor materials: nanostructured electrodes have been especially considered such as nanotubes (NT), which are the main subject of the present article. The software VOSviewer is used to a preliminary analysis of metadata, related to the trend of the research on PEC processes; attention is then paid on the trend of NT-TiO₂ electrodes for application in wastewater treatment in the past year.     

Mass production of methane from food wastes with concomitant wastewater treatment

We developed a process for production of methane at a pilot scale. This process consists of three stages. The first stage is a semianaerobic hydrolysis/acidogenic step in which organic wastes are converted to various sugars, amino acids, and volatile fatty acids (VFAs). Operation temperature and pH were 45°C, and 5.0–5.5, respectively. Hydraulic retention time (HRT) was 2 d. To remove the putrid odor and to enhance the hydrolysis of organic wastes, a mixture of bacteria isolated from landfill soil was inoculated into the reactor. Total chemical oxygen demand (tCOD) and biological oxygen demand (BOD) were 36,000 mg/L and 40,000 mg/L, respectively. The second stage was an anaerobic acidogenic process, which can produce large amount of VFAs including acetate, propionate, butyrate, valerate, and caproate. Operation temperature and pH were 35°C, and 5.0–5.5, respectively. HRT was 2 d. The third stage was a strictly anaerobic methane fermentation step producing methane and carbon dioxide from VFAs. The working volume of upflow anaerobic sludge blanket (UASB) type reactor was 1200 L, and operation temperature and pH were 41°C, and 7.7–7.9, respectively. HRT was 12 d. Seventy two percent of methane at maximum was generated and the yield was 0.45–0.50 m³/kg VS of food wastes. Through the process, 88% of tCOD and 95% of BOD were removed. The wastewater was treated with the biological aerobic and anaerobic filters immobilized with heterotrophic and autotrophic nitrifying and denitrifying bacteria. Ninety percent of total nitrogen (T-N) was removed by this treatment. The residual T-N and total phosphorous (T-P) were removed by the algal periphyton treatment system. The final concentrations of nitrogen and phosphorous in the drain water were 53 and 7 mg/L, respectively.     

The thermodynamic method for selecting oxygen carriers used for chemical looping air separation

Chemical looping air separation (CLAS) has been suggested as a new and energy saving method for producing oxygen from air. The selection of suitable oxygen carriers is the key issue for CLAS system. This paper shows a comprehensive thermodynamic method for selecting oxygen carriers used for CLAS through studying the properties of 34 different oxygen releasing reactions referring to 18 elements at different temperatures. The research mainly includes analysis of oxygen releasing capacity by calculating the Gibbs free energy change (ΔG) and the equilibrium partial pressure of oxygen of the reduction or oxidation reaction at different temperatures. Oxygen content and transport capacity were calculated. The spontaneous reaction temperatures for oxygen releasing reactions were presented to determine the operating temperatures. Also, the minimum demand of the steam for the reduction reaction was discussed. On the basis of the comprehensive thermodynamic study, the oxide systems of CrO₂/Cr₂O₃, PbO₂/Pb₃O₄, PbO₂/PbO, Pb₃O₄/PbO, MnO₂/Mn₂O₃, and Ag₂O/Ag have been found suitable for the CLAS process in low temperatures (500–800 K). The systems of PdO₂/PdO, PdO₂/Pd, PdO/Pd, MnO₂/MnO, and MnO₂/Mn₃O₄ were suitable for medium temperatures (800–1100 K) CLAS process. And Co₃O₄/CoO, CuO/Cu₂O, Mn₂O₃/Mn₃O₄, and OsO₂/Os systems only worked successfully in high temperatures (1100–1400 K). In addition, the CaO₂/CaO system was not suitable for CLAS because of the reaction with steam. The various binders such as SiO₂, TiO₂, Al₂O₃, Y₂O₃, ZrO₂, and YSZ which have been used for CLC could also be the supports for CLAS oxygen carriers.     

Structured polyphenylenes as carriers of palladium nanoparticles used as selective hydrogenation catalysts

Structured polyphenylenes that are used as matrices for immobilization of palladium nanoparticles are synthesized through the cyclocondensation of acetylaromatic compounds followed by structuring at different temperatures and, as a result, different crosslink densities. The relationship between the structure and structuring temperature of the polymers is investigated. It is shown that the sizes of palladium nanoparticles immobilized in polyphenylene matrices depend on the conditions of polymer structuring. The resulting catalytic systems are examined for the selective hydrogenation of triple bonds in acetylene alcohols.     

碘量法测定氧载体中的活性氧

氧载体中活性氧气的含量是衡量氧载体实用性的一项重要指标。自行设计了一种改进的碘量法测定混合气体中氧气的装置,完成了混合气体中微量氧气的测定,将该方法用于固相合成氧合氧载体中活性氧的测定,取得很好的结果,为混合气体中氧气的测定提供了新思路。     

A review on industrial wastewater treatment via electrocoagulation processes

Every year, a large amount of wastewater is discharged from various industries into the environment, and various methods are used to treat wastewater to reduce the amount of pollutants. Electrocoagulation (EC) is an electrochemically based technique that generates coagulant species in situ from the electrodissolution of sacrificial anodes, usually made of iron or aluminum destabilizes suspended, dissolved, or emulsified pollutants by using an electric current. It has a potential in removing various kinds of pollutants including organic and inorganic contaminants for various types of wastewater. The effectiveness of EC process depends on various parameters including pH, electrode, operation time, and current density. The goal of this study is to review the most relevant literatures that were published recently. The main challenges associated with the EC process are electrode passivation and energy consumption. EC compared with other common methods has advantages such as reducing energy consumption and reducing operating costs.     

An ab initio theoretical research on perfluorochemicals as oxygen carriers

In order to elucidate the nature of the interaction force effected in perfluorochemical artificial blood, the basis set dependence of the stabilization energy between a model perfluorochemical and oxygen was investigated in detail. The basis set superposition error was removed in each case. The interaction was estimated to arise from dispersion forces.     

Recent advances in persulfate-based advanced oxidation processes for organic wastewater treatment

In recent years, with the emergence of new pollutants, the effective treatment of wastewater has become very important. Persulfate-based advanced oxidation processes have been successfully applied to the treatment of wastewater, such as wastewater containing antibiotics, pharmaceuticals and personal care products, dyes, endocrine-disrupting chemicals, chlorinated organic pollutants, and phenolics, for the degradation of refractory organic contaminants. This paper summarizes the production of sul...     

A diruthenium-substituted polyoxometalate as an electrocatalyst for oxygen generation

Transition metal heteropolyanions have been used to catalyze a variety of organic oxidations but have not previously been used for O2 generation, despite sharing some structural similarities with dioxoruthenium water-oxidation catalysts. In this study, we report that the di-Ru-substituted polyoxometalate (POM) [Ru2Zn2(H2O)2(ZnW9O34)2]14- can be used to catalyze the electrochemical generation of O2. By comparing the behavior of this compound to that observed using a mono-Ru-substituted POM catalyst, we show that adjacent Ru sites are necessary to observe O2 generation. These observations suggest a reaction pathway involving two Ru-bound oxygen species combining to form O2 and are consistent with the accepted mechanism of electrochemical oxygen evolution. Finally, analysis of the observed electrode kinetics yields a Tafel slope of roughly 120 mV, which is similar to values reported previously for perovskite anodes.     

Lecithin organogels used as bioactive compounds carriers. A microdomain properties investigation

Organogels were obtained by adding small amounts of water to a solution of lecithin in organic solvents. Either isooctane or isopropyl palmitate and isopropyl myristate were used as the continuous organic phase of the gels. EPR spectroscopy using both DSA membrane-sensitive and lipophilic spin probes was applied to define the dynamic structure of the surfactant monolayer and the continuous oil phase of lecithin organogels. It was found that by increasing the water quantity, an increase of the polar head area per lecithin molecule was induced, and as a consequence the total interface expanded. It was found that the use of esters as organic solvents induced a decrease of the size of the dispersed structures. The interconnection of the aqueous microdomains and their dynamics were monitored by both static and time-resolved fluorescence quenching spectroscopy using Ru(bipy)32+ as fluorophore and Fe(CN)63- as quencher. It was found that the rates of inter- and/or intra-micellar exchange of water molecules were very slow because they appeared quite immobilized close to the lecithin polar heads. According to the results of the dynamic studies, appropriate organogels were formulated and used to incorporate model bioactive compounds with medicinal or cosmetic interest such as caffeine and theophylline. When these systems were tested for trans-membrane diffusion, they showed a 24 h permeation of 20% and 35%, respectively.     

Emulsion approach to production of polymer films used as carriers of lysozyme

A new approach to producing polymer films with an immobilized bactericidal enzyme, lysozyme, is proposed based on oil-in-water emulsions containing nonionic surfactants and hydrophobic and hydrophilic polymers. The rheological properties, stability, dispersity, and film-forming ability of the emulsions are studied. It is established that lysozyme is present in the films in a nanocrystalline form, which ensures its rapid release into aqueous buffer solutions with retaining its enzymatic activity.     

Fluorinated derivatives of a polyaspartamide bearing polyethylene glycol chains as oxygen carriers

In this paper the synthesis and characterization of new fluorinated polymers based on a polyaspartamide bearing polyethylene glycol (PEG) chains, are reported. The starting material was the α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA), a water soluble and biocompatible polymer, that has been derivatized with both polyethylene glycol (with a molecular weight of 2000 Da) and 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole. By varying the amount of the fluorinated oxadiazole, three samples have been prepared and characterized by FT-IR, ¹H NMR, ¹⁹F NMR and UV-VIS spectroscopy. Size exclusion chromatography analysis of these copolymers revealed the occurrence of a self-association process in aqueous medium. The value of critical aggregation concentration has been evaluated by performing a tensiometric study, whereas the size of these aggregates has been determined by photon correlation spectroscopy. Oxygen solubility studies in aqueous solutions of these fluoropolymers showed their ability to maintain high oxygen levels in solution. The biocompatibility of these fluoropolymers has been evaluated by performing an in vitro viability assay on human chronic myelogenous leukaemia cells (K-562), chosen as a model cell line, and haemolysis experiments on human red blood cells. All these properties suggest the potential use of these fluoropolymers as artificial oxygen carriers.     

Controlled backwashing in a membrane sequencing batch reactor used for toxic wastewater treatment

A new control algorithm for performing filtration in a membrane sequencing batch reactor (MSBR) to prevent fouling is presented. Based on continuous measurements of the transmembrane pressure (TMP) and the permeate flux, the algorithm decides when to initiate backwashing. The algorithm was tested on a laboratory scale bioreactor treating synthetic wastewater containing 4-chlorophenol (4CP) as model toxic compound and filtration was carried out using a submerged tubular membrane module and a diaphragm pump. Several controller configurations were tested for different MSBR cycles. The results showed that the proposed algorithm was robust against the highly varying mixed liquor characteristics and was able to keep the TMP below critical values and maintain the flux at a maximum for most of the filtration time. Therefore, despite possible frequent backwashes, the total filtration time was minimized.     

Polylysine-modified polyethylenimines as siRNA carriers for effective tumor treatment

Polyethylenimine-poly(L-lysine)(PEI-PLL) copolymer was synthesized via ring-opening polymerization of L-lysine N-carboxyanhydride(Lys(Z)-NCA) initiated by PEI. The complexation of PEI-PLL with si RNA was studied by particle size and zeta potential measurements. The flow cytometric analysis and confocal imaging showed its excellent intracellular trafficking ability. PEI-PLL displayed higher gene silencing efficiency and lower cytotoxicity than commercial PEI-25 k in vitro. In the antitumor study, PEI-PLL was further combined with si VEGF and showed obviously tumor inhibition effect for the treatment of CT26 tumor model. Therefore, PEI-PLL is a promising si RNA carrier candidate for further antitumor treatment in vivo.     

Cationic polyhedral oligomeric silsesquioxane (POSS) units as carriers for drug delivery processes

Quaternary ammonium functionalized polyhedral oligomeric silsesquioxane (OctaAmmonium-POSS) units, widely employed as additives in ceramic and polymeric systems, possess many attributes which make them attractive as biocompatible drug carriers: nanoscale size, three-dimensional functionality, efficient cellular uptake, low toxicity, and high solubility.     

Hydroxo-bridged dinuclear cobalt(II) complexes of OBISDIEN and OBISTREN as oxygen carriers

Abstract

The hydroxo-bridged dinuclear cobalt(II) complexes of the macro-cyclic and macrobicyclic dinucleating ligands OBISDIEN and OBISTREN form thermodynamically stable dioxygen adducts. Although the values of the oxygenation constants of cobalt complexes usually increase with an increase in the number of basic amino groups coordinated to the cobalt centers, these complexes are unusual in that the oxygenation constants of the complex formed from OBISDIEN is about three orders of magnitude higher than the analogous complex formed from OBISTREN. The difference in behavior must be due to differences in steric strain. Since crystal structures are not available, steric effects were estimated by the use of molecular mechanics. By application of the molecular modelling program SYBYL it was determined that the distortions of the cryptand ligand necessary to form the hydroxo-bridged dioxygen complex are much greater and more energetic than those of the macrocyclic ligand. Both ligands were found to form excellent oxygen carriers because of facile oxygenation-deoxygenation reactions of their dinuclear cobalt complexes, and because of almost immeasurably slow metal-centered degradation. Moreover, the ligands were not changed during degradation, so that the oxygen-carrying complexes could be easily regenerated by electrolytic reduction.     

Synthetic and natural polymers as drug carriers for tuberculosis treatment

Drug forms based polymer carriers of prolong action were created for toxicologic effect of drug to be reduced in spite of long treatment of diseases. In present work a number of synthesis and natural polymers have been studied as carriers of antituberculous drugs for controlled delivery application. Following as drugs as isoniazid and ethionamide were incorporated into polymeric matrix (segmented polyurethanes, polyvinyl alcohol) and chemically bound with the polymer chain by covalent or electrostatic forces (aldehyde- and carboxymethylderivatives of polysaccharides). Biodegradation of polymeric systems and the release of drugs were studied by various physico-chemical methods. It was shown that the drug release depends of method of the immobilization, type of the drug/polymer bonding, drug loading. The bacteriostatic activity of obtained systems was determined. The possibility of tuberculosis treatment was proved in experiments of animals.     

Microcalorimetric qualitative analysis of biofilm development in porous media used in wastewater treatment by constructed wetland

In wastewater treatment by constructed wetland, the biodegradation capability of the biomass developed in the soil is one of the most important factors. For this kind of treatment unit, soil properties are studied to improve its filtration capacity and hydraulic residence time of the wastewater. The impact of soil properties like porosity and soil components on biomass development and biodegradation capacity seem to be less studied certainly due to the complexity of microbial identification techniques currently used. The study presented here is a preliminary work to validate that calorimetric technique could be a tool in the understanding of biodegradation capacity of wastewater treatment processes. Biofilm is preliminary developed in columns filled with different porous materials of well known porosity and constitutive components. These columns are fed with the same continuous flow of synthetic solution (C, N, and P) as a substrate amending during 3 weeks. Then each week, 2 mL samples of porous media from these columns are analyzed in isothermal calorimeter for 48 h. Net heat flow is recorded before and after substrate injection. This work results in the definition of the procedure for batch experiments in calorimeter for wastewater process efficiency. The results of these experiments show that the microbial reaction due to substrate amendment is highly depending on the porous material used for biofilm growth. Indeed calorimetric signals recorded lead to conclude that biofilm grown on plastic beads has a faster and more intensive reaction to glucose amendment than biofilm grown on glass beads. At least, two glass beads samples analyzed in the calorimeter after the same duration of feeding with synthetic solution have very different response to glucose or synthetic solution.