利用天然浓缩丹宁合成新型凝胶吸附剂通过表面沉淀去除水溶液中铅

Lead has caused serious environmental pollution due to its toxicity, accumulation in food chains and persistence in nature. In this paper, removal of lead from aqueous solutions is investigated using a novel gel adsorbent synthesized from natural condensed tannin. The novel adsorbent performs in aqueous solutions as a weak base with valid basic groups of 1.2mmol·g-1 tannin gel particles and therefore results in the elevation of pH value of aqueous solutions. Even when initial pH is 3.6, final pH at equilibrium can climb up to 6.5 that is above the pH value for Pb(OH)2 precipitation formation and then lead can be removed from wastewater by this so-called surface precipitation. The adsorption isotherm can be expressed by the Langmuir equation and the maximum capacity for adsorption of Pb is up to 92 mg·g-1 (based on dry adsorbent) when initial pH value is 3.6. Hence, the adsorbent does offer favorable properties in lead removal with respect to its high adsorption capacity at low initial pH value, which     

The use of natural (Pinus pinaster) resin in the production of printing ink and the printability effect

Alkyd resins are generally used in the production of printing inks. All industries look for alternative raw materials in the production of ink with the growing inclination toward using natural products. Resins forming the vehicle of the ink to be obtained from natural resources will provide benefits for the environment, nature, and living creatures. The aim of the study was to promote the use of natural resin in the ink system. Natural Pinus pinaster resin was added into vegetable and mineral oil-based solvents in pure form with alkyd resin in different amounts and ink varnishes of different combinations were prepared. Then, printing inks were produced from these varnishes in pure and hybrid form. Following the assessment of the rheological properties of the inks prepared, printing tests were conducted to assess the printing quality parameters. Ideal mixing ratios of the natural resins in the ink were determined for printability. The environmental importance and advantages of the use of natural resins were discussed. Recommendations were given in line with the results to encourage widespread use of natural resins in near future.     

Effect of Electrolyte and Temperature on Volatile Organic Compounds Removal from Wastewater Using Aqueous Surfactant Two-Phase System of Cationic and Anionic Surfactant Mixtures

Abstract

Benzene, toluene, ethylbenzene, and xylene are frequently observed contaminants in industrial wastewaters causing concerns about environmental and health effects. An aqueous surfactant two-phase (ASTP) extraction system using mixtures of cationic and anionic surfactants have been shown to be a promising surfactant-based separation technique to concentrate solutes such as proteins and dyes from aqueous solution. A phase separation of a surfactant solution occurs at certain surfactant compositions and concentrations, forming two isotropic phases. One is rich in surfactant aggregates (surfactant-rich phase) and the other is lean in surfactant aggregates (surfactant-dilute phase). Most of the organic contaminants tend to solubilize and concentrate in the surfactant-rich phase, leaving the surfactant-dilute phase containing only small amounts of contaminants as remediated water. The effect of NaCl addition on the critical micelle concentration (CMC) and the extraction ability of ASTP formed by mixtures of cationic surfactant (dodecyltrimethylammonium bromide; DTAB) and anionic surfactant (alkyl diphenyloxide disulfonate; DPDS) at 50 mM total surfactant concentration with a 2:1 molar ratio of DTAB:DPDS was investigated; the CMC of the mixture slightly decreases with increasing NaCl concentration. The extraction and preconcentration of benzene are greatly enhanced by added NaCl. The higher the degree of hydrophobicity of contaminants, the greater the extraction into the surfactant-rich phases. At 1.0 M NaCl addition, about 95% of xylene, 92% of ethylbenzene, 90% of toluene, and 79% of benzene are extracted into the surfactant-rich phase within a single stage extraction and the contaminant partition ratios can be as high as 395 for xylene, 273 for ethylbenzene, 206 for toluene, and 84 for benzene, which are greater than those obtained from the conventional ASTP extraction system using nonionic surfactants.     

Anionic Surfactant Impregnation in Solid Waste for Cu2+ Adsorption: Study of Kinetics,Equilibrium Isotherms,and Thermodynamic Parameters

Coconut shell powder (CP) and diatomite (Di) were modified with microemulsion (μE), producing low-cost adsorbents for copper (II) removal from aqueous solutions. The μE was prepared using as active phase an anionic surfactant sodium octanoate (SO), obtained from the saponification of octanoic acid. The effect of modification on the adsorption capacity of Cu⁺² was evaluated taking into consideration the solution pH, equilibrium time, temperature, and initial concentration of metal in solution. The adsorbents were analyzed by characterization techniques of X-Ray Fluorescence, scanning electron microscope and Fourier Transform Infrared Spectroscopy. The obtained experimental data were analyzed using the equations of Langmuir, Freundlich, Temkin, and Dubinin Radushkevich models. The initial concentration of 50 mg Cu⁺²/L solution and 0.2 g of adsorbent materials modified with the μE presented a Cu⁺² removal efficiency of 86.81% and 96.3% for CP and Di, respectively. The kinetic models of pseudo first-order, pseudo second-order, Elovich, and intraparticle diffusion were used in this study to describe the adsorption rate. The presence of sodium octanoate functional (OS) group provided ion exchange sites suitable to Cu⁺² adsorption. The stability of the OS impregnation using microemulsion was evaluated based on a desorption study.     

Quaternary Amine Modified Persimmon Tannin Gel: An Efficient Adsorbent for the Recovery of Precious Metals from Hydrochloric Acid Media

Persimmon tannin was chemically modified to prepare a quaternary amine type of adsorption gel, named as quaternary amine modified persimmon tannin (QAPT) gel. The QAPT gel has been used to investigate the adsorption behaviors for Au(III), Pd(II), and Pt(IV) from HCl media. It was found that the gel exhibited good selectivity towards precious metals over a wide concentration range of HCl. However, it exhibited poor affinity towards base metals such as Cu(II), Fe(III), Ni(II), and Zn(II). The adsorption isotherms of the gel for precious metal ions were described by the Langmuir model. The maximum adsorption capacities for Au(III), Pd(II), and Pt(IV) were evaluated as 4.16, 0.84, and 0.52 mmol g^?1, respectively. Although the anion exchange is the main mechanism for the adsorption of anionic species of Au(III), Pt(IV), and Pd(II), adsorption of Au(III) is followed by subsequent reduction, which results in the extraordinary high adsorption capacity for Au(III). Adsorption behavior of QATP gel for Au(III) was also compared to that of the persimmon tannin, the feed material.     

Implementation of Hybrid Inorganic/Organic Adsorbents for Removal and Preconcentration of Heavy Metals from Industrial Waste and Drinking Waters

Three hybrid inorganic/organic adsorbents based on alumina and phenylazoformic acid 2-phenylhydrazide were synthesized, characterized and examined for their heavy metal sorption properties. The main purpose of this research paper is to study and explore the combined hybrid characters of inorganic/organic sorbents for the selective removal and preconcentration of heavy metals via static and dynamic solid phase techniques from industrial wastewater and drinking tap water samples as well. The hybrid inorganic/organic adsorbents were identified as strongly resistive to leaching in solutions with pH 1–7 and thermally stable up to 350°C. Optimization of heavy metal removal by implementation of newly designed hybrid inorganic/organic adsorbents was studied in presence of various factors as the effect of pH of contact solution and reaction time via determination of the metal sorption capacity and distribution coefficient. The hybrid adsorbents were successfully implemented for the selective removal of Pb(II), Cu(II), Fe(III), and Cr(III) from industrial wastewater samples with recovery values in the range of 91–99 ± 2–3% as well as 98–99 ± 1–3% for the selective preconcentration of Pb(II), Cu(II), and Cr(III) from drinking tap water samples without noticeable interference caused by the matrix effect.     

Amidoximated Sunflower Stalks (ASFS) as a New Adsorbent for Removal of Cu (II) from Aqueous Solution

A sunflower stalk graft copolymer was prepared by the reaction of ground sunflower stalks (SFS) with acrylonitrile (AN) in aqueous solution initiated by KMnO₄-citric acid (CA) system. It has been shown that the grafting parameters, such as concentration of KMnO₄, AN, and CA, have a significant effect on graft copolymerization. The temperature as well as the duration time of the reaction were studied and also showed a significant effect on the graft copolymerization reaction. The possible reaction was deduced by estimation of nitrogen content. Amidoximation of the grafted stalks was performed by the reaction of grafted SFS with hydroxylamine hydrochloride in alkaline medium to obtain amidoximated sunflower stalks (ASFS). The obtained amidoximated product was detected by FT-IR spectra. The effects of pH and concentration of the adsorbent, ASFS, on adsorption of Cu (II) were studied. The study shows that the ASFS was effectively used in adsorption of Cu (II) ions from aqueous solution. The adsorption data obeyed Langmuir and Freundlich isotherms.     

Cationic Gemini Surfactant as a Corrosion Inhibitor and a Biocide for High Salinity Sulfidogenic Bacteria Originating from an Oil-Field Water Tank

A novel cationic gemini surfactant (NCGS) was synthesized and characterized. The inhibitory effect of NCGS was evaluated on the basis of protecting a metal surface from the salinity (5.49 % NaCl) and the activity of environmental sulfidogenic bacteria which originated from an oil-field water tank. Sulfidogenic bacterial activities were determined based on sulfide production, redox potential, changes in biofilm structures and constituents and metal corrosion rate calculations. At high surfactant concentrations, the sulfide production was completely inhibited as well as a considerable drop in the redox potential was observed in the reactor’s bulk phase. A minimum inhibitory concentration of the NCGS was achieved at a concentration of 1 mM. The NCGS showed a high ability to inhibit a biofilm over the metal surface at a concentration of 0.1 mM. The lowest metal corrosion rate was detected at a concentration of 5 mM with a metal corrosion inhibition efficiency of 97 %. In addition the NCGS showed a nonspecific biocidal activity against Gram-positive and Gram-negative bacterial strains.     

Layered Double Hydroxides Derived from MIL-88A(Fe) as an Efficient Adsorbent for Enhanced Removal of Lead (II) from Water

The efficient removal of lead (II) from aqueous solution remains a big problem and the development of novel nanomaterials as adsorbents by various technologies to solve this problem is promising. This study contributed a novel nanostructure of MIL-88A-layered double hydroxides (LDHs) as the adsorbent for Pb²⁺, which was synthesized by a two-step solvothermal method with MIL-88A(Fe) as the precursor. The as-prepared material featured a chestnut-like core-shell structure, and exhibited excellent removal performance towards Pb²⁺ from water in comparison to MIL-88A(Fe) and LDHs (directly synthesized). The adsorption of Pb²⁺ by the MIL-88A-LDHs conformed to the pseudo-second-order kinetic model and the Langmuir and Freundlich isotherm models. The maximal adsorption capacity was 526.32, 625.00, and 909.09 mg g⁻¹ at 278, 298, and 318 K, respectively. The thermodynamic parameters suggested that the adsorption was an endothermic, entropy-increasing, and spontaneous reaction. X-ray photoelectron spectroscopy (XPS) analysis indicated that the surface complexation was mostly responsible for Pb²⁺ elimination. The MIL-88A-LDHs can be readily regenerated and showed good cyclic performance towards Pb²⁺. Thus, the as-prepared MIL-88A-LDHs may hold promise for the elimination of aqueous heavy metals.     

Membrane Characteristics and Fouling Study in MEUF for the Removal of Chromate Anions from Aqueous Streams

Abstract

Micellar‐Enhanced Ultrafiltration (MEUF) of the chromate anions from aqueous solutions has been studied at room temperature (28±2°C) using cationic surfactants, cetyltrimethylammonium bromide (CTAB), and cetylpyridinium chloride (CPC), micelles of which adsorb the chromate ions by electrostatic interactions. The solution is processed by ultrafiltration, using a membrane with a pore size small enough to block the passage of the micelles and the adsorbed ions. The process is highly efficient in removing the chromate ions. In the absence of other electrolytes, chromate ion rejections up to 99% were observed at optimal conditions of pH, pressure, temperature, feed chromate, and surfactant concentrations. The presence of added NaCl reduces the chromate rejection, but it was still considerable (up to 82%), even in the presence of 100 mM NaCl. The rejection rate of chromate was found to be highly dependent on the pH of the feed solution. The influence of membrane characteristics on the chromate ion removal was also studied. Various resistances like fouling resistance, concentration polarization resistance, and membrane resistance were also estimated to quantify their effects on the removal efficiency and on the flux behavior.