Removal of Poly Aromatic Hydrocarbons (PAHs) from Water: Effect of Nano and Modified Nano-clays as a Flocculation Aid and Adsorbent in Coagulation-flocculation Process

Water treatment process involving simultaneous action of adsorption on different nano and organo-modified nano-clays followed by coagulation-flocculation by alum and poly aluminium chloride (PAC) has been evaluated for the removal of PAHs (naphthalene, acenaphthalene, phenanthrene, fluoranthene, anthracene, and pyrene) from water. When clay minerals along with alum and PAC were used for treatment, 37.4–100.0% removal of PAHs was observed compared to 20–38% removal using normal water treatment process with either alum or alum + PAC. The effectiveness of clay minerals for removal of PAHs followed the order (P < 0.05): halloysitenano-clay (HN-clay) < normal bentonite (NB-clay) < hydrophilic nano-bentonite (HNB-clay) < nano-montmorillonite modified with dimethyl dialkyl amine (DMDA-M-clay) ≈ nano-montmorillonite modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M-clay) ≈ nano-montmorillonite modified with octadecylamine (ODA-M-clay) in combination with alum + PAC. The modified treatment process (alum + PAC + clay minerals), where water was initially treated with clays followed by normal process of coagulation (alum + PAC), was found to be the most effective method with maximum removal for ODAAPS-M-clay (97.7–100.0%) which is at par wih ODA-M (97.0–100.0%), and DMDA-M-clay (94.8–100%). The removal of PAHs varied in the order: naphthalene ≈ acenaphthalene > anthracene ≈ pyrene > phenanthrene > fluoranthrene. The treatment combination having the maximum removal capacity was also used eficiently for the removal of PAHs from natural and fortified natural water. This article demonstrated adsorption-coagulation integrated system has the potential to remediate PAHs polluted water.     

Poly(methyl methacrylate) as incorporation medium for spent ion-exchange resin. II. Simulated resin

The incorporation and final containment of spent ion-exchange resins into poly(methyl methacrylate) (PMMA) was investigated in the present study. Test blocks of PMMA with 50% incorporated inactive resin were subjected to radiation doses of 10⁵–10⁷ rad at a dose rate of 50 rad/s. The high radiation doses impaired the mechanical properties of the final products. Both compressive strength and hardness decreased with increasing the particle size of the ion-exchange resin. DTA diagrams showed the thermal instability of the final solidification product at about 400°C. Leaching experiments on incorporated blocks of active resins labelled with Cs-137 and Ce-144 showed that cesium activity was more easily released in leachant solutions than was cerium activity. Cumulative leaching rates for both Cs and Ce were lower in deionized water than in undergroud water. The mechanical, thermal, and leaching data obtained illustrate the suitability of PMMA for immobilization of spent ion-exchange resins with low specific activity.     

The effect of temperature on the stability of ion-exchange resins in aqueous medium

The effect on ion-exchange resins of the polystyrene type of a thermal treatment has been studied by heating strong cation and strong anion resins in water at 95°C and 250°C and obtaining the IR spectra of the remaining resins as well as those of the decomposition products extracted by the water. The degradation of the resins is highly dependent on their ionic form. The ? (OH^?) and the ? (H⁺) forms are more labile, losing completely their exchange capacity at 250°C, while the ? (Li⁺) form retains considerable ion-exchange capacity. On the other hand, the hydrothermal process affects differently the backbone of the anion and the cation resins. There are similarities in the type of decomposition products found after hydrothermal treatment with those observed after radiolytic exposure of the resins. Heating the resins in water reduces the crosslinking of the polystyrene matrix.     

The Separation of Zn and Cu Using Chelating Ion Exchangers and Temperature Variations

Abstract

This paper reports the results of a study on the ion-exchange equilibrium of Cu ²⁺ and Zn ²⁺ at different temperatures on chelating ion-exchange resins: Amberlite IRC-718 (iminodiacetic acid based functional groups), VPC-1 (picolinic acid based) and thiourea-based resins. The separation factors and the conditional equilibrium constants of the ion-exchange reaction were determined in temperature range from 15 to 75 °C. An estimation of thermodynamic functions has also been carried out. Possibility of the separation of Cu and Zn mixture by dual temperature ion-exchange method has been demonstrated.     

The effect of corrosion particles present in water solutions on the behavior of strong acid cation-exchange resins during the process of cobalt removal

The effect of the presence of corrosion particles on the behavior of different structure types of cation-exchange resins during the adsorption process of ⁶⁰Co from water solutions was studied. Comparative valuation of sorption behavior and capacity of polyreticular and monoreticular structure type cation-exchangers was carried out. It was found that the ion-exchange filtration efficieny depends upon the presence of corrosion particles on the surface of ion-exchange beads and in their pore structure. The cation-exchange process of ⁶⁰Co is affected differently by different structure type ion-exchange resins. The fouling phenomenon caused by iron-corrosion particles during the water clean-up process at a RWCU system in BWR and by CVSE demineralizers in PWR dose not affect negative phenomenon for ion-exchange behavior of ion-exchange resins to remove polyvalent ions from the water. The polyreticular cation exchanger Amberlite 200C can better remove ⁶⁰Co cations from water solutions than the monoreticular (gel type) cation-exchanger Amberlite IR 120. Evidently this is due to the true porous macroreticular structure of the cation-exchange beads. In parallel with the ion-exchange processes, the sorption process of the corrosion products situated on the larger surface area of the true physical pore structure of Amberlite 200C also plays an important role. The information obtained will be very useful to the technological service of nuclear power stations.     

The synthesis of spherical activated carbons containing zinc and their photochemical activity

Spherical activated carbon (AC) containing photocatalyst was prepared using strong and weak acid ion-exchange resins as starting materials. These resins were treated with an aqueous solution of Zn²⁺ or [Zn(NH₃)₄]²⁺ and both treated resins and non-treated resins were carbonized and activated. The physicochemical characteristics of the AC samples were examined using XRD, SEM, EDS, BET, EPMA, ESR, compressive strength and zinc content. The photocatalytic activity was evaluated by measuring the humic acid (HA) removal efficiency using UV/photocatalyst system. When strong acid ion-exchange resins (SZ samples) were used to prepare AC containing zinc, the zinc was found to have ZnS crystal structures, whereas in case of the use of weak acid ion-exchange resins (WZ samples), the zinc was found to have ZnO crystal structure. Both the SZ and WZ samples had spherical shape except the WZ-A-900 and had a good BET specific surface area. In the HA removal test using a floating UV/photocatalyst system, the WZ samples showed higher HA removal efficiency than the SZ samples.     

Modified Shrinking Core Model for Reversible Sorption on Ion-Exchange Resins

Abstract

A modified shrinking core model is proposed to correlate dynamics of acid sorption on weak base ion-exchange resins in free base form. The model considers reversibility of the sorption process which is ignored in the conventional shrinking core model. The model is easy to apply and is shown to yield results which are in agreement with a computationally intensive rigorous model. The model is successfully verified using the experimental data on sorption of strong acids (HCl and HNO₃) on weak base resins (Dowex WGR-2 and Amberlite IRA-93).     

Integration of immersed membrane ultrafiltration with the reuse of PAC and alum sludge (RPAS) process for drinking water treatment

Effects of PAC and alum sludge generated from water treatment process on the effluent quality and fouling of immersed UF membrane were systematically investigated with representative source of natural water and the efficiency of coagulation, PAC adsorption and RPAS to treat natural surface water prior to UF were compared. It was found that the average turbidity removal by RPAS could reach up to 80.2%, and the turbidity removal of immersed membrane UF was independent of the influent, which could be kept at 99%. Particulates were reduced after being pre-treated by different processes, and particles with sizes ranging from 0.5 to 3.5 μm and larger than 13.5 μm were effectively removed by RPAS. UF coupled with RPAS pre-treatment got the best removal for DOM compared to other processes with average DOC and UV₂₅₄ removal 54.1% and 47.2% due to the high removal in the influent of UF. The residual alum content in the effluent of RPAS with UF was less than coagulation and bacteria were almost all removed by membrane. The membrane-fouling was mitigated by pre-treatment processes at different degrees, TMP of UF coupled with RPAS process was relatively stable in 15 d of run, the adsorption of PAC and large number of Al(OH)₃ complexes and precipitates for the foulant molecules might be an important mechanism.     

Application of a three-dimensional ion-exchange electrolyte in the deoxygenation of low-conductivity water

A solid ion-exchange electrolyte has successfully been used in the electrochemical deoxygenation of low-conductivity water. A packed bed three-dimensional cathode was mixed with ion-exchange resin. Oxygen-rich low-conductivity water was passed through the three-dimensional cathode and the dissolved oxygen was reduced to water. A sufficient ionic conductivity in the three-dimensional electrode was obtained for both distilled water and tap water by small-size strong cation exchange resins in the H+ and Ca2+ forms, respectively. Deoxygenation efficiencies of over 99.9% were achieved.     

Synthesis,Characterization, and Evaluation of Gel‐Type Poly(4‐Vinylpyridine) Resins for Plutonium Sorption

Abstract

Three different cross‐linked (4, 8, and 12%) gel‐type strong‐base poly(4‐vinylpyridine) resins (PVP) have been synthesized and characterized by elemental analysis, IR, exchange capacity, and moisture content. The uptake of plutonium and uranium was measured as a function of nitric acid concentration using all the three PVP resins. Plutonium sorption and elution kinetics experiments were also performed on all three PVP resins and compared with the benchmark, a gel‐type quarternary ammonium type anion‐exchange resin. The plutonium sorption rate decreases with the increase in cross‐linkage of the resin. All the three PVP resins exhibit better elution kinetics compared to the benchmark. The results on kinetic experiments performed on all three‐gel‐type resins indicated 8% gel‐type PVP resin with 50–100 mesh as a better candidate for plutonium processing or purification. Radiation degradation studies were carried out on the 8% PVP resin by gamma irradiation up to 200 MRad. The irradiated resins were characterized by IR, TGA, and SEM.

The exchange capacity, moisture content, and plutonium uptake were also evaluated for the irradiated PVP resins in comparison with the benchmark. The results indicated a better radiation stability for PVP resin over the benchmark.     

Enhancement of Coagulation Flocculation Process Using Anionic Polymer for the Post Treatment of UASB Reactor Effluent

This study was conducted for the treatment of up-flow anaerobic sludge blanket (UASB) reactor effluent by polymer assisted coagulation–flocculation process. The efficiency of alum, FeCl₃, and polyaluminum chloride (PAC) was observed alone and in coupled with anionic polymer (Synpol). The results revealed that FeCl₃ and PAC are efficient to remove 99% of turbidity, 83% of total suspended solids (TSS), 82% and 85% of biochemical oxygen demand (BOD) and chemical oxygen demand (COD), respectively, and 99.5% removal of total coliforms (TC) and fecal coliforms (FC). The addition of anionic polymer to alum, FeCl₃, and PAC reduces the sludge volume upto 25%.     

Studies on Cesium Uptake by Phenolic Resins

Abstract

The selective removal of cesium by phenolic ion-exchange resins from highly salted alkaline radioactive solutions was studied. The resins were synthesized by alkaline polycondensation of phenol, resorcinol, catechol, and a resorcinol-catechol mixture with formaldehyde and characterized for their moisture regain, ion-exchange (H⁺→Na⁺) capacity, and distribution coefficient (K_D ) for cesium. The effects of open and sealed curing of the polymers on their properties were studied. The effect of Na⁺, NaOH, and Cs⁺ concentration on the uptake of cesium by resorcinol-formaldehyde resin was investigated, in particular. The chemical, thermal, and radiation stabilities of the polymers were also studied.     

Hybrid resins from polyisocyanate,vinyl ester,melamine formaldehyde and water glass: structure and properties

Abstract

Hybrid thermosets were produced from polymeric methylene diphenyl isocyanate (PMDI), styrene cross-linkable vinyl ester (VE) and water glass (WG) using melamine formaldehyde (MF) resin as additional reactive emulsifier. Vinyl ester (VE) was added to the PMDI/MF mixture in which the WG was dispersed next. The content of MF in the resin formulation was varied between 0·5 and 15 wt-%. The resulting water in oil type (W/O) emulsion (water=WG, oil=organic phase composed of PMDI+VE+MF) was cured at room temperature for 24 h followed by post-curing at T=100°C for 4 h. The chemorheology of the hybrid resins was assessed by plate/plate rheometry. Information on the morphology of the cured hybrid resins was received from scanning electron microscope (SEM), atomic force microscopic (AFM) and dynamic mechanical thermal analysis (DMTA) studies. The mechanical and fracture mechanical properties as well as the resistance to thermal degradation of the hybrid thermosets were determined and discussed.     

Technetium-99 Removal from Process Solutions and Contaminated Groundwater

Abstract

The predominant form of technetium under oxic conditions is the pertechnetate anion (TcO₄ ^?), which is highly soluble in water and readily mobile in the environment. Technetium-99 is of particular concern because of its persistence and mobility.

Various equipment decontamination and uranium recovery operations at the Portsmouth Gaseous Diffusion Plant generate a “raffinate” waste stream characterized by toxic heavy metals, high concentration of nitric acid, and low levels of radionuclides (²³⁵u and ⁹⁹Tc). Dilution and adjustment of solution pH to a value of 8.2 to 8.5 precipitates a heavy-metals-sludge and a filtrate. The removal of ⁹⁹Tc from these waste streams and from contaminated groundwater can be accomplished using anionic ion-exchange resins.

Batch equilibrium and packed column breakthrough and regeneration studies were performed using inorganic sorbenta and organic ion-exchange resins (Dowex SRB-OH and Reillex resins). These studies were performed on actual and surrogate raw raffinates, filtrates, and surrogate groundwater samples. The experimental conditions were chosen to closely represent the actual process.     

Removal of Aluminum(III)-Based Turbidity in Water Using Hydrous Titanium Oxide Dispersed in Ion-Exchange Resins

Abstract

An adsorber consisting of hydrous titanium oxide (HTiO) dispersed in a Dowex-type ion-exchange resin matrix (designated RT resins) has been developed which is capable of removing Al(III)-based colloidal dispersions in the neutral pH condition. The effect of resin crosslinking, particle size, HTiO loading, turbidity level, and flow rate on the turbidity removal efficiency of RT resins has been studied. It is demonstrated that a train of columns comprising RT resin, H⁺, and OH^? form of resins could be used for large-scale purification operations at high flow rates. These columns, apart from removing turbidity and associated radioactivity, can effectively remove dissolved uranium present in ppb levels when used for water purification in nuclear reactors.     

Steam-pyrolysis activation of wood char for superior odorant removal

A pre-charred, wood-based carbonaceous precursor was activated using a two-step process (steam-pyrolysis activation) to investigate the potential for optimizing an activation protocol for the production of powdered activated carbon (PAC) tailored to effectively remove the taste- and odor-causing compound 2-methylisoborneol (MIB). Activation temperature, activation time, and steam-to-carbon ratio were the activation parameters modified to find the best operating conditions. The success of the tailored PACs was judged on performance in batch experiments, which were designed to simulate actual water treatment plant conditions and used natural water spiked with ¹⁴C-MIB. Activation temperature had the greatest impact on PAC performance, with 1123 K providing the best operating point. The pore size distribution data revealed a strong correlation between an increase in mesoporosity and MIB removal in the raw waters. In addition, the tailored PAC with the optimized activation protocol outperformed existing commercially available PAC, indicating the plausibility of tailoring activation protocols for superior MIB removal from natural waters.     

Extraction of Cesium from an Alkaline Leaching Solution of Spent Catalysts Using an Ion-Exchange Column

Abstract

The selective extraction of cesium from an alkaline leaching solution of spent catalysts using phenolic resins was studied. The resins were synthesized by alkaline polycondensation of formaldehyde by phenol, resorcinol, catechol, and phloroglucinol. Their ionoselectivities for five alkali metals were evaluated with a solid-liquid extraction, and their ion-exchange capacities were compared. The resin with the best selectivity for cesium was tested with a real solution at different pH values. An on-column extraction is proposed to obtain cesium with high purity.     

Hydration of 2-methyl-2-butene in gas-liquid cocurrent upflow and downflow reactors

An olefin (2-methyl-2-butene) gas and distilled water were fed either upwardly or downwardly into a fixed-bed reactor packed with strong acidic ion-exchange resins. Global reaction rates of olefin hydration were measured by changing gas and liquid velocities. The observed rates were interpreted by using a model in which the direct mass transfer from gas to solid occurred as well as the indirect mass transfer through the liquid phase.     

一种巯基胺型羧酸螯合树脂的制备及其吸附性能

以环硫氯丙烷和多乙烯多胺为原料,通过交联反应合成了巯基胺型树脂(PA树脂)。然后对PA树脂进行氯乙酸化反应,合成了巯基胺型羧酸螯合树脂(PAC树脂),并通过傅立叶变换红外光谱仪(FTIR)对其结构进行了表征。研究了PAC树脂对模拟含Cu2+电镀废水的吸附性能,探讨了树脂用量、吸附时间和pH对Cu2+吸附性能的影响。实验结果表明,在常温常压下,取25 mL浓度为10 mmol/L的废水溶液,PAC树脂吸附Cu2+的最佳用量为0.40 g/mmol Cu2+,最佳吸附时间为150 min,最佳pH为6~10,最大吸附量和最大吸附率分别达到2.53mmol/g和94.7%。PAC树脂对Cu2+的吸附过程符合Langmiur和Freundlich等温吸附方程。     

Ion-Exchange Selectivities of Periderm and Cuticular Membranes toward Alkali Cations

Abstract

The ion-exchange selectivities of lithium, sodium, potassium, and cesium on isolated potato periderm (solanum tuberosum) and pear fruit cuticular membranes were investigated; the general order of preference both for cation selectivities and ion-exchange capacities was lithium > sodium > potassium > cesium. The potato periderm and pear fruit cuticular membranes exhibited a behavior typical of ion-exchange resins of the weak acid type. At constant pH7, the ion-exchange capacities of periderm and cuticular membranes increased with hydrated ionic radius, and also with increasing pH and neutral salt concentration, and decreased with crystal ionic radius. Counterion selectivities also exhibited the same behavior. The ion-exchange properties are discussed in terms of the structure and function of potato periderm and pear fruit cuticular membranes.