Iron Oxide-Coated on Glass Fibers for Arsenic Removal

A highly efficient adsorbent for arsenic removal from water has been prepared by impregnating high surface area iron oxides on glass fibers. Arsenic in water can easily and efficiently be removed by this adsorbent, without the need to pre-oxidize As(III) to As(V). The iron oxides coated on glass fibers (IOCGFs) can remove both arsenic species well below EPA MCL (10 ppb). IOCGFs should have the following four additional advantages: greatly improved contact efficiency; higher adsorption capacity because of high surface area; low cost and easily available adsorbent since the starting reagents (FeCl₃ and NH₃·H₂O) and glass fiber are cheap and readily available; and high adsorption efficiency of As(III) and As(V).     

Arsenic removal from water by photocatalytic functional Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiO<Subscript>2</Subscript> porous ceramic

Fe₂O₃–TiO₂ porous ceramic (Fe/TiPC) beads with photo-catalytic performances and high adsorption capacities were prepared by a simple high temperature solid reaction and were applied for arsenic removal from drinking water. The microstructure and morphology of Fe/TiPC were characterized by X-ray diffraction and scanning electron microscopy. More than 90% removal ratio for As (III) and As (V) were respectively achieved by Fe/TiPC within 2 h under UV irradiation. The Langmuir capacity values of Fe/TiPC for As (III) and As (V) were 13.86 and 15.73 mg/g, respectively. In addition, Fe/TiPC could be reused for up to five times without significant reduction in the photocatalytic sensitivity and adsorption capacity aspects. Good catalytic oxidation performances and high adsorption capacities as well as a sample preparation for Fe/TiPC suggest that the composites may have practical prospects for the As (III) and As (V) removal from contaminated water.     

Development of polyethersulfone/polylactic acid-blended nanocellulose membranes for enhanced removal of methylene blue dye

Herein, adsorptive polyethersulfone/polylactic acid (PES/PLA) blends membranes with systematic concentrations of cellulose nanofibers (CNFs) (0.5–2.5 wt%) were developed via a modified phase inversion process for the enhanced removal of cationic methylene blue (MB) dye. To the best of our knowledge, this is the first time that such adsorptive membranes have been produced for potential use in wastewater treatment. The fabricated membranes were characterized for surface and cross-sectional morphology (scanning electron microscope), surface roughness (atomic force microscope), functionality (Fourier-transform infrared spectroscopy), thermal stability (thermal gravimetric analysis), wettability (contact angle measurements), antifouling behavior (flux recovery studies), and dye adsorption and reusability (adsorption and desorption tests). CNF incorporated membranes showed improved wetting properties, with contact angle decreasing from 76° in the pristine membranes to 48° in 2.5 wt% PES/PLA membranes. The membrane bulk porosity increased from 60.3% to 79.23%, while the pure water flux increased from 210.8 to 399.12 Lm⁻² h⁻¹. At optimal conditions, CNF-modified membranes removed >98% of MB compared with 8% removal by the pristine membranes. After five cycles of adsorption and desorption, the membrane with 2 wt% CNFs achieved over 70% dye removal showing excellent reusability properties. Adsorption followed pseudo-second-order and Freundlich models. The adsorption was attributed to electrostatic interactions between the negatively charged membrane surfaces and the positively charged dye molecules as well as through hydrogen bonding. Therefore, this work revealed that CNF-modified PES/PLA membranes can be used as adsorbents for the enhanced removal of organic pollutants in water treatment applications.     

Preparation and characterization of ceramic nanofiltration membrane prepared from hazardous industrial waste

Kiln rollers, which are widely used in ceramic tiles production, are usually subjected to surface grinding to remove the contaminations. The resulted fine powder is considered useless waste and a hazardous source of environmental pollution particularly as it contains health-threatening fine free silica. In the present paper, the grind waste from kiln rollers was reused as raw material in the fabrication of nanofiltration ceramic membrane. The samples of produced ceramic membranes were formed into disks by adding 15% (by weight) organic binder solution with 2% concentration, then pressed at 35 MPa, dried and fired at temperatures range from 1100°C to 1300°C for 1 hour soaking time. It was found that the best firing temperature to produce nanofiltration ceramic membrane is 1250°C, where the ceramic membrane provides high removal of turbidity and high monovalent, divalent, and trivalent salts separation percentage.     

As(III) removal from drinking water using manganese oxide-coated-alumina: Performance evaluation and mechanistic details of surface binding

This paper describes the arsenite [As(III)] removal performance of manganese oxide-coated-alumina (MOCA) and its interaction with As(III) in drinking water. MOCA was characterized by XRD, SEM, EDAX, gas adsorption porosimetry, and point of zero charge (pH_pzc) measurements. Raman spectroscopy coupled with sorption experiments were carried out to understand the As(III) interaction with MOCA. As(III) sorption onto MOCA was pH dependent and the optimum removal was observed between a pH of 4 and 7.5. The Sips isotherm model described the experimental equilibrium data well and the predicted maximum As(III) sorption capacity was 42.48 mg g⁻¹, which is considerably higher than that of activated alumina (20.78 mg g⁻¹). The sorption kinetics followed a pseudo-second-order equation. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by MOCA was found to be a two-step process, i.e. oxidation of As(III) to arsenate (As(V)) and retention of As(V) on MOCA surface, with As(V) forming an inner surface complex with MOCA. The results of this study indicated that MOCA is a promising alternative sorbent for As(III) removal from drinking water.     

Adsorption characteristics of arsenic and phosphate onto iron impregnated biochar derived from anaerobic granular sludge

Biological wastewater treatment produces biowaste (sludge), which contains a high portion of organic matter. The organic matter comes from microorganisms, and the biowaste can be converted into biochar, a carbon-rich, fine-grained, and porous substance. Granular sludge from upflow anaerobic sludge blanket contains more organic matter (80 wt% of dry matter) and carbon content (>50% of organic matter). In this study, iron impregnated biochar was prepared to remove arsenic (As) and phosphate, oxyanionic pollutants, from the aqueous phase. The iron impregnation of biochar was executed in a one-step by pyrolyzing the biowaste in the presence of Fe instead of conventional two-step, i.e., biochar production after then modification. The granular sludge biochar and activated sludge biochar did not adsorb at all As and phosphate. The adsorption capacity of granular sludge biochar was enhanced via iron impregnation, and the iron-impregnated granular sludge biochar removed 10.37 mg PO ₄ ^3- /g, 11.5 mg As(V)/g, and 6.1 mg As(III)/g, respectively. Therefore, the one-step process enhanced the adsorption capacity and reduced processing time for the adsorbent synthesis.     

Preparation and characterization of polyvinyl chloride based nanocomposite nanofiltration-membrane modified by iron oxide nanoparticles for lead removal from water

In this research (polyvinyl chloride-blend-cellulose acetate/iron oxide nanoparticles) nanocomposite membranes were prepared by casting technique to lead removal from wastewaters. The effect of blend ratio of polymer binder (PVC to CA) and Fe₃O₄ nanoparticles concentration on physico-chemical characteristics of membranes were studied. Water permeability and ionic rejection tests, water content and mechanical properties measurements and SEM analysis were carried out in membranes characterizations. Obviously, modified membrane containing 10 wt% CA and 0.1 wt% Fe₃O₄ nanoparticles showed better performance in lead removal compared to other modified membranes and also pristine ones.     

Removal of Trace Arsenic to Meet Drinking Water Standards Using Iron Oxide Coated Multiwall Carbon Nanotubes

This study presents the removal of trace level arsenic to meet drinking water standards using an iron oxide-multi-walled carbon nanotube (Fe-MWCNT) hybrid as a sorbent. The synthesis was facilitated by the high degree of nanotube functionalization using a microwave assisted process, and a controlled assembly of iron oxide was possible where the MWCNT served as an effective support for the oxide. In the final product, 11 % of the carbon atoms were attached to Fe. The Fe-MWCNT was effective in arsenic removal to below the drinking water standard levels of 10 μg L(-1). The absorption capacity of the composite was 1723 μg g(-1) and 189 μg g(-1) for As(III) and As(V) respectively. The adsorption of As(V) on Fe-MWCNT was faster than that of As(III). The pseudo-second order rate equation was found to effectively describe the kinetics of arsenic adsorption. The adsorption isotherms for As(III) and As(V) fitted both the Langmuir and Freundlich models.     

Modelling arsenic(III) adsorption from water by sulfate‐modified iron oxide‐coated sand (SMIOCS)

A medium developed by coating BaSO₄ and Fe on quartz sand known as sulfate‐modified iron oxide‐coated sand (SMIOCS) was evaluated for the removal of arsenic(III) from simulated water with an ionic strength of 0.01 M NaNO₃ during batch studies. The medium was characterised for BET surface area, alkali‐resistance, acid‐resistance and the presence of iron and barium on the coated surface. Two simplified kinetic models, ie active available site (AAS) and chemical reaction rate models, were tested to investigate the adsorption mechanisms. The values of rate constants for both the models were found to decrease with increasing As(III) concentrations in the solute. The inverse relationship of rate constants of the reaction rate model with BET surface area showed that As(III) adsorption on SMIOCS was not due to physisorption but to chemisorption. A study of the effect of solute temperature showed that the adsorption of As(III) on SMIOCS media was due to chemisorption. The results of isothermal studies conducted at different pH values showed that adsorption data satisfied both the Langmuir and the Freundlich isotherm models. The adsorption of As(III) on the medium was pH dependent and maximum removal was observed in the pH range of 7–9. © 2002 Society of Chemical Industry     

Removal of As(V) Using an Iron-Impregnated Ion Exchange Bead

The ability of an iron-impregnated ion exchange bead (PWX5) to remove As(V) from ground water was investigated. The effects of particle size, solution pH, As(V) concentration, competition, adsorbent concentration, temperature, iron content, and iron accessibility on removal kinetics and/or equilibrium were determined. PWX5's performance was compared to other iron-based adsorbents, primarily Bayoxide® E-33 (E-33), a granular ferric oxide, for arsenic removal performance. All of the factors cited impacted either the amount of As(V) adsorbed or the rate of adsorption. Stirred batch reactor data showed the rate of adsorption increased as particle size decreased and bottle point isotherm data showed As(V) adsorption maximum capacity increased with higher initial adsorbate concentration. The presence of phosphate and silicate reduced the amount of As(V) adsorbed as did a pH > 7.0. PWX5 is durable, rather homogeneous in size and effective at removing As(V). It is a viable alternative to E-33 which has a wider size distribution and wears more easily.     

Al2O3/Yttria‐Stabilized Zirconia Hollow‐Fiber Membrane Incorporated with Iron Oxide for Pb(II) Removal

Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al₂O₃/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe₂O₃ was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe₂O_3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours.     

Preparation of SiO2/Si3N4 ceramics with step gradient porosity and heavy metal ion adsorption

Microporous ceramics with slag gradient distribution were prepared by interlayer bonding methods, using silicon dioxide and silicon nitride as the main raw materials. The material performances of gradient ceramics and uniform ceramics were discussed, and the adsorption effects of Cd (Ⅱ), Pb (Ⅱ) between them were compared. The experimental results show a flexural strength of gradient ceramics of 10.67 MPa, bonding strength of the bonding layer of 15.28 MPa, and only a 0.89% difference in the line shrinkage of the gradient layer of different slag contents, indicating that it is feasible to utilize interlayer bonding methods to prepare gradient ceramics. The maximum adsorption quantity of Cd (II), Pb (II) of gradient ceramics can reach 3.48 mg/g and 4.40 mg/g, respectively. For an average slag content of 17.5 wt%, gradient ceramics exhibited high permeability flux equivalent to ceramic with 25 wt% slag content and heavy metal adsorption amount equivalent to ceramic with 20 wt% slag content. Overall, the gradient ceramics prepared by interlayer bonding method can effectively improve the removal efficiency of adsorbent and the overall filtration efficiency.     

致密超细球形氧化铝制备性能良好的陶瓷超滤膜

热等离子体制备的超细球形氧化铝具有表面致密光滑、分散性好等特点,本工作以超细球形氧化铝为原料,通过浸渍提拉烧结法,制备了孔径分布窄、渗透通量高的陶瓷超滤膜,研究了烧结温度对陶瓷膜微孔结构的演化、孔径分布和渗透通量的影响。随后对1250℃下烧结的陶瓷膜进行了纳米硅水分散液过滤处理,采用不同堵塞模型分析了陶瓷膜过滤纳米硅水分散液的膜污染过程。结果表明,通过调节烧结温度调控陶瓷膜的微孔结构,当烧结温度为1250℃时,陶瓷膜的孔径分布较窄,孔径大小为25?65 nm,渗透通量为986.4 L/(m2?h)。超细球形氧化铝粒径分布较窄及表面致密光滑有助于1250℃下烧结形成均匀的烧结颈,提供了陶瓷膜较窄的孔径分布。对1250℃下烧结的陶瓷膜进行了纳米硅水分散液过滤处理后其浊度下降为0.231 NTU,浊度去除率达99.96%。采用不同堵塞模型分析了陶瓷膜过滤纳米硅水分散液的膜污染过程,结果表明,纳米硅水分散液的堵塞模型是滤饼过滤,属于可逆污染。     

Ceramic membrane synthesis based on alkali activated blast furnace slag for separation of water from ethanol

The main purpose of this research is synthesis of zeolite ceramic membranes based on alkali activated blast furnace slag for pervaporation separation of ethanol/water mixture (90 wt%). A new and simple method was applied to fabricate these ceramic membranes. In addition, gross waste of steel industry (blast furnace slag) was firstly used as the main starting material for making the membranes. In this study, for making the zeolite ceramic membranes, some experiments were conducted with water levels of 38, 40, 42 and 44 wt% of the blast furnace slag and NaOH levels of 4, 4.2, 4.4 and 4.6 wt% of the blast furnace slag. At first, for making the membranes, a primary geopolymer gel was prepared. Afterward the membranes were cast at 25 °C for 24 h. In order to form the zeolite layer, the membranes after geopolymerization process were kept at 90 °C for 24 h. The maximum value of selectivity (2579.48) was obtained for separation of water from ethanol using the synthesized membrane with 42 wt% water and 4 wt% NaOH.     

Dispersion of FeOOH on Chitosan Matrix for Simultaneous Removal of As(III) and As(V) from Drinking Water

Bio-inorganic chitosan based spherical shaped beads were prepared by dispersing rod-shaped FeOOH nanoparticles into a chitosan matrix for the removal of pure As(III) and As(V) from aqueous media, such as drinking water. A homogeneous mixture of chitosan and ferric nitrate, ferric chloride was prepared respectively with or without oxalic acid. The mixture was added dropwise in to a NaOH bath, where iron salts reacted with NaOH to form FeOOH particles. The scanning electron microscopy (SEM) showed that rod shaped FeOOH particles were distributed homogenously in the chitosan matrix. Diffuse reflective UV-vis (DRUV) spectra revealed that hydrated iron oxide formed a complex with functional groups in chitosan. Adsorption of As(III) and As(V) on different iron salt based bead was found to be pH dependent. The bead prepared from iron nitrate showed better performance for arsenic removal from aqueous solution over the bead that was prepared using iron chloride salt. The bead prepared using chitosan and iron-FeOOH is known as a chitosan-iron oxyhydroxide (CFOH) bead. The CFOH beads were found to be more efficient in removing As(III) from the solution compared to As(V). The adsorption of As(III) and As(V) from aqueous solution on CFOH beads was studied under equilibrium conditions in the concentration range of 1 mg/L to 50 mg/L in the presence of 0.05 M NaNO₃ at pH 6.5 and 298 K temperature. The maximum adsorption capacity of the CFOH bead was found to be 5.4 mg/g for As(V) and 7.2 mg/g for As(III) using the Langmuir equation. The presence of sulphate, phosphate, and silicate in aqueous solution had no effects on adsorption of either As(III) or As(V) on CFOH beads but decreased significantly at pH> 8.     

Strong adsorption of arsenic species by amorphous zirconium oxide nanoparticles

A novel oxide adsorbent of amorphous zirconium oxide (am-ZrO₂) nanoparticles was synthesized by a simple hydrothermal process for effective arsenic removal from aqueous environment. Due to their high specific surface area (327.1 m²/g), large mesopore volume (0.68 cm³/g), and the presence of high affinity surface hydroxyl groups, am-ZrO₂ nanoparticles demonstrated exceptional adsorption performance on both As(III) (arsenite) and As(V) (arsenate) without pre-treatment at near neutral condition. At pH ～ 7, the adsorption kinetic is fast and the adsorption capacity is high (over 83 mg/g for As(III) and over 32.4 mg/g for As(V), respectively). Under low equilibrium arsenic concentrations (C_e at 0.01 mg/L, the maximum contaminant level (MCL) for arsenic in drinking water), the amount of arsenic adsorbed by am-ZrO₂ nanoparticles is over 0.92 mg/g for As(III) and over 5.2 mg/g for As(V), respectively. The adsorption mechanism of arsenic species onto am-ZrO₂ nanoparticles was found to follow the inner-sphere complex mechanism. Testing with arsenic contaminated natural lake water confirmed the effectiveness of these am-ZrO₂ nanoparticles in removing arsenic from natural water. The immobilized am-ZrO₂ nanoparticles on glass fiber cloth demonstrated an even better arsenic removal performance than dispersed am-ZrO₂ nanoparticles in water, paving the way for their potential applications in water treatment facility to treat arsenic contaminated water body without pre-treatment.     

Optimizing adsorption of arsenic(III) by NH2-MCM-41 using response surface methodology

Response surface methodology (RSM) was used to optimize process parameters for arsenic (As(III)) removal from aqueous solution using amine-functionalized MCM-41 (NH₂-MCM-41). Four independent variables such as pH, initial metal concentration, temperature and adsorbent dosage were investigated. The optimal conditions to remove As(III) by NH₂-MCM-41 was found to be pH 5.62, initial As(III) concentration 5.00 mg/L, temperature 20 °C and NH₂-MCM-41 dosage 5.00 g/L. XRD, FTIR and SEM analyses testified to the obvious change of the surface morphology and the presence of metal on the sorbent after adsorption.     

Preparation Polyelectrolyte Complexes of Chitosan-Polyacrylic Acid-Modified Iron Sand Leachate for Proton Exchange Membranes

ABSTRACT

Polyelectrolyte complex (PEC) of chitosan (Chi) and poly (acrylic acid) (PAA)-modified iron sand leachate were prepared and considered for applicability as a proton exchange membrane in fuel cells. Chi-PAA-hematite blended in different weight ratios and the resulting membranes were treated to enable the formation of the polyelectrolyte. The membranes of Chi-PAA polyblend were treated using iron sand leachate and reveal high ion exchange capacity (IEC), proton conductivity, water uptake, and good mechanical stability. The result of research indicated that the membrane with 40 wt% of Chi and 60 wt% of PAA blend which its conductivity of 6.10 × 10^?2 S cm^?1 was potentially for a proton exchange membrane in fuel cell applications.     

Arsenic (V) removal with nanoparticulate zerovalent iron: Effect of UV light and humic acids

Results on As(V) removal in the presence of oxygen using the zerovalent iron technology with commercial iron nanoparticles (NanoFe^®) are presented, showing the effect of (NanoFe^®) mass, UV light and addition of humic acids. The nanosized iron particles (NZVI) were characterized in their particle size, surface area and constituent phases. As(V) removal was rapid and increased with NZVI mass (0.005–0.1 g L⁻¹) attaining more than 90% after 150 min of time contact with the optimal NanoFe^® concentration. The removal followed a biexponential kinetic decay, with rate constants increasing with NZVI mass. (NanoFe^®) presented an outstanding ability to remove As due to not only a high surface area and low particle size but also to a high intrinsic activity. Humic acids (HA) decreased around 50% the removal efficiency in the dark, indicating competition with As(V) for active surface sites. In contrast, UV light doubled removal rates, the process being even more enhanced in the presence of HA, with an almost total arsenic removal within 4 h. In all cases, adsorption on iron corrosion phases was found the main mechanism of As(V) removal, promoted by formation of Reactive Oxygen Species and enhanced under UV irradiation by the formation of multiple active species. Preliminary results with As-polluted groundwater of the Chacopampean Plain of Argentina (Tucumán Province) are also reported. Addition of NanoFe^® under UV irradiation for 3 h resulted in As contents well in agreement with the regulations (<10 μg L⁻¹).     

A cost‐effective crosslinked β‐cyclodextrin polymer for the rapid and efficient removal of micropollutants from wastewater

Water pollution problems pose a serious threat to the health of humans and other living organisms due to the increasing global contamination of various water resources by organic micropollutants, such as plastic components, dyes and pesticide intermediates. It has been a challenging problem to remove these organic micropollutants, despite various attempts. Here, we report a novel, cost‐effective and water‐insoluble crosslinked β‐cyclodextrin polymer for the efficient removal of various organic micropollutants from wastewaters with excellent adsorption capacity, large removal rate, robust performance and reusability. This polymer can remove 93% of bisphenol A within 1 min with an equilibrium uptake of 38 mg g^?1 and a maximum adsorption capacity at equilibrium of 139 mg g^?1. This is the fastest removal performance that has been reported so far, showing a bright future towards practical applications. © 2019 Society of Chemical Industry