Removal Of Silica Research Articles

Membrane distillation of a silver leaching solution: Role of the coexisting aluminum ions on silica scaling

Silver, with excellent physicochemical properties, has been widely used in modern industry. Silver recovery from end-of-life product is economically significant for sustainability. However, silver leaching solution (SLS) containing diverse heavy metal ions as well as dissolved silica is a challenging waste stream for treatment and silver recovery. In this work we explored treatment of a real SLS via direct contact membrane distillation (DCMD). Results showed that silica scaling in DCMD process was closely related to the coexisting aluminum ions (Al3+) in SLS. The amount of Al(OH)3 formed was dependent on the initial pH of SLS and was effective to reduce concentration of the total dissolved silica in SLS, which was the key factor that influenced particle size distribution of SLS and degree of silica scaling. The highest silica removal rate of 83.7% was achieved at pH of 11. Moreover, it was found that the Al(OH)3 with positive charge accelerated mono-silicic acids aggregation, leading to prompt silica polymerization. This hypothesis was underpinned by evidence that amorphous yet compact aggregates formed on membrane surface and trimer silicates formed in the concentrated SLS with initial pH of 11. As a result, the most severe silica scaling occurred during DCMD treatment of SLS, resulting in the lowest initial permeate flux and water recovery. Our results shed light on prevention and management of silica scaling in treatment of waste stream.

Optimization of the removal of lignin and silica from rice husks with alkaline peroxide

Rice husks surround rice grains, and are known to provide them with a protective lignocellulosic cover. This biomass has many potential uses, such as biofuel production. However, the high concentrations of lignin and silica limit its use, for example, they hinder fermentation reactions. In this study, both the delignification and silica removal from husks using a combination of hydrogen peroxide and sodium hydroxide has been investigated. Response surface methodology has been used to find the optimum conditions for maximizing lignin and silica removal, and solid yield. Three independent variables, namely, NaOH concentration, H2O2 concentration and reaction temperature were studied by using Box-Behnken design. The first optimization focused on maximum removal of impurity, and was found at 8% NaOH, 1% H2O2 and 20 °C. Under such conditions, 71.78% lignin removal, 88.47% silica removal and 50.89% solid yield were achieved. The second optimization emphasized the reduction of chemical costs, and was found at 5.29% NaOH, 1% H2O2 and 20 °C; resulting in 59.85% lignin removal, 75.13% ash removal and 59.21% solid yield.

Understanding the Efficiency of Aluminum Coagulants Used in Dissolved Air Flotation (DAF)

This paper reports on the efficiency of five aluminum coagulants for the treatment of a paper mill wastewater by dissolved air flotation (DAF). The coagulants studied were: alum, a polyaluminum chloride coagulant of high aluminum content and intermediate basicity (PAC-MB), another with intermediate aluminum content and high basicity (PAC-HB), a polyaluminum nitrate sulfate of intermediate aluminum content and basicity (PANS) and one hybrid coagulant formed by the combination of PANS and a mixture of polyamines (PANS-PA). The influence of Al speciation on contaminants removal and the main flocculation mechanisms involved have been analyzed. High removal of suspended solids together with significant removal of dissolved and colloidal material (COD and silica) were obtained, which is required for extended reuse of this process water. PAC-HB was the best product for removing suspended solids (85%) and soluble silica (50%) with a rather limited COD removal (5%), while PANS-PA obtained high turbidity (90%) and silica removal (45%) together with a significant soluble COD removal (15%). Monomeric Al (Ala, Alm) was more efficient in removing suspended solids and soluble COD than polymeric or colloidal Al (Alc, Alu), but the latter was more efficient in removing soluble silica. Results demonstrated that the main flocculation mechanism varies with the aluminum dosage, being predominantly charge neutralization at low dosages and sweep flocculation at high dosages. The floc strength factor however, was very high and similar for all the coagulants and dosages tested (85–90%), as it was mainly determined by the behavior of the pre-flocculated suspended solids present in wastewater. The reflocculation factor varied from 45 to 75% at the lowest dosages to almost zero at the highest dosages, confirming the transition from charge neutralization to sweep flocculation. The flocs formed by PANS-PA had lower strength than the others and it decreased with the dosage while its reflocculation factor was almost zero, even at low dosages. Due to the polyamines present in this coagulant, its flocculation mechanism is through both charge neutralization and patch formation, especially at low dosages, and sweep flocculation and interparticle bridge formation at high dosages.

INFLUENCE OF TIME AND CONCENTRATION ON TEXTURAL PROPERTIES OF MESOPOROUS CARBONS OF GELATIN PREPARED BY HARD-TEMPLATING PROCESS

<p> </p><table class="data" width="100%"><tbody><tr valign="top"><td class="value"><p>Mesoporous carbons with different textural properties were prepared with gelatin by hard templating process. The effect silica removal condition (time and acid concentration) on the nanocomposite properties was studied during synthesis process. 1, 6, and 24 h silica removal times and 10%, 20%, 30% and 40% HF concentraton were chosen. Textural properties and microstructure of the nanocomposites were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDAX), and N2 adsorption– desorption. Results showed that removal silica time process led to mesoporous nucleation and growth on the surface of mesoporous carbon. At decreasing of removal silica time and HF concentration the surface area and total pore volume increased from 410 to 760 m2/g and 0.14–0.99 cm3/g with almost same of the average pore diameter considerably at 4.1 nm. Furthermore, it was observed more homogeneous pore distribution with decreasing the silica removal time dan HF consentration. In conclusion, the silica removal time and acid concentration play an important role on textural properties of mesoporous carbon which could have a major effect on adsorption properties of sulfuric compound in the fuel.</p></td></tr></tbody></table>

Silica removal by alkaline hydrogen peroxide treatment to enhance the conversion of rice straw to sugars

The massive production of rice straw could eventually lead to uncontrolled air pollution due to open burning activity. In this study, the rice straw was treated with alkaline hydrogen peroxide (AHP) to remove silica as well as to maximize the hydrolysis of the treated rice straw. Thus the study aimed to determine the effects of reaction parameters (i.e. AHP concentrations, particle sizes of rice straw, and temperature) towards the pretreatment with AHP in a batch system. From the characterization analysis, the rice straw sample contained high amount of silica (20%) and lignin (20%). From the study, >83.8% silica removal, 80% of delignification, and 7.88% of reduced sugar were achieved at optimum conditions of 60 °C with 10% AHP solution for sample with <0.5 mm particle size. From this study, the increase in AHP concentrations and temperature resulted in higher removal of silica and higher hydrolyzed sugar produced. Particle size did not caused significant effect towards the silica removal but contributed significantly towards the sugar production. Hence, it can be concluded that this study has depicted that the selected processes for silica removal from rice straw are indeed suitable to increase sugar production from biomass.

A Novel Mesoporous Carbon as Potential Conductive Additive for a Li-Ion Battery Cathode

A new mesoporous carbon (MC) is obtained from pyrolysis of resorcinol/formaldehyde resin, polymerized in the presence of tetraethoxysilane and Pluronic F108, followed by pyrolysis at 800 °C and silica removal. The reaction mixture in a molar ratio of 1F108/60resorcinol/292 formaldehyde/16900 H2O/50 tetraethoxysilane heated at 67 °C produces MC nanoparticles (200 nm average size) exhibiting 3D bimodal mesopores (3.9 and 8.2 nm), 1198 m2/g surface area, 1.8 cm3/g pore volume, and important graphitic character for use as a conductive material. Composites LiFePO4/carbon prepared with MC or commercial Super P, by the slurry method, were tested as coin Li-ion battery (LiB) cathodes. Super P (40 nm average particle size) exhibits better graphitic character, but lower porosity than MC. LiFePO4/MC shows better specific capacity (161 mAhg−1) than LiFePO4/Super P (126 mAhg−1), with a retention capacity (RC) after cycling at C/10 of 81%. Both composites with MC and Super P show well-distributed particles. According to impedance analysis, MC mesoporosity improves the charge transfer kinetics (CTK) more than Super P, producing a cathode with higher efficiency, although lithium ions’ diffusion decreases because larger MC particles form longer diffusion paths. Owing to the good specific capacity of the LiB cathode prepared with MC, research looking into improving its retention capacity should be a focus.

Eco-efficiency analysis of desalination by precipitation integrated with reverse osmosis for zero liquid discharge in oil refineries

In a process for industrial water reuse with zero liquid discharge (ZLD), a membrane separation step followed by an evaporative process is usually required. It is proposed here to maximize water conversion in the reverse osmosis (RO) membranes, in order to reduce the associated environmental impacts and economic costs from evaporative process. Considering a typical oil refinery wastewater with high inorganic scaling tendency, three ZLD virtual scenarios were proposed. A RO water recovery of 59% (default scenario SI) was increased to 89.2% with an upstream BaSO4 desupersaturation step (scenario SII). A 96.3% RO water recovery (SIII) was obtained adopting also a RO intermediate softening with CaO addition and calcite seeding, as well as MgSO4 dosing for additional silica removal. In all cases, the water not separated in the membrane was completely recovered in downstream evaporation and evaporative crystallization steps. A life cycle assessment (LCA) analysis suggests that the proposed scenarios enabled expressive reduction in the environmental impacts related to global warming, freshwater ecotoxicity and water consumption. Besides, it has been shown that the proposed scenarios were economically favorable. By means of an eco-efficiency analysis, economic, energetic and environmental implications appointed to benefits on developing of chemical precipitation techniques for a high RO desalting recovery in ZLD operations for aqueous effluents of petroleum refineries. It has also been found that some degree of intervention may lead to an improvement of all eco-efficiency indicators, but at some extent of intervention, at least some of the eco-efficiency indicators may become less favorable.

New model for particle removal from surface in presence of deformed liquid bridge

Despite the importance of removing particles from surfaces, particularly in the presence of liquid bridge, the process is yet to be investigated properly. In this research, this important process is explored and a mathematical model is presented that predicts the fluid velocity required to initiate the motion of a particle embraced by a liquid bridge. The model succeeds in incorporating (i) the liquid-bridge deformation due to the fluid flow and (ii) the associated detachment and lateral adhesive forces that depend on the surface characteristics. The model can also predict two types of particle motion, namely rolling and sliding. The removal of silica and ice particles is examined experimentally and the results are compared with the model predictions, thereby confirming the accuracy of the model. The present findings suggest a strong influence of the adhesive forces generated by the liquid bridge as the main forces resisting the removal of the particle from the surface. This study has implications in furthering the understanding of the underlying mechanisms during the removal of particles from surfaces exposed to fluid flow.

Polydopamine modified ordered mesoporous carbon for synergistic enhancement of enrichment efficiency and mass transfer towards phenols

Integrating the steps of direct carbonization, removal of silica and polymerization of dopamine, four ordered mesoporous carbons (OMCs) doping with different constituents were prepared and characterized successfully, which were proved to possess similar ordered mesopore structure, high surface area and different hydrophilic properties. Subsequently, a series of pollutants were selected as target analytes to investigate the enrichment capacities of as-prepared OMCs based on the technique of solid phase microextraction (SPME). It was found that the OMC modified with polydopamine (OMC@PDA) demonstrated outstanding performance towards phenols, since its hydrophilicity was enhanced by PDA. Moreover, two extraction modes were employed to study the extraction process, including headspace and direct immersion. The synergistic enhancement effect of enrichment efficiency and mass transfer towards phenols using the OMC@PDA-coated fiber was demonstrated in the mode of direct immersion. To realize the target of high sensitivity, the OMC@PDA-coated fiber was coupled with the gas chromatography-mass spectrometry (GC-MS) after optimizations to develop analytical method. Wide linear range (5–5000 ng L−1), low detection limits (0.08–0.38 ng L−1) and excellent reproducibility made the developed method feasible for the determinations of trace phenols in environmental water samples.

Silica Removal Using Magnetic Iron-Aluminum Hybrid Nanomaterials: Measurements, Adsorption Mechanisms, and Implications for Silica Scaling in Reverse Osmosis.

Composite magnetic aluminum hydroxide at iron oxide nanomaterials, Al(OH)3@Fe3O4, with a well-defined core-shell structure, were used as pretreatment adsorbents for the removal of silica in brackish water. The Al(OH)3 outer shell confers silica adsorption capacity, and the superparamagnetic Fe3O4 core allows material separation and magnetic recovery. The as-prepared nanomaterials (2 g L-1) remove ∼95 and ∼80% silica from Si-rich solutions with 0.5 and 2 mM initial silica concentrations, respectively. Regeneration under basic conditions was evaluated, and post-adsorption treatment with 0.05 M NaOH yielded optimal material reusability. After four regeneration cycles, the Al(OH)3@Fe3O4 nanomaterials retain their magnetic property while still being able to remove ∼40% silica from solutions at an adsorbent concentration of 2 g L-1. The mechanism of silica adsorption onto the surface of the nanomaterials was probed using several spectroscopic techniques. ATR-FTIR (attenuated total reflection-Fourier transform infrared) integrated with two-dimensional correlation analysis shows that silica species vary from Q2 to Q4 with adsorption time corresponding to silica polymerization. 29Si solid-state NMR spectra show an upfield chemical shift displacement of the Q2 signal, which indicates the formation of Q4 units, suggesting silica polymerization onto the Al(OH)3 shell. In addition, a laboratory-scale reverse osmosis setup was used to evaluate Al(OH)3@Fe3O4 as pretreatment materials for silica removal. Results show that silica scaling was significantly alleviated, and water recovery was enhanced when feed waters were pretreated with the magnetic nanomaterials. Taken together, our study highlights the promise of magnetic Al(OH)3@Fe3O4 nanomaterials in treating brackish water and achieving higher water recovery for inland desalination.

Fusion and chemical separation of Am, Pu and Sr from barite-concrete

The goal of this study was to omit the hazardous hydrofluoric acid for silica removal before fusion of barite-concrete. Furthermore, the goal was to establish a chemical separation technique to simultaneously determine the activity concentrations of 241Am, 238Pu, 239+240Pu and 90Sr of one sub-sample. After the fusion process, using Li-metaborate/Li-tetraborate, the colloidal silica could be successfully flocculated using polyethylene glycol (PEG-2000). A chemical separation scheme using the resins DGA—BIO-RAD AG 1-X2/UTEVA—DGA and TEVA for the actinides and DGA and Sr resin for Sr was successfully established, underlined by the quantitative 243Am, 242Pu and 85Sr average tracer recoveries of at least 60%, and in best cases up to 86%.

Removal of silica from brackish water by integrated adsorption/ultrafiltration process.

A lab-scale unit of the hybrid continuous stirred tank reactor (CSTR) adsorption/ultrafiltration (UF) system was used to evaluate the removal efficiency of silica from brackish water. The semi-batch adsorption process was carried out using iron oxy/hydroxide agglomerates (IOAs) as adsorbent and hollow fiber ultrafiltration membrane as a barrier to the adsorbent passage to the product water. The effect of residence time, concentration of silica, and adsorbent dosage on the silica removal and UF membrane blockage was examined. It was found that a short residence time of 15min was sufficient to achieve the maximum adsorption capacity similar to that obtained in batch isotherm experiments. The adsorption capacity increased with the augmentation of the silica concentration and decreased with the increase in the adsorbent dosage. The UF was effectively employed to separate the loaded adsorbent without fouling the membrane until breakthrough. A simple model was applied to accurately predict the adsorption breakthrough curves.

Abatement of hydrated silica and simultaneous removal of coexisting ions from deep well water by electrocoagulation using an up-flow reactor

The removal of hydrated silica and coexisting ions from groundwater (hydrated silica 42 mg L−1, fluoride 7.3 mg L−1, arsenic 40 μg L−1, sulfate 57 mg L−1, phosphate 0.26 mg L−1, pH = 8.02 and conductivity 605 μS cm-1) by electrocoagulation (EC) was examined. The EC was carried out in a novel up-flow reactor with a six-cell stack, in a serpentine array opened to the atmosphere, using aluminum plates as electrodes. The influence of current density (10 ≤ j ≤ 16 mA cm−2) and mean linear flow rate in the EC reactor (1.16 ≤ u ≤ 4.67 cm s−1), corresponding to retention times between 13.9 ≤ τ ≤ 55.9 s, on the hydrated silica, fluoride, arsenic, sulfate and phosphate removal was investigated. The best removal of hydrated silica based on energy consumption (0.98 KWh m−3) and overall cost of EC (0.274 USD m−3) was obtained at 12 mA cm−2 and u= 2.33 cm s−1, giving a remaining concentration of silica of 7 mg L−1, while the residual concentrations of fluoride (1.4 mg L−1) and arsenic (1.88 μg L−1) met the WHO guidelines in human drinking water. The characterization of the flocs by SEM-EDS, XRF, XRD and FTIR indicated that the coagulant reacts with silica to yield aluminum silicates, fluoride substitutes a hydroxyl group from flocs, while arsenates, sulfates, and phosphates are adsorbed on aluminum aggregates.

Arsenic and hydrated silica removal from groundwater by electrocoagulation using an up-flow reactor in a serpentine array

This paper concerns with the elimination of arsenic and hydrated silica from deep well water, collected form the septentrional area of Guanajuato in Mexico (arsenic 23 μg L−1, hydrated silica 154 mg L−1, sulphate 160 mg L−1, phosphate 0.3 mg L−1, pH 7.5 and conductivity 550 μS cm−1) by electrocoagulation (EC) using an up-flow electrochemical reactor, opened to the atmosphere, with a six-cell stack in a serpentine array. Aluminum plates were used as electrodes. The efficiencies of arsenic and hydrated silica removal at different current densities (4 ≤ j ≤ 7 mA cm-2) and mean linear flow rates (1.2 ≤ u ≤ 4.8 cm s−1) were examined. The best EC was obtained at 7 mA cm-2 and 1.2 cm s−1, which satisfies the WHO guideline for arsenic (< 10 μg L−1) and permits the abatement of hydrated silica, giving values of electrolytic energy consumption and overall cost of EC of 1.64 kW h m-3 and 0.387 USD m-3, respectively. SEM-EDS, FXRD, XRD and FTIR analyses on the flocs revealed that they are structured mainly by aluminosilicates due to the reaction between aluminum and silica. While arsenates, sulfates and phosphates are removed by adsorption on aluminum flocs.

Field validation of self-regenerating reversible ion exchange-membrane (RIX-M) process to prevent sulfate and silica fouling

Desalination of brackish water and municipal wastewater will be integral to water resource resiliency during uncertain climate conditions. Higher efficiency and higher recovery than conventional desalination is achievable if biofouling and inorganic scaling can be avoided on membranes or heating surfaces. Temporary hardness is well addressed through acid and antiscalant dosing, but permanent sulfate hardness lacks selective removal techniques that do not require external chemicals or produce large volumes of sludge. Self-regenerating reversible ion exchange-membrane (RIX-M) processes have been proposed using a tunable anion exchange blend to remove silica and sulfate selectively from influent water with efficient regeneration via brine reject. A 2.5GPM RIX-M process was tested at the US Bureau of Reclamation (USBR) Brackish Groundwater National Desalination Research Facility (BGNDRF, Alamogordo, NM). High sulfate-containing brackish groundwater was desalinated at high recovery (80%) without membrane fouling through selective sulfate removal and regeneration via desalination brine reject, without external chemical addition. Ten treatment-regeneration cycles were performed without degradation in system performance. High efficiency silica removal from complex groundwater backgrounds at BGNDRF was also achieved across varying water chemistries. RIX-M offers a new pre-treatment opportunity to protect RO membranes from sulfate and silica fouling without dosing anti-scalants, while attaining high recovery.

High benzene adsorption capacity of micro-mesoporous carbon spheres prepared from XAD-4 resin beads with pores protected effectively by silica

The aim of this work was to prepare micro-mesoporous carbon spheres with high specific surface area and large volume of mesopores from porous styrene-co-divinylbenzene ion exchange resin Amberlite XAD-4 beads. Prior to the carbonization step, the mesoporous resin beads were protected by silica formed via impregnation of tetraethylorthosilicate followed by its hydrolysis and condensation. This was essential to obtain highly porous carbon spheres after silica removal that featured the specific surface area up to 1050 m2 g−1 and total pore volume up to 1.35 cm3 g−1. Additional CO2 activation resulted in micro-mesoporous carbon spheres and consequently boosted their adsorption capacity for benzene up to 21–24 mmol g−1 at 20 °C and relative pressure close to unity. Moreover, carbon dioxide adsorption properties of the samples were studied, and the highest uptake of 4.5 mmol g−1 at 0 °C and 1 bar pressure was obtained for the activated carbon. Our findings indicate that the activated carbon spheres exhibit a great potential for capture benzene and related volatile organic compounds.

Lithium-ion capacitor using rice husk-derived cathode and anode active materials adapted to uncontrolled full-pre-lithiation

Rice husk (RH), agricultural waste produced from rice harvest, is investigated as a potential source for cathode and anode active materials in lithium-ion capacitors (LICs). A carbonized mixture composed of pre-heated RH and beet sugar is subjected to silica removal via immersion in NaOH solution followed by activation using CO2 gas. This yields activated carbon with a specific surface area of 1801 m2 g−1 as the cathode active material. The anode active material is produced by carbonizing RH and partly removing 41 mass% of silica. The charge-discharge performances of a three-electrode LIC full-cell, using the RH-derived cathode and anode active materials with Li metal as the reference electrode, are evaluated under the uncontrolled full-pre-lithiation in comparison with similar three-electrode LIC full-cells using a commercial cathode and anode (graphite or hard carbon) active materials. The results of charge-discharge tests reveal that excellent rate and cycling stabilities are obtained from the LIC using RH-derived active materials in comparison with those using commercial active materials. Postmortem material characterizations suggest that the performance stability of the RH-derived LIC is attributed to the passivation ability of silica for excessive Li delivered via the full pre-lithiation process.

UTEP–EPW university–utility partnership: Concentrate enhanced–recovery reverse osmosis process for high water recovery from silica‐saturated desalination concentrates

Since the 1970s, The University of Texas at El Paso and El Paso Water have had a synergistic university-utility partnership, and in 2002, we began a sequence of investigations of enhanced recovery of water from silica-saturated reverse osmosis concentrate: (a) two-pass nanofiltration (NF) and reverse osmosis (RO) treatment, (b) lime softening for silica removal, (c) vibratory shear enhanced processing (VSEP), (d) continuous-flow seawater RO treatment of brackish RO concentrate, and finally (e) high-recovery concentrate enhanced-recovery reverse osmosis (CERRO) process. Studies funded by El Paso Water, Texas Water Development Board, U.S. Bureau of Reclamation, and WateReuse Research Foundation were conducted at the Kay Bailey Hutchison (KBH) Plant in ElPaso and the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM, and showed that as much as 88% of the water could be recovered from silica-saturated KBH concentrate using the CERRO process. Full-scale implementation of the CERRO process at well sites in El Paso has resulted in 70%-75% recovery of RO concentrate with a specific energy consumption of 1.23kWh/m3 (4.6kWh/kgal) and total estimated cost of approximately $0.59/m3 ($2.25/kgal). Cost-effective high-recovery desalination technologies such as CERRO are essential for drought-proof water supply in arid cities such as El Paso. PRACTITIONER POINTS: This two-decade UTEP-EPW research partnership was sustained by a long-term commitment to research and consistent financial support from EPW. Universities can collaborate to leverage utility funding toward larger external grant funding to advance research and development in a win-win partnership. The high-recovery CERRO process was developed through multiple phases of concentrate management research, which would not have been possible without long-term research commitment and risk tolerance from EPW. CERRO systems are being implemented at full scale in El Paso to recover water from silica-saturated RO concentrate at an estimated specific energy consumption of 1.23kWh/m3 (4.6kWh/kgal) and total amortized cost of $0.59/m3 ($2.25/kgal).

110th Anniversary: Industrial Process Water Treatment and Reuse Enabled by Selective Ion Exchange Materials

Silica (SiO2) is ubiquitous in petroleum produced waters; removal and recovery of silica reduces fouling when upcycling these waters for industrial applications. Herein, we report the relevant properties of a selective silica recovery material, calcined hydrotalcite (HTC), as well as the design and economic analysis for its use in an ion exchange process to remove silica from produced water. This process improves upon established technologies by minimizing sludge product, reducing process fouling, and lowering energy use. The ion exchange capacity of HTC (approximately 45 mg SiO2/g HTC) and optimized thermal reaction conditions (550 °C for 30 min) for calcination and regeneration were determined experimentally and used in the process modeling. Modeling outputs included raw material requirements, energy use, and the minimum water treatment price (MWTP). Monte Carlo simulations for process economics showed how R&D improving HTC reusability and silica binding capacity as well as separate reductions in raw material price can decrease MWTP by 40%, 13%, and 20%, respectively.

Effective removal of silica and sulfide from oil sands thermal in-situ produced water by electrocoagulation

Effective removal of silica and sulfide from oil sands thermal in-situ produced water can reduce corrosion and scaling of steam generators, enhancing water recycling and reuse in the industry. The removal of these two solutes as well as calcium and magnesium (i.e., the solutes that can also cause scaling) from synthetic and authentic produced waters by electrocoagulation (EC) was investigated in this study. In Fe0-EC, the precipitation of FeS minerals resulted in a rapid removal of sulfide and adsorption of silica onto FeS. In Al0-EC, silica was removed via adsorption onto aluminum hydroxides, but sulfide was poorly removed. In both EC systems, Ca2+ and Mg2+ were removed from the organic-free synthetic produced water but not from the authentic water, likely due to the influence of organic species. Contaminant removals in Fe0-EC were controlled by charge density (q, C/L) but not current density (i, mA/cm2). Overall, this research suggests that EC can be a promising technology for the treatment of thermal in-situ produced water. Fe0-EC appears to be a better choice than Al0-EC considering that Fe0-EC was more effective at removing sulfide, and that Fe0 anodes are usually less expensive.