Use of antiscalants for mitigation of silica (SiO2) fouling and deposition: fundamentals and applications in desalination systems

Neofotistou, Eleftheria; Demadis, Konstantinos D.

doi:10.1016/j.desal.2004.06.135

Cited by 167 publications

(83 citation statements)

References 34 publications

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“…This makes the removal of silica a key factor for the reuse of the effluent to work on the RO membrane at recoveries higher than 20% [3] without scaling problems. Membrane fouling caused by silica is a bottleneck as silica scaling in RO membranes is severe and, once it is formed, it is very difficult to remove by chemical cleaning [6,7]. This scaling causes decline in water production rates, low permeate quality, unsteady-state operation conditions, higher energy consumption and serious damages in the membranes that shorten their lifetime, limiting the technical and economic feasibility of the whole treatment chain [8,9].…”

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confidence: 99%

Silica removal with sparingly soluble magnesium compounds. Part I

Latour

Miranda

Blanco

2014

Separation and Purification Technology

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The main bottleneck in the treatment and reuse of effluents from deinking paper mills that employ reverse osmosis (RO) is the high silica content, which causes membrane fouling that limits the recovery of the treatment. Silica removal with magnesium compounds enables to treat large volumes of water with high removal efficiencies at low cost. Although soluble magnesium compounds are efficient, their use is limited since they increase the conductivity in the treated waters. Therefore the use of sparingly soluble magnesium compounds might be a promising alternative. Three sparingly soluble magnesium compounds (MgO, Mg(OH)2 and (MgCO3)4·Mg(OH)2·5H2O) were studied in this paper at three pHs (10.5, 11.0 and 11.5) and five dosages (250-1500 mg/L) at ambient temperature (~20ºC). Only 40% silica removal was obtained, which is not high enough to work at regular RO recoveries without scaling problems. To increase silica removal, the slurries of sparingly soluble compounds were pre-acidified with concentrated sulphuric acid and tested at the same conditions. In this case, high removal rates were obtained (80-86%) at high pH (11.5), even at ambient temperature. These removal rates would allow working at 75-80% recovery in RO units without scaling problems. This pre-acidification, together with the use of Ca(OH)2 as pH regulator limited the increase of the conductivity of the treated waters to only 0.2 mS/cm. Additionally, the use of Ca(OH)2 instead of NaOH as pH regulator increased the chemical oxygen demand removal from 15% to 25%.Keywords: silica removal, magnesium, softening, pre-acidification, membrane, fouling, effluent reuse, paper recycling 2 1.-INTRODUCTIONPaper industry is one of the leading industries in water management and sustainable water use. Although different alternatives have been developed to optimize the use of water in papermaking, there are still some unresolved aspects that limit their implementation at industrial scale. The closure of water loops through the internal reuse of water is limited by the accumulation of contaminants, especially dissolved and colloidal material (DCM), which affects the paper machine runnability and the final product quality [1]. To further reduce water consumption it is therefore necessary to treat and reuse the paper mill effluents. Membrane treatments, such as ultrafiltration (UF) and reverse osmosis (RO) [2,3], allow to produce the water quality required to reuse the effluent. However, effluents from deinking paper mills are characterized by high silica content, ranging from 50 to 250 mg/L as SiO2 [2,4,5]. This makes the removal of silica a key factor for the reuse of the effluent to work on the RO membrane at recoveries higher than 20% [3] without scaling problems. Membrane fouling caused by silica is a bottleneck as silica scaling in RO membranes is severe and, once it is formed, it is very difficult to remove by chemical cleaning [6,7]. This scaling causes decline in water production rates, low permeate quality, unsteady-state operation conditions, higher ener...

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Silica removal with sparingly soluble magnesium compounds. Part I

Latour

Miranda

Blanco

2014

Separation and Purification Technology

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“…For example, %D values obtained in the presence of 1.0 mg/L PAA and PMAA are 33 and 20% respectively, compared to <5% obtained for polymers containing non-ionic groups i.e., PEOX, PVP, PAM. It is interesting to note that although PVP and PEOX exhibit poor performance as iron oxide dispersant, these additives however, has been shown to exhibit good to excellent performance for silica polymerization process [12,13]. Thus, it is clear that performance of additive as a dispersant and/or inhibitor depends on both the inhibitor architecture and nature of the particles to be dispersed and/or scaling system being inhibited.…”

Section: Synthetic Polymers Performancementioning

confidence: 99%

Iron oxide dispersants for industrial water systems: types, performance, and selection criteria

Amjad¹

2017

Int. J. Corros. Scale Inhib.

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Dispersion of solid particles separating out from fluids is very important for fouling due to deposition of unwanted materials. Dispersion and stabilization of suspended matter i.e., clay, silt, corrosion products, precipitating salts, etc., is often overcome by incorporating a dispersant in the water treatment formulation. In this paper a variety of non-polymeric, natural polyelectrolytes, synthetic, and hybrid polymers were evaluated for their efficacy as iron oxide (Fe 2 O 3 , hematite) dispersants for industrial water systems. Results reveal that performance of dispersants strongly depends on dispersant dosage, dispersing time, dispersant architecture, and the impurities present in water. Among the non-polymeric additives evaluated phosphonates perform better than polyphosphates. Surfactants (anionic, non-ionic) tested are ineffective iron oxide dispersants. Performance data on natural polyelectrolytes show that lignosulfonate exhibits better performance compared to humic, fulvic, and tannic acids. Based on the performance of synthetic polymers the order of effectiveness is: terpolymer > copolymer > homopolymer. Results on the impact of impurities (i.e., trivalent metal ions, biocides, hardness ions, etc.) suggest that these impurities show negative influence on the polymers performance. Discussion on dispersion mechanism and dispersant selection criteria is also presented.

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“…Preventive methods interact and modify silica so as not to allow it to deposit on membranes but they do not remove it. The use of antiscalants is probably the most common method [8,9], although their efficiency in highly contaminant waters is low. Besides, when treated water is reused in other process stages, as the process conditions can change significantly, scaling problems could appear once again.…”

Section: Introductionmentioning

confidence: 99%

Silica removal from newsprint mill effluents with aluminum salts

Latour

Miranda

Blanco

2013

Chemical Engineering Journal

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The main obstacle for the implementation of reverse osmosis (RO) in a treatment chain to reuse the effluent of a newsprint mill as fresh water is the high silica content of the water, which produces severe scaling on the membrane, thus, limiting its recovery. Coagulation is one of the preferred methods to reduce silica concentration. Five aluminum based coagulants have been tested at five dosages (500-2500 ppm) and three pHs (8.3, 9.5 and 10.5). All products showed their best efficiency at the highest dosage and pH, with the exception of alum, that was more efficient at intermediate dosages. A combination of a polyaluminum nitrate sulphate with a cationic quaternary polyamine (PANS-PA2), was the most efficient and versatile coagulant. It removed 97% of silica (5 ppm residual silica) at the optimal conditions (pH 10.5, 2500 ppm) and it was very efficient (76% silica removal) at pH 8.3, avoiding the need of any pH adjustment, and minimizing the conductivity and pH increase of the treated waters as well as obtaining some removal of the organic colloidal matter (≈25%).

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Use of antiscalants for mitigation of silica (SiO2) fouling and deposition: fundamentals and applications in desalination systems

Cited by 167 publications

References 34 publications

Silica removal with sparingly soluble magnesium compounds. Part I

Silica removal with sparingly soluble magnesium compounds. Part I

Iron oxide dispersants for industrial water systems: types, performance, and selection criteria

Silica removal from newsprint mill effluents with aluminum salts

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