Silica removal in industrial effluents with high silica content and low hardness

Latour, Isabel; Miranda, Rubén; Blanco, Ángeles

doi:10.1007/s11356-014-2906-8

Cited by 35 publications

(27 citation statements)

References 16 publications

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“…As shown in figure 2, the maximum COD removals were around 15% with all the products. These removal rates were similar to the ones obtained with soluble magnesium salts (MgCl2·6H2O and MgSO4·7H2O) at similar conditions as reported in a previous study [22]. Although significant, this decrease in COD values may not have a significant impact on the organic fouling in subsequent membrane treatments.…”

Section: 3-methodology For Jar-testssupporting

confidence: 89%

“…These pHs were selected according to previous studies with the same type of water [22]. Magnesium compounds were tested using NaOH as pH regulator.…”

Section: 3-methodology For Jar-testsmentioning

confidence: 99%

“…After 1 min of mixing at 200 rpm, the magnesium compound being tested was added and mixed for a period of 15 min at 200 rpm, according to previous studies [22], and then, the waters were allowed to settle for 1 h. Finally, the clarified waters and the dissolved fraction, obtained by centrifugation at 2000 g during 15 min in a Hettich…”

Section: 3-methodology For Jar-testsmentioning

confidence: 99%

“…However, this problem could be partially solved with the use of Ca(OH)2 as pH regulator [22]. Another approach would be reducing the total dissolved solid concentration (TDS) by using sparingly soluble magnesium compounds instead of soluble magnesium as tested in previous studies [22]. …”

mentioning

confidence: 99%

“…This high pH level needed was directly translated into an important increase in the conductivity of the waters, which could make necessary the post-treatment of the RO rejects and may compromise the economic feasibility of the whole effluent reuse treatment. However, this problem could be partially solved with the use of Ca(OH)2 as pH regulator [22]. Another approach would be reducing the total dissolved solid concentration (TDS) by using sparingly soluble magnesium compounds instead of soluble magnesium as tested in previous studies [22].…”

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confidence: 99%

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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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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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Section: 3-methodology For Jar-testssupporting

confidence: 89%

“…These pHs were selected according to previous studies with the same type of water [22]. Magnesium compounds were tested using NaOH as pH regulator.…”

Section: 3-methodology For Jar-testsmentioning

confidence: 99%

Section: 3-methodology For Jar-testsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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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Enhanced Silica Removal by Polyamine‐ and Polyacrylamide‐Polyaluminum Hybrid Coagulants

et al. 2015

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Silica removal is the main bottleneck for a high reuse of deinking paper mill effluents due to silica scaling on the reverse‐osmosis units generally used. The efficiency of inorganic‐organic hybrid coagulants formed by the combination of polyaluminum nitrate sulfate (PANS) with different dosages of cationic polyacrylamide (PAM) or polyamines (PA) on silica removal is analyzed. These hybrids significantly increased the silica and chemical oxygen demand (COD) removal at all pH values studied, with PA modification being the most efficient. While conventional aluminum coagulants allow high silica removal, only at both high pH and dosages the PA derivatives achieve high silica and soluble COD removal without pH adjustment. PAM hybrids only slightly improved the efficiency of PANS at the highest active contents.

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Study on the mechanism of PAMAM(DETA as the core) against silica scale

Wang

Liu

et al. 2021

J Mol Model

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Silica removal in industrial effluents with high silica content and low hardness

Cited by 35 publications

References 16 publications

Silica removal with sparingly soluble magnesium compounds. Part I

Silica removal with sparingly soluble magnesium compounds. Part I

Enhanced Silica Removal by Polyamine‐ and Polyacrylamide‐Polyaluminum Hybrid Coagulants

Study on the mechanism of PAMAM(DETA as the core) against silica scale

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