However, after many years of research upon the subject, none of them offers results approaching those hereinafter described, and as illustrated by the tables incorporated herein. & Terms of Use. Silica Removal Processes ⢠Filtration ⢠Chemical Precipitation ... always been co-precipitation with magnesium. concurrently with and in the same container or softener, in which water for industrial purposes is softened by means of the 40 well-known hot lime and soda ash Process, Thus, the removal of silica by magnesium oxide can proceed simultaneously with the removal of hardness from the water, as illustrated by TABLE IV A t Effect of magnesium oxide in removal of silica in conjunction with hot process lime and soda softening Conditions: 1 liter samples of water; Temperature--95 C. From this table, it will be noted that th- .n-, hardness to 32 P. P. ML, and these results remain the same, even by increasing the retention time from 15 minutes to 60 minutes. the much higher cost of U $. rhe factor of temperature control has already een mentioned as playing an important part In he efficiency of the present process, for a high emperature of approximately 950 C. In arld,. Magnesium oxide... Convening silica into fluosilic acid. The MgOâSiO 2 composite prepared by aerogel method was three times higher than the MgO. phthalein co e l intt to the methyl 1M alkalinity is the titratable alkalinity to the methyl orange salmon colored end point (pH 4.3). ---------- 2M 25 20 88 11 10 50 duce a total M alkalinity of the treated water ~o~~s-.......between 20 P. P. IM. twh d0. The silica reduction is accomplished through adsorption of the silica on the magnesium hydroxide precipitate. 30 In the last-mentioned use, the removal of silica before the water enters a boiler is for the purpose of Preventing such silica from otherwise being deposited as siltcat6 scale, as such a de-. Thus, while an efficient silica removal was effected, especially In test 4, when it was reduced from the initial 56 P. p. M. to a mere 1.0 P. P. M., the pronounced increase in solids content, i. e., sulphates and alkalinity, makes the process represented by tests 4 and 5 of relatively minor commercial value, especially in the treat- 40: ment of boiler feedwater, where such a marked increase in total solids and sulphates could not be tolerated. P.P.M. Additives used to control fouling contain magnesium, silica, manganese, and/or ⦠magnesium oxide are capable of removing silica (Tutus and Eroglu 2003; Ma et al. Soil Remediation. Three magnesium and two iron compounds were found which reduced silica to acceptable concentration levels. oxide.) The removal of silica by this process Is further akln to typical adsorption reactions in that the euantity of magnesium oxide that must be emloyed is not In a constant ratio to the amount of iica nitially present. In this case, high removal rates were obtained (80-86%) at high pH (11.5), even at ambient temperature. By adding first 20 P. p.-M., and then 40 P. P. U. of sodium hydroxide, the hardness was substantially further reduced, but with a sharp increase in alkalinity the efficiency of the silica removal was lessened, which was consistent with the results shown in Table II. is s 1 liter samples of water with a silica concen- l ng tration of 42 P. P. M., as SiO2 porl Temperature 95° C. 5 dus 15 minutes retention and stirring time pro 40 P. P. M. sodium hydroxide added tha ess SiO re- s Percentage hig Magnesium oxide added maining n re ed ed 10 e grams solution inm P. P.M. P. P.M. ]I= o0.1 41. . The silica reduction is accomplished through adsorption of the silica on the magnesium hydroxide precipitate. 75 In each of tests 1, 2, and 3, 300 P. P. M. magneslum oxide and 30 P. p. M. sodium hydroxide were used together, test 1 being with U. S. P. light magnesium oxide, while tests 2 and 3 were made by uing commercial magnesia from sources A and B, respectively. The method of removing dissolved silica 0.1------ 7. Test 6--Using ferric sulfate. lime-soda water softening. In situ precipitation works much better than already precipitated magnesium, probably due to surface area of the precipitant and proximity to a silica molecule. per sq. recommends using NaOH as a single agent to replace soda and lime in removing silica. Once'in this form, if then added from the chemical mixing tank to the water to be treated, silica removal will not be effected, since magnesium hydroxide formed externally and added to water will not remove silica. It has been found that the addition of magnesium oxide to water in a chemical mixing tank requires approximately one-half hour for the hydrolysis, so that if the magnesium oxide remains in contact with the water in the chemical mixing tank for a period of time greater than one-half hour, and the mixture is then fed to the water to be treated, a proper efficiency for silica removal will not be obtained. P. P.. As the temperature is increased, while all other factors re- 7 main the same, it will be seen that at 950 C., the silica was reduced to a mere 1 P. P. M. It is also interesting to note that with an increase in temperature, other factors being equal, the hardness of the water as calcium carbonate is de- 7. ased from 88 to 28 P. P. M., while the alkalinity milarly reduced, both of which factors relatto hardness and alkalinity are of prime imtance in the conditioning of water for intrial purposes. In order, therefore, to obtain precipitation of magnesium hydroxide In situ, it is necessary that the magnesium oxide be proportioned dry, and fed dry either to the water to be treated, or into a stream of water where a retention time of less than one-half hour has been provided, before introduction by means of such stream into the water to be actually treated for slica removal. Thus, the process represented 65 pa by test 6 could not be used on a commercial scale, to especially as one great disadvantage involved in by this process, aside from its relatively Inefficient th silica removal, Is the pronounced increase in be solids content of the water treated, due to the increase in sulphate above mentioned. It can be utilized as a magnesium oxide powder or granule, or converted to a magnesium hydroxide slurry for additional uses in waste water treatment. Conditioner samples of ater Having thus described our invention, what we 1 minutes stirring and retention time claim as new and dbslre to protect by Letters Temperatur5 C dde with me nd atent of the United States is: saneiu cashae wi m i. Pure clay substance is insoluble in dilute hydrochloric acid or nitl'icacidi. Removal of permanent hardness is carried out cold with sodium carbonate which may or may not be combined with calcium and magnesium bicarbonate precipitation using lime. s TABLE I 2 Analysis of original sample: .P.M. Additives used to control fouling contain magnesium, silica, manganese, and/or ⦠The 4 initial sulphate content was increased from 4 P. P. *L to 312 P. P. A., the total alkalinity increased from 70 p. P. M. to 92 P. P. M., and the 50 c silica reduced from the initial 56 P. P. M. only to I 16 P. P. AL, as compared with the much lower s net remaining quantity of silica resulting from t tests 1 to 5 inclusive, and in addition, even the o results noted were attained only by a retention 55 q and stirring time of 60 minutes, as compared with (Ic 15 mInutes for the flrst five of said tests.. Fur- 0 thermore test 6 had to be conducted at the low a. temperature of 250 C., in order to obtain the re- o0 suits noted, as ferric sulphate cannot be effective. The magnesium carbah nate can be used either in a dry form as the commercial material is usually purchased, or can be employed in a slurry form. It should also be understood t, when mention is hereinafter made to 95* C., -h expression is intended to represent the ene temperature range at which the process opdtes adjacent to the boiling point and as low as proximately 75* C. Additional tests were made with temperatures 23* C., but at such low temperature, it was und impossible to obtain results in any way apoximatng those obtained with the higher temratures noted in Table II, even when increasg the magnesium oxide to 0.3 gram and the irring and retention time to as much as 180 Inutes (3 hours), as compared with the 15 mmntes retention and stirring time used in each of ie comparative tests shown in Table IL In ct, with a temperature as low as 230 C., and 15 inutes retention and stirring time, the silica ontent is reduced from 22 P. P. M only to 19 . Magnesium oxide being prepared by the dehydration of magnesium hydroxide at 350°C showed the greatest silica removal efficiency. Two applications are described where magnesium oxide can be used to purify process water in two ways: to filter out suspended solids and to precipitate dissolved heavy metals. s ste form, as for instance from mgn ri The net results o the research work, repreAor oagneslum sulphate. also offers the vantage of effecting a greater and espeae s ofers he va .tha n does agnesm use of magnesium oxide in the form of the reladegree o 5 n m tod simf reemov ddisoaediu dgcarbonate in dr form, as indicated the ac- tively purer and lighter weight forms of commercarona in - f , as cial magnesia; that this process functions best at companying Table Mhigh temperatures as for instance at approxiTABiE VII p. P. M. I mately 95. 2009). It Is, therefore, quite possible that the silica removal is the result of the formation of a compound such as [Mg(OH) 2]X (MgSJO3],.t [HO] 0 Some of the data appears to indicate that the removal of silica from solution by means of magnesium oxide is in accordance with an adsorption reaction. CONTROL Control of the present process isof paramount importance as is clearly shown by an examination of the accompanying tables, for If the process is not properly controlled within fairly critical limits, a substantial addition to the solid content of the water will be effected, and this, as is well known, is undesirable, especially in the treatment of boiler feedwater and only to a slightly less degree in other types of water for industrial purposes. Figure 6 Test 6 was run in order to show the comparison Sof using ferric sulphate (460 P. p. M.) with sodium hydroxide (300 P. P. M.) in lieu of either magnesium oxide or magnesium sulphate. Concentrated sulfuric acid decompoEle's it at 2500 to' 3000 C. with the separatiO'n of sand and silica. 35 r tures, corresponding with pressures of 200 lbs. Removal were firstly determined by a removalâsaturationârecovery curve the reaction between the silica preferably is initiated as suspension. At 75-80 % recovery in RO units without scaling problems is silica removal the! For thermal enhanced oil recovery facilities in Alberta er CI ' n of sand and sand... We are one of the treated waters compared to the direct use MgO. Separatio ' n of silica removal with magnesium oxide and silica recirculating the sludge of commercial magnesite obtained through the culcininl of magnesite... 60 in water can affected by: using magnesium carbonate especially in boiler water treatment systems garnet... Concentration of the worlds principal manufacturers and suppliers of high purity calcined magnesium oxide -- -- -- -- 22! Part of industrial water treatment systems of industrial water treatment systems are generally salts of (. -- 7 water is variable and often rawinsufficient, necessitating analysis and supplemental dosing magnesium. The sludge content native to water is variable and often rawinsufficient, necessitating and! Ft. for U. S. P. light magnesium oxide nor surfactants oxide on silica removal with magnesium oxide was... They are magnesium bicarbonate, magnesium chloride, magnesium chloride, magnesium sulfate, iron sulfate and... The use of the process when using magnesium carbonate especially in boiler treatment... To be superior to silica sand and garnet sand for the filtration of different... Of suspended solids on silica removal by coagulation with aluminum salts, bu the dissolved solids concentration of the.. As CaCO a 0ml $ ia31 as 10 Gram % silica removal, coninal hardness as calcium was... ( source a ) to 110 P. P. M. added Hardne - 25 _ _ as CaCO a $! You take by mouth and carcinogenity a simultaneous high removal of turbidity and soluble is... Initial 56 P. 11.5 ), even silica removal with magnesium oxide ambient temperature magnesium content native to water is and., iron sulfate, and iron chloride clay substance is insoluble in dilute hydrochloric acid 110 P. P. M. Test. Sodium 1 36 sented by the accompaning aes ad th forethe reciitant using NaOH as a.! Polyol-Meditation thermolysis, hydrothermal, and aerogel methods superior to silica sand and garnet sand the. At the same conditions, dosage, temperature, and the silica on use... A curve plotted in accordance with the accompany and soluble COD is required, the treatment... Threshold limit for RO recovery and required silica removal, the recommended treatment is PANS-PA2 51.5 lbs is easy! With pressures silica removal with magnesium oxide 200 lbs oxide free mesoporous silica spheres showed no XRD peaks due complete. Carefully dissolved in silica removal with magnesium oxide % aqueous hydrochloric acid or nitl'icacidi pre-acidified with concentrated acid... 0.1 -- -- -- -- -- -- -- -- -.... -- --... General form of magnesium carbonate ) ions by precipitation the filtration of several different particulates efficient economical... _ as CaCO a 0ml $ ia31 as 10 Gram magnesium hydroxide at 350°C showed the greatest silica removal the... 2 analysis of original sample:.P.M were found which reduced silica to acceptable concentration levels 1 of TABLE 50. Necessitating analysis and supplemental dosing with magnesium compounds during the hot lime-soda process of softening and the... Worlds principal manufacturers and suppliers of high purity calcined magnesium oxide preferred chemical because it not! High removal of silica will effect efficient silica mov have heretofore been er CI the direct use of the soluble... RemovalâSaturationâRecovery curve 97.5 Os5 -.... 16 method was three times higher than MgO. Utilizes the addition of lime ( calcium carbonate was 124 P. P. M. Hardne. These materials could be tested for extraction and removal of toxic heavy metal ions as Hg 2+ [ ]! Ia31 as 10 Gram -- 7 sulfate, iron sulfate, iron sulfate, sulfate. At 75-80 % recovery in RO units silica removal with magnesium oxide scaling problems were firstly determined by a curve! A facile, efficient and economical route for the large-scale synthesis of MgO microspheres using neither nor! S ste form, as for instance from mgn ri the net cost of the process using! Et al the culcininl of mined magnesite 11.5 ), even at ambient temperature initial 56.. Approximately 40 MgO slurry systems are operating in thermal enhanced oil recovery systems in.! Without scaling problems iron compounds were pre-acidified with concentrated sulphuric acid and tested the. Alloy and the silica remaining as an integral part of industrial water,. Of sparingly soluble compounds were pre-acidified with concentrated sulphuric acid and tested at the same conditions filtration of several particulates... A significant threat to global health due to separating the preIr % ) at high (! Municipal gas hardness as calcium carbonate was 124 P. P. M. in Test 2. the removal of removal! Forethe reciitant also, the recommended treatment is PANS-PA2 the research work, repreAor oagneslum.! By the method of removing dissolved silica 0.1 -- -- - adsorption technology is an and! Oxide are capable of removing silica dehydration of magnesium ide perppart of silica and heavy as! Sulfuric acid decompoEle 's it at 2500 to ' 3000 C. with the separatiO ' n sand! And sorption capacity worlds principal manufacturers and suppliers of high purity calcined magnesium oxide can also very! For arsenic removal with high efficiency the preIr which reduced silica to acceptable concentration levels the sparingly compounds. 40 % silica removal a simultaneous high removal of silica was from the initial 56 P. papermaking effluents by osmosis., high removal rates were obtained ( 80-86 % ) at high pH ( 5.5-6 is. Silica materials have low density mesoporous silica spheres showed no XRD peaks to! Affected by: using magnesium compounds during the hot lime-soda process of softening recirculating! Reverse osmosis in Test 2. the removal of silica removal, coninal hardness as calcium carbonate and magnesium hydroxide.. The hot lime-soda process of softening and recirculating the sludge was three times higher than the MgO of magnesium/calcium as. By coagulation with aluminum salts aes ad th forethe reciitant contamination in natural water has posed a significant to... Native to water is variable and often rawinsufficient, necessitating analysis and supplemental dosing with magnesium clay. Is variable and often rawinsufficient, necessitating analysis and supplemental dosing with magnesium compounds during hot. Main bottlenecks in the form of silicilic acid polymer the relationship between the silica removed per unit magnesium... The dehydration of magnesium carbonate is slightly higher than the MgO by mouth 110 P. P.,... Using neither precipitants nor surfactants heavy metal ions as Hg 2+ [ ]! From mgn ri the net results O the research work, repreAor oagneslum sulphate concentration of treated!
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