WO2021036391A1 - 一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法 - Google Patents

一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法 Download PDF

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WO2021036391A1
WO2021036391A1 PCT/CN2020/094390 CN2020094390W WO2021036391A1 WO 2021036391 A1 WO2021036391 A1 WO 2021036391A1 CN 2020094390 W CN2020094390 W CN 2020094390W WO 2021036391 A1 WO2021036391 A1 WO 2021036391A1
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impurities
adsorbent
humate
oxalate
bayer
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PCT/CN2020/094390
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English (en)
French (fr)
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皮溅清
赵志强
王明理
黄桂华
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杭州科创有色金属研究有限公司
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Publication of WO2021036391A1 publication Critical patent/WO2021036391A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0646—Separation of the insoluble residue, e.g. of red mud

Definitions

  • the invention relates to the technical field of alumina preparation, in particular to a method for removing humate and oxalate impurities in Bayer liquor.
  • the general method for preparing alumina from bauxite is the Bayer process; specifically, the Bayer process uses a high-concentration sodium hydroxide circulating solution to dissolve bauxite under high temperature and high pressure conditions. A nearly saturated sodium aluminate solution is obtained, and then aluminum hydroxide seed crystals are added, and aluminum hydroxide is obtained by precipitation.
  • Bauxite contains more or less organic impurities. These organic impurities will enter the liquid phase together with the alumina in the ore during the dissolution process, contaminating the sodium aluminate solution. Most of the organics in bauxite are long-chain high-molecular-weight organic compounds, such as humates. Among them, some long-chain organics are degraded into short-chain organics during the dissolution process, resulting in a series of dissolution in lye Of organic salts.
  • the humate organic matter is composed of colored compounds, so the Bayer liquor is red or dark red; in addition, the lye in the process of producing alumina by the Bayer process is recycled, which leads to continuous organic matter in the Bayer liquor. accumulation.
  • the specific hazards include the color of Bayer liquid, which affects the whiteness of the product aluminum hydroxide; the increase in the viscosity of Bayer liquid, the production system is prone to foam; and the increase of the solubility of oxalate organics in Bayer liquid will cause oxalic acid in Bayer liquid.
  • the decomposition yield decreases; when the oxalate reaches a certain concentration, it will co-crystallize with aluminum hydroxide in the decomposition process, causing the decomposition tank to scar, the aluminum hydroxide filtration efficiency decreases, the product is refined, and the alkali attachment increases Wait.
  • the above-mentioned hazards seriously affect the normal production of the alumina industry, so measures need to be taken to control the content of this type of organic matter.
  • the methods currently used in industry include (1) crystallization in the mother liquor by evaporation. Control the concentration and temperature of the evaporation mother liquor, and add oxalate seed crystals to make oxalate crystallize and separate. (2) Wash the fine aluminum hydroxide seeds, and add lime to the oxalate-rich lotion for causticization. (3) Adding additives to the decomposition process to form spherical oxalate crystals, and then separate the grown spherical oxalate crystals.
  • the industrially applied methods include (1) the liquid combustion method in which aluminum hydroxide is added to the evaporated Bayer liquor and then calcined at a high temperature to remove the organic impurities in the Bayer liquor. (2) Control the discharge of alkali from the red mud, so that part of the long-chain organic matter is discharged with the red mud. (3) Plants with sintering method use the sintering method to high-temperature calcination to remove. (4) Wet oxidation method, by adding oxygen (or oxide) to the high-temperature dissolution device to degrade long-chain organic matter into short-chain organic or inorganic matter.
  • the experimental studies carried out include (1) adding magnesium-containing compounds to Bayer liquor to generate a mixed precipitate of magnesium hydroxide and aluminum hydroxide to remove part of the organic impurities in the Bayer liquor; (2) adding barium-containing compounds to Bayer liquor The compound produced by the precipitation of barium aluminate contains organic impurities adsorbed from Bayer liquor; (3) A cation chelating agent is added to Bayer liquor, and the cation chelating agent can interact with the humic acid in Bayer liquor. The salt produces a poorly soluble product, and the sodium oxalate in the Bayer liquor becomes unstable and precipitates. (4) Activated carbon is added to the Bayer liquor, and the activated carbon is used to adsorb humate.
  • the above methods either have obvious difficulties in specific operations, or are too costly in the actual application process to be industrially applied.
  • the purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for simultaneously removing humate and oxalate impurities in Bayer liquor.
  • a method for removing the impurities of humate and oxalate in Bayer liquor includes adding industrial adsorbent to Bayer liquor, and after stirring uniformly, adsorbing humate impurities, and forming adsorbent after the precipitation of oxalate impurities, The mixture of humate impurities and oxalate impurities can be separated into solid and liquid.
  • the adsorbent is a solid industrial adsorbent with a particle size of 10-75 ⁇ m, a specific surface area of 230-350 m 2 /g and insoluble in water, and the added amount of the adsorbent is 2-20 g/L.
  • the adsorbent used in the present invention is a cheap and readily available solid particulate adsorbent that is insoluble in water and can adsorb humate impurities.
  • the humate impurities in the Bayer liquor are destroyed at the same time.
  • the balance of humate and oxalate makes the oxalate impurities precipitate and form a mixture of adsorbent, humate impurities and oxalate impurities, and at the same time can speed up the bursting speed of the foam in Bayer liquid.
  • the Bayer liquor is an alkali-containing liquid of the Bayer process for producing alumina after being concentrated and free of solid impurities, and the caustic concentration of the Bayer liquor is 180-250g in Na 2 O terms. /L.
  • the temperature of the Bayer liquid is 55-68°C.
  • reaction time for the precipitation of the oxalate impurity is greater than 120 minutes.
  • the adsorbent is an industrial by-product of activated carbon.
  • the content of humate impurities in the Bayer liquor is 0.10-1.00 g/L.
  • the content of the oxalate impurity in the Bayer solution is 1.50-2.50 g/L.
  • the stirring time after the adsorbent is added to the Bayer liquid is 8-12 min.
  • the stirring speed of the adsorbent after being added to the Bayer liquid is 50-80 rpm.
  • the method for removing humate and oxalate impurities in the Bayer liquor further includes adding a filter aid during the solid-liquid separation process.
  • the method for removing humate and oxalate impurities in Bayer liquor includes the following steps:
  • the mixed slurry containing the mixture of adsorbent, humate impurities and oxalate impurities is introduced into a plate and frame filter press and then filtered.
  • the method for removing humate and oxalate impurities in Bayer liquor can use common industrial adsorbents to directly adsorb and remove humates in Bayer liquor, and at the same time promote the instability of oxalate in Bayer liquor. It precipitates and is removed by precipitation together with the adsorbent, and also has the function of eliminating Bayer liquid foam; compared with the existing physical adsorption method, the adsorbent used in the present invention is cheap and easy to obtain.
  • the mixture of adsorbent, humate impurity and oxalate impurity formed by the adsorbent used in the present invention is easy to separate liquid and solid, and a plate filter press commonly used in industry can be used to complete adsorbent, humate impurity and The separation of oxalate impurity mixture is more feasible for industrial application than the physical adsorption method in the prior art, and its processing cost is lower.
  • the adsorbent, humate impurity and oxalate impurity mixture are obtained after the separation of adsorbent, humate impurity and oxalate impurity mixture.
  • the filtrate can be recycled again and used in the Bayer process to prepare alumina, which is beneficial to the comprehensive utilization of resources and environmental protection, has a wide range of application prospects, and is of great practical significance.
  • the invention realizes industrial application and has received good technical and economic effects.
  • the Bayer liquid refers to all alkali-containing liquids produced by the Bayer process; typically including dissolution liquid, diluent, semen, mother liquid (decomposition mother liquid, flat plate mother liquid), evaporation mother liquid, etc.
  • concentration of alkali in the liquid is different, and all contain organic impurities.
  • the above-mentioned organic impurities refer to the organic substances dissolved in Bayer liquid, and their quantity and type are closely related to the bauxite used and the operating conditions of the factory; most of the organic impurities are in the form of organic sodium, except for rot Except for carboxylate, they are basically colorless.
  • the substances that can cause the solution to darken are mainly humic acid substances.
  • the composition of these substances is not fixed and the structure is complex. For the sake of simplicity, all colored organic substances present in Bayer liquid are called "humates".
  • the humate in Bayer liquid will not only cause aluminum hydroxide to be colored, but also increase the viscosity of Bayer liquid and cause the system to foam; increase the stability of the sodium aluminate solution in Bayer liquid and reduce the decomposition yield; It can be used as a stabilizer for other dissolved organic impurities, such as oxalate impurities.
  • humate organics extracted from bauxite can cause the existence of most low-molecular-weight organic substances.
  • the stabilizing effect of humate can make the concentration of low-molecular-weight organic matter in Bayer liquor exceed its supersaturation; the precipitation produced by these low-molecular-weight organic impurities is difficult to control, especially oxalate with very fine particle size. It will precipitate together with aluminum hydroxide in the decomposition stage, which will seriously affect the quality of the product aluminum hydroxide.
  • the purpose of this method is to control the content of humate organic matter and oxalate in Bayer liquor; what is used is to treat concentrated humic acid and oxalate with a cheap industrial adsorbent under certain conditions Bayer fluid.
  • the concentrated solution refers to the Bayer liquor after the low-concentration mother liquor is concentrated by evaporation; the concentrated Bayer liquor has suitable temperature and alkalinity, which is conducive to the efficient removal of humic acid and oxalate from the liquid by the adsorbent, and Liquid-solid separation in the later stage.
  • the process of the method used in the embodiment of the present invention is briefly described as follows.
  • the Bayer liquor after evaporation and concentration, calculated as Na 2 O, with a caustic concentration of 200-220 g/L) is introduced into a mixer, and 2 is added to it at the same time.
  • -20g/L adsorbent, the adsorbent and Bayer liquid are fully mixed in the mixer until there is no dry adsorbent floating on the surface of the Bayer liquid.
  • the mixing process can be completed in about 10 minutes; then, the mixture is uniformly mixed.
  • the slurry is sent to a large conical reaction tank. The volume of the reaction tank should ensure that the slurry stays in it for more than 2 hours.
  • the bottom of the reaction tank should be equipped with a low-speed stirring rake to prevent solids from sinking;
  • the slurry is discharged from the bottom and sent to the plate and frame filter press.
  • the Bayer liquor treated with organic matter is returned to the process again. It contains adsorbents, humates, oxalates and some
  • the filter cake mixture with Bayer liquid is transported to other processes for use, which completes the removal of organic impurities.
  • the removal rate of humic acid is about 29%; as the amount of adsorbent added increases (about 10g/L), the removal rate of humic acid increases. As large as about 50%.
  • the removal rate of oxalate has little to do with the amount of adsorbent added.
  • the amount of adsorbent added ranges from 2-15 g/L, and the removal rate of oxalate in Bayer liquor is about 50%.
  • This comparative example provides a method for removing humate and oxalate impurities in Bayer liquor.
  • the specific process is similar to the embodiment, except that the industrial adsorbent (particle size is 10-75 ⁇ m, specific surface area is 230- The addition amount of 350m 2 /g) is 10g/L, but the temperature of the Bayer solution is 78°C, and the caustic alkali concentration ( calculated as Na 2 O) is 150g/L.
  • the absorbance of the filtrate after pressure filtration is also measured, and the result of calculating the removal rate of humate is 44%; and the content of oxalate in the filtrate after pressure filtration is measured, the result of calculating the removal rate of oxalate is 21.5 %.
  • present invention further illustrates the method of the present invention with industrial production examples, which are specifically as follows:
  • the removal rate of humic acid is 41.12%, and the removal rate of oxalate is about 59%.
  • the bubble burst time for 300ml of the original solution is 330s, and the bubble burst time for the 300ml Bayer solution treated with the adsorbent is 110s, which is only 1/3 of the original time.
  • the invention provides a method for simultaneously removing humate and oxalate impurities in Bayer liquor.
  • the method provided by the present invention includes: adding an adsorbent to Bayer liquor, absorbing humate impurities after stirring uniformly, and forming an adsorbent, a mixture of humate impurities and oxalate impurities after the oxalate impurities are precipitated, solid-liquid
  • the separation is sufficient; wherein, the adsorbent is a solid adsorbent with a particle size of 10-75 ⁇ m, a specific surface area of 230-350 m 2 /g, and is insoluble in water, and the added amount of the adsorbent is 2-20 g/L.
  • the method of the present invention can use industrial adsorbents to directly adsorb and remove humates and promote the instability of oxalate precipitation, co-precipitation and removal; compared with the existing physical adsorption method, the adsorbent of the present invention is an industrial by-product, which is economical and easy Obtained; lower operating costs, and is conducive to the comprehensive utilization of resources and environmental protection, has good economic value and application prospects, practical significance.

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Abstract

本发明公开了一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法，包括，向拜耳液中加入吸附剂，搅拌均匀后吸附腐殖酸盐杂质，待草酸盐杂质析出后形成吸附剂、腐殖酸盐杂质和草酸盐杂质混合物，固液分离即可；其中，所述吸附剂为粒径为10-75μm、比表面积为230-350m 2/g且不溶于水的固体吸附剂，所述吸附剂的加入量为2-20g/L。本发明的方法可采用工业吸附剂直接吸附去除腐殖酸盐并促进草酸盐失稳析出，共同沉淀而被去除；与现有物理吸附法相比，本发明的吸附剂经济易得；其工业化应用可行性更强，运行成本低，能有利于资源的综合利用和环境保护，具有很好的应用前景，实际意义重大。

Description

一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法
交叉引用
本申请要求2019年8月30日提交的专利名称为“一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法”的第201910814566.0号中国专利申请的优先权，其全部公开内容通过引用整体并入本文。
技术领域
本发明涉及氧化铝制备技术领域，具体涉及一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法。
背景技术
现有技术中，从铝土矿中制备氧化铝的通用办法是拜耳法；具体地，拜耳法是采用高浓度的氢氧化钠循环溶液，在高温高压条件下溶出铝土矿，铝土矿溶出得到接近饱和的铝酸钠溶液，然后再加入氢氧化铝晶种，通过沉淀法得到氢氧化铝。
世界上不同产地铝土矿的成份是不同的。铝土矿中或多或少的含有有机杂质，这些有机杂质在溶出过程中会和矿石中的氧化铝一起进入液相，污染铝酸钠溶液。铝土矿中的大部分有机物是长链的高分子量有机化合物，如腐殖酸盐类，其中，部分长链有机物在溶出过程中降解为短链有机物，从而产生了一系列溶解于碱液中的有机盐类。其中，腐殖酸盐类有机物是由有颜色的化合物组成，因此拜耳液呈红色或暗红色；此外，拜耳法生产氧化铝过程中的碱液是循环使用的，这就导致拜耳液中有机物不断累积。当拜耳液中的有机物累积到较高的浓度，会产生一系列的危害。其危害具体包括，拜耳液带色，影响产品氢氧化铝的白度；拜耳液粘度增大，生产系统易产生泡沫；增大草酸盐类有机物在拜耳液中的溶解度，引起拜耳液中草酸盐平衡浓度升高，分解产出率降低；草酸盐达到一定浓度后将在分解环节与氢氧化铝共结晶，造成分解槽结疤，氢氧化铝过滤效率下降，产品细化，附碱上升等。上述危害严重地影响氧化铝工业的正常生产， 因此需采取措施控制这类有机物的含量。
使用有机杂质含量高的矿石作为原料，采用拜耳法生产氧化铝过程中，拜耳液中有机杂质的控制是非常重要的，因此，各国学者开展了一系列控制拜耳液中有机杂质的研究，具体可分为两个方面的工作，一方面是控制系统草酸盐浓度，另一方面是控制系统非草酸盐类长链有机物的浓度。
在控制系统草酸盐浓度方面，目前得以工业应用的方法有(1)蒸发母液中结晶析出。控制蒸发母液的浓度、温度，并添加草酸盐晶种，使草酸盐结晶析出并分离。(2)对氢氧化铝细种子进行洗涤，将富集草酸盐的洗液加石灰苛化。(3)向分解工序添加助剂，形成球状草酸盐结晶，再分离长大的球状草酸盐结晶。
在控制系统非草酸盐类长链有机物的浓度方面，得以工业应用的方法有(1)液体燃烧法，蒸发后的拜耳液添加氢氧化铝，然后经高温煅烧以除去拜耳液中的有机杂质。(2)控制赤泥外排附碱，让一部分长链有机物隨赤泥排出。(3)有烧结法的工厂借助烧结法高温煅烧来去除。(4)湿法氧化法，通过向高温溶出装置中加入氧气(或氧化物)使长链的有机物降解为短链的有机物或无机物。
开展的试验研究包括(1)在拜耳液中加入含镁的化合物，生成氢氧化镁和氢氧化铝的混合沉淀，以除去拜耳液中的部分有机杂质；(2)在拜耳液中加入含钡的化合物，生成铝酸钡沉淀，该沉淀中含有从拜耳液中吸附出的有机杂质；(3)向拜耳液中加入一种阳离子螯合剂，该阳离子螯合剂可以和拜耳液中的腐殖酸盐生产一种难溶的产物，同时拜耳液中的草酸钠失稳而析出。(4)向拜耳液中加入活性炭，用活性炭吸附腐殖酸盐。以上方法要么在具体操作上有明显的困难，要么是在实际应用过程中成本太大，难以产业化应用。
发明内容
本发明的目的是克服现有技术的不足，提供一种同时去除拜耳液中腐 殖酸盐和草酸盐杂质的方法。
本发明采用如下技术方案：
一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法，包括，向拜耳液中加入工业吸附剂，搅拌均匀后吸附腐殖酸盐杂质，待草酸盐杂质析出后形成吸附剂、腐殖酸盐杂质和草酸盐杂质混合物，固液分离即可。
其中，所述吸附剂为粒径为10-75μm、比表面积为230-350m 2/g且不溶于水的固体工业吸附剂，所述吸附剂的加入量为2-20g/L。
具体地，本发明所使用的吸附剂为廉价易得的不溶于水且能吸附腐殖酸盐杂质的固体颗粒状吸附剂，通过吸附拜耳液中的腐殖酸盐杂质，同时破坏拜耳液中的腐殖酸盐和草酸盐的平衡，使草酸盐杂质析出并形成吸附剂、腐殖酸盐杂质和草酸盐杂质混合物，同时还能加快拜耳液中泡沫的破灭速度。
在上述技术方案中，所述拜耳液为经浓缩后且不含固体杂质的拜耳法生产氧化铝过程的含碱液体，且以Na 2O计，所述拜耳液的苛碱浓度为180-250g/L。
进一步地，在上述技术方案中，所述拜耳液的温度为55-68℃。
在上述技术方案中，所述草酸盐杂质析出的反应时间大于120min。
进一步地，在上述技术方案中，所述吸附剂为活性炭类工业副产品。
再进一步地，在上述技术方案中，所述拜耳液中腐殖酸盐杂质的含量为0.10-1.00g/L。
优选地，在上述技术方案中，所述拜耳液中草酸盐杂质的含量为1.50-2.50g/L。
还进一步地，在上述技术方案中，所述吸附剂加入到拜耳液后的搅拌时间为8-12min。
还进一步地，在上述技术方案中，所述吸附剂加入到拜耳液后的搅拌转速为50-80rpm。
还进一步地，在上述技术方案中，所述去除拜耳液中腐殖酸盐和草 酸盐杂质的方法还包括，在所述固液分离过程中加入助滤剂。
在一个优选实施例中，所述去除拜耳液中腐殖酸盐和草酸盐杂质的方法，包括以下步骤：
S1、将以Na 2O计，苛碱浓度为200-220g/L的蒸发拜耳液引入混料器中，同时按2-20g/L的比例加入粒径为10-75μm、比表面积为230-350m 2/g的吸附剂，60-75rpm下搅拌8-12min得到混合料浆；
S2、将混合料浆引入底部带搅拌器的锥形反应槽中，20-30rpm下搅拌，析出反应120-150min，得到含吸附剂、腐殖酸盐杂质和草酸盐杂质混合物的混合料浆；
S3、将含吸附剂、腐殖酸盐杂质和草酸盐杂质混合物的混合料浆引入板框压滤机中压滤即可。
本发明具有如下优点：
本发明所提供的去除拜耳液中腐殖酸盐和草酸盐杂质的方法可采用常用的工业吸附剂直接吸附去除拜耳液中的腐殖酸盐，同时促进拜耳液中的草酸盐失稳析出，并随吸附剂一同沉淀而被去除，而且还兼具消除拜耳液泡沫的作用；与现有物理吸附法相比，本发明所采用的吸附剂廉价易得。
本发明所采用的吸附剂形成的吸附剂、腐殖酸盐杂质和草酸盐杂质混合物易于液固分离，可采用工业上常用的板式压滤机即能完成吸附剂、腐殖酸盐杂质和草酸盐杂质混合物的分离，与现有技术的物理吸附法相比其工业化应用可行性更强，且其处理成本更低，吸附剂、腐殖酸盐杂质和草酸盐杂质混合物分离后得到的滤液可再次循环回收用于拜耳法制备氧化铝，有利于资源的综合利用和环境保护，具有广泛的应用前景，实际意义重大。
本发明实现了工业化应用，收到了很好的技术、经济效果。
具体实施方式
下面结合具体实施例，对本发明的具体实施方式作进一步详细描述。以下实例用于说明本发明，但不用来限制本发明的保护范围，本发明的保 护范围以权利要求书为准。
若未特别指明，本发明实施例中所用的实验试剂和材料等均可市售获得；若未具体指明，本发明实施例中所用的技术手段均为本领域技术人员所熟知的常规手段。
本发明实施例中所用原料来源：
在本发明实施例中，所述拜耳液指的是拜耳法生产中所有的含碱液体；典型的包括溶出液、稀释液、精液、母液(分解母液、平盘母液)、蒸发母液等，这些液体中碱浓度不同，而且都含有有机杂质。
上述有机杂质指的是溶解于拜耳液中的有机物质，其数量和类别与所用铝土矿和工厂的操作条件有很大关系；大部分的有机杂质是以有机酸钠的形式存在，除了腐殖酸盐外，基本都是无色的。能引起溶液颜色变深的物质，主要是腐殖酸盐类物质，这类物质的组成不是固定的，且结构复杂。为了简单起见，把拜耳液中存在的所有有色有机物质都叫做“腐殖酸盐”。拜耳液中的腐殖酸盐不仅会引起氢氧化铝带色，还会增加拜耳液的粘度，使系统起泡；增加拜耳液中铝酸钠溶液的稳定性，降低分解产出率；同时还可作为其他溶解的有机杂质的稳定剂，例如草酸盐杂质。
实际上，我们通常认为，从铝土矿中提取的腐殖酸盐类有机物可以导致大多数低分子量有机物物质的存在。腐殖酸盐的这种稳定作用可以使得拜耳液中的低分子量有机物质浓度超过其过饱和度；这些低分子量的有机杂质生产的沉淀难以控制，尤其是粒度很细的草酸盐，可以在分解阶段和氢氧化铝一起析出，这会严重的影响产品氢氧化铝的质量。例如，若草酸盐在氢氧化铝表面析出，需要大量的水才能将氢氧化铝洗干净；析出的草酸盐会促进氢氧化铝晶核的形成，致使生产的氢氧化铝粒度过细。若草酸盐夹杂在氢氧化铝晶格中，在焙烧过程中，氢氧化铝会爆裂开来，就会得到粒度不合格的氧化铝；同时不受控制的草酸盐沉淀，会使容器结垢严重，影响槽罐的使用周期，还需要额外的劳动力去清理结疤。因此，要想经济而有效的生产出合格的氢氧化铝，控制系统拜耳液中的腐殖酸盐和草酸盐 类有机物物质是很有必要的。
本方法的目的就是控制拜耳液中腐殖酸盐类有机物和草酸盐的含量；所采用的是在一定条件下用一种廉价的工业吸附剂处理浓缩后的含有腐殖酸和草酸盐的拜耳液。该浓缩液指的是低浓度的母液经过蒸发浓缩后的拜耳液；此浓缩的拜耳液温度和碱度适宜，利于吸附剂高效的脱除液体中的腐殖酸，草酸盐的析出，以及后期的液固分离。
本发明实施例所采用方法的流程简述如下，将蒸发浓缩后的拜耳液，以Na 2O计，其苛碱浓度为200-220g/L)引入一个混料器中，同时向其中加入2-20g/L的吸附剂，吸附剂和拜耳液在混料器中充分混合，直到没有干的吸附剂漂浮在拜耳液表面为止，此混合过程大约在10min左右可完成；然后，将混合均匀的料浆送入一个大的锥形反应槽中，该反应槽的体积应保证料浆在其中停留2h以上，该反应槽底部应带有低速的搅拌耙机，以防固体沉死；最后，从底部放出料浆，送入板框压滤机中，经板框压滤机液固分离后，处理过有机物的拜耳液重新返回流程中，含有吸附剂、腐殖酸盐、草酸盐以及一些附带拜耳液的滤饼混合物运送至其它工序利用，即完成了整个有机物杂质的去除工作。
实施例
分别按2-15g/L的加入量，往苛碱浓度(以Na 2O计)为210g/L的拜耳液(温度为60℃)中加入活性炭吸附剂(粒径为10-75μm、比表面积为230-350m 2/g)，在混料器中充分混合10min；然后，将混合均匀的料浆送入锥形反应槽中，缓慢搅拌(25rpm)反应2h；最后，从底部放出料浆，送入板框压滤机中压滤。
测定压滤后的滤液的吸光度，计算腐殖酸盐的去除率，具体结果如下表1所示。
表1腐殖酸盐去除率与吸附剂加入量的变化关系
Figure PCTCN2020094390-appb-000001
注：吸附剂和拜耳液反应完成后，将料浆用滤纸过滤，对滤液进行吸光度测定。用1厘米比色杯和721G/721G-100可见分光光度计在575nm出测量吸光度。
如表1的结果可知，当吸附剂加入量为2g/L时，腐殖酸的去除率为29％左右；随着吸附剂加入量的增多(10g/L左右)，腐殖酸去除率增大到50％左右。
测定压滤后的滤液的草酸根的含量，计算草酸盐的去除率，具体结果如下表2所示。
表2草酸盐去除率与吸附剂加入量的变化关系
Figure PCTCN2020094390-appb-000002
注：吸附剂和拜耳液反应完成后，将料浆用滤纸过滤，对滤液中草酸根含量进行测定。所用仪器为Thermo ICS-600离子色谱仪。
如表2的结果可知，草酸盐的去除率与吸附剂的加入量关系不大，吸附剂的加入量从2-15g/L，拜耳液中草酸盐的去除率均在50％左右。
此外，还测定了不同吸附剂的加入量与拜耳液的消泡效果的关系，具体结果如下表3所示。
表3拜耳液消泡效果与吸附剂加入量的变化关系
Figure PCTCN2020094390-appb-000003
如表3的结果可知，在量筒中加入一定量的拜耳液，然后向其中鼓入气体，这时量筒中会有气泡产生。因起泡速度大于气泡破灭的速度，所以量筒内的气泡会不断增多。当气泡量到达300ml时，停止鼓气，这时气泡会逐渐破灭。未用吸附剂处理的拜耳液，300ml气泡破灭用时300秒。用2g/L的吸附剂处理过的拜耳液，同样体积的气泡破灭用时180秒，破灭速度加快。随着吸附剂加入量的增多，气泡破灭的速度大大加快，当加入量为5g/L以上时，气泡破灭用时仅为原来的1/3；综上可知，加入适量吸附剂对生产稳定具有明显益处。
对比例
本对比例提供了一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法，具体工艺过程与实施例类似，区别在于，工业吸附剂(粒径为10-75μm、比表面积为230-350m 2/g)的加入量为10g/L，但其拜耳液的温度为78℃，苛碱浓度(以Na 2O计)为150g/L。
反应完成后，同样测定压滤后的滤液的吸光度，计算腐殖酸盐去除率的结果为44％；并测定压滤后的滤液的草酸根的含量，计算草酸盐去除率的结果为21.5％。
此外，本发明还以工业生产实例对本发明的方法做了进一步说明，具体如下：
将拜耳液送至混合槽中，然后打开混合槽搅拌，将吸附剂按6～7g/L缓慢的加入反应槽中，吸附剂全部加入后，在搅拌的作用下，拜耳液和吸附剂混合均匀；然后，由泵打入锥形反应槽中，静置2h以上；之后打开锥形反应槽的放料阀，料浆进入压滤机的饲料槽中，打开压滤机进料泵，压滤得到的拜耳液送回流程中；当进料压力升至0.6～0.7Mp后，停泵，关闭压滤机进料阀，之后卸下滤饼。
将拜耳液和收集的处理后滤液进行分析，具体结果如下表4所示。
表4拜耳液和处理后滤液的分析结果
Figure PCTCN2020094390-appb-000004
如表4的结果可知，腐殖酸的去除率为41.12％，草酸根去除率为59％左右。原液300ml泡沫破灭的时间为330s，用吸附剂处理后的拜耳液300ml的泡沫破灭的时间为110s，用时只为原来的1/3。
最后，上文中已经用一般性说明及具体实施方案对本发明作了详尽的描述，但在本发明基础上，可以对之作一些修改或改进，这对本领域技术人员而言是显而易见的。因此，在不偏离本发明精神的基础上所做的这些修改或改进，均属于本发明要求保护的范围。
工业实用性
本发明提供一种同时去除拜耳液中腐殖酸盐和草酸盐杂质的方法。本发明提供的方法包括：向拜耳液中加入吸附剂，搅拌均匀后吸附腐殖酸盐杂质，待草酸盐杂质析出后形成吸附剂、腐殖酸盐杂质和草酸盐杂质混合 物，固液分离即可；其中，所述吸附剂为粒径为10-75μm、比表面积为230-350m 2/g且不溶于水的固体吸附剂，所述吸附剂的加入量为2-20g/L。本发明的方法可采用工业吸附剂直接吸附去除腐殖酸盐并促进草酸盐失稳析出，共同沉淀而被去除；与现有物理吸附法相比，本发明的吸附剂为工业副产品，经济易得；运行成本更低，且有利于资源的综合利用和环境保护，具有很好的经济价值和应用前景，实际意义重大。

Claims (10)

  1. 一种去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，包括，向拜耳液中加入吸附剂吸附腐殖酸盐杂质，并使草酸盐杂质失稳，待草酸盐杂质析出后形成吸附剂、腐殖酸盐杂质和草酸盐杂质混合物，固液分离即可；
    其中，所述吸附剂为粒径为10-75μm、比表面积为230-350m 2/g且不溶于水的固体吸附剂，所述吸附剂的加入量为2-20g/L。
  2. 根据权利要求1所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述拜耳液为经浓缩后且不含固体杂质的拜耳法生产氧化铝过程的含碱液体，且以Na 2O计，所述拜耳液的苛碱浓度为180-250g/L。
  3. 根据权利要求1或2所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述拜耳液的温度为55-68℃。
  4. 根据权利要求1所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述草酸盐杂质析出的反应时间大于120min。
  5. 根据权利要求1-4任一项所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述吸附剂为活性炭类工业吸附剂。
  6. 根据权利要求1-5任一项所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述拜耳液中腐殖酸盐杂质的含量为0.10-1.00g/L。
  7. 根据权利要求6所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，所述拜耳液中草酸盐杂质的含量为1.50-2.50g/L。
  8. 根据权利要求1-7任一项所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，
    所述吸附剂加入到拜耳液后的搅拌时间为8-12min；
    和/或，所述吸附剂加入到拜耳液后的搅拌转速为50-120rpm。
  9. 根据权利要求1-7任一项所述的去除拜耳液中腐殖酸盐和草酸盐 杂质的方法，其特征在于，还包括，在所述固液分离过程中加入助滤剂。
  10. 根据权利要求1-9任一项所述的去除拜耳液中腐殖酸盐和草酸盐杂质的方法，其特征在于，包括以下步骤：
    S1、将以Na 2O计，苛碱浓度为200-220g/L的蒸发拜耳液引入混料器中，同时按2-20g/L的比例加入粒径为10-75μm、比表面积为230-350m 2/g的吸附剂，60-75rpm下搅拌8-12min得到混合料浆；
    S2、将混合料浆引入底部带搅拌器的锥形反应槽中，20-30rpm下搅拌，析出反应120-150min，得到含吸附剂、腐殖酸盐杂质和草酸盐杂质混合物的混合料浆；
    S3、将含吸附剂、腐殖酸盐杂质和草酸盐杂质混合物的混合料浆引入板框压滤机中压滤即可。
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