SU865812A1

SU865812A1 - Method of regerating spent chromium-containing solutions

Info

Publication number: SU865812A1
Application number: SU792847397A
Authority: SU
Inventors: Сергей Сергеевич Афонский; Галина Никитична Новицкая; Елена Сергеевна Губская; Софья Борисовна Лепская; Николай Яковлевич Киреев; Лидия Захаровна Изотова
Original assignee: Институт общей и неорганической химии АН УССР; Московский автомобильный завод им.И.А.Лихачева
Priority date: 1979-12-06
Filing date: 1979-12-06
Publication date: 1981-09-23

Description

Изобретение относится к машиностроению и может быть использовано в металлообработке при пассивировании и травлении металлов рации отработанных в процессах регенехромсодержащих ра створов.The invention relates to mechanical engineering and can be used in metalworking when passivating and etching metals of the radio used in regenerated chromium-containing solutions.

Известны способы переработки и ре генерации хромсодержащих растворов, основанные на предварительном восстановлении соединений шестивалентного хрома до трехвалентного состояния с помощью различных восстановителей и последующей переработке трехвалентного хрома на различные соединения, например сульфаты, хлориды или гидро- 15 окись хрома [1] и [2].Known methods for the processing and regeneration of chromium-containing solutions are based on the preliminary reduction of hexavalent chromium compounds to a trivalent state using various reducing agents and the subsequent processing of trivalent chromium into various compounds, for example, sulfates, chlorides, or chromium hydroxide [1] and [2].

Недостатками этих способов являются расход восстановителей, а также трудность получения чистых готовых продуктов из-за наличия в отработан- 20 ных растворах примес.ей других металлов .The disadvantages of these methods are the consumption of reducing agents, as well as the difficulty of obtaining pure finished products due to the presence of impurities from other metals in the spent 20 solutions.

Наиболее близким к изобретению по технической сущности и достигаемому результату является способ регенера- 25 ции растворов для хроматирования цинка и кадмия, заключающийся в том, что в отработанный раствор сначала вводят NaOH до pH 5-9, затем флокулянт (полиакриламид), а после осаждения и 30 отделения ионов Zn^z и Cd²⁺фильтрованием в фильтрат добавляют HrjSO^ до рабочих значений pH и вводят раствор соединения шестивалентного хрома хромат натрия.The closest to the invention in terms of technical nature and the achieved result is a method for the regeneration of solutions for the chromation of zinc and cadmium 25, which consists in the fact that NaOH is introduced into the spent solution to pH 5-9, then flocculant (polyacrylamide), and after precipitation and To separate the Zn ^z and Cd ^{2+ ions by} filtration, HrjSO ^ is added to the filtrate to the working pH and a solution of hexavalent chromium sodium chromate compound is added.

В отработанном растворе протекают следующие реакции:The following reactions proceed in the spent solution:

ZnCr₂0₇+ 4NaOH -+Zu (0Н)₂ + 2Na СгОд+ Η_χ0,;(») CdCr₂O₇+ 4 Na ОН -> Cd ( ОН )_г + 2Na^CrO4+ Н₂0;(2) Сг_г(Сг_гО₇),+ 12NaOH -?2Cr(0H)₃ + 6Na₂CrQj + + зн_го; (3)ZnCr ₂ 0 ₇ + 4NaOH - + Zu (0Н) ₂ + 2Na СГОд + Η _χ 0,; (») CdCr ₂ O ₇ + 4 Na ОН -> Cd (ОН) _g + 2Na ^ CrO4 + Н ₂ 0; (2 ) _{g of} Cr (Cr _z O _7), + 12NaOH - 2Cr (0H ) ₃ + 6Na ₂ CrQj + + receptacle _g of?; (3)

N ajCi^ + 2 Нз5 04-^2 N33504+ Н_гСг_гО₇ + Н₂0;(4) ^Н2?^г2°1 ^{+ 2N0}2^Cr04^ ²Na₂Cr₂O₇ + Н^0. (5)N ajCi ^ + 2 Нз5 04- ^ 2 N33504 + Н _г Сг _г О ₇ + Н ₂ 0; (4) ^Н 2? ^g 2 ° 1 ^{+ 2N0} 2 ^Cr0 4 ^ ² Na ₂ Cr ₂ O ₇ + Н ^ 0. (5)

Однако в рабочих растворах постепенно накапливается сульфат натрия, который не являетсянеобходимым компонентом раствора, а при больших избытках его необходимо удалять, т.е. серная кислота расходуется непроизводительно .However, sodium sulfate, which is not an essential component of the solution, gradually accumulates in working solutions, and with large excesses it must be removed, i.e. sulfuric acid is consumed unproductive.

Таким образом, корректировка раствора по величине pH и концентрации основного компонента Na^Cr^O-j осуществляется двумя реактивами: и Na Cr₂0₇. Кроме того, расходуется флокулянт - полиакриламид, а стадия образования осадка продолжается 1,5-2 ч.Thus, the solution is adjusted for pH and the concentration of the main component Na ^ Cr ^ Oj by two reagents: and Na Cr ₂ 0 ₇ . In addition, a flocculant - polyacrylamide is consumed, and the stage of sedimentation lasts 1.5-2 hours.

Цель изобретения - упрощение процесса регенерации раствора, уменьше3 ние расхода реагентов и сокращение времени образования осадка.The purpose of the invention is to simplify the process of regeneration of the solution, reducing the consumption of reagents and reducing the time of sedimentation.

Поставленная цель достигается тем, что отработанные растворы предварительно нагревают до 40-50°С, а в качестве соединения шестивалентного хрома вводят хромовый ангидрид в ко1ичестве, эквивалентном щелочи.This goal is achieved by the fact that the spent solutions are preheated to 40-50 ° C, and chromic anhydride is introduced in an amount equivalent to alkali as a hexavalent chromium compound.

Предварительный подогрев отработанного раствора способствует лучшей коагуляции осадка без применения специального коагулянта и уменьшает расход реагента (NaOH) за счет снижения pH гидратообразования осадка примесей. Благодаря своим кислотным свойствам хромовый ангидрид позволяет подкислить раствор до рабочей величины pH, а также откорректировать его по бихромат-ионам.Preheating the spent solution promotes better coagulation of the precipitate without the use of a special coagulant and reduces the consumption of reagent (NaOH) by lowering the pH of hydrate formation of the precipitate of impurities. Due to its acidic properties, chromic anhydride allows you to acidify the solution to a working pH, as well as adjust it for dichromate ions.

Реакции (1) - (3) протекают аналогично известному способу, а вместо реакций (4) и (5) протекает реакцияReactions (1) - (3) proceed similarly to the known method, and instead of reactions (4) and (5), the reaction proceeds

N ajC гОд+ CrO-j-^N а₂С г₂ 0 ₇ , (6 ) что значительно упрощает процесс регенерации и не приводит к образованию в регенерирующих растворах побочного продукта - Na_aS0₄. Кроме того, реакции (4) и (5) сопровождаются выделением Н₂0 , что приводит к разбавлению рабочих растворов, а при действии твердого Сг₂.0з образование воды в системе исключается.N ajC gOd + CrO-j- ^ N a ₂ C g ₂ 0 ₇ , (6) which greatly simplifies the regeneration process and does not lead to the formation of a by-product in the regenerating solutions - Na _a S0 ₄ . In addition, reactions (4) and (5) are accompanied by the release of H ₂ 0, which leads to dilution of the working solutions, and under the action of solid Cr ₂ .0z the formation of water in the system is excluded.

Перед добавлением осадителя (NaOH) отработанный раствор предварительно нагревают до 40-50°С, что исключает необходимость введения флокулянта и снижает количество добавляемого реагента за счет снижения pH осаждения примесей.Before the addition of precipitant (NaOH), the spent solution is preheated to 40-50 ° C, which eliminates the need for the introduction of a flocculant and reduces the amount of added reagent by reducing the pH of the deposition of impurities.

Нейтральную соль, необходимую для корректировки раствора, вводят в виде двух образующих ее компонентов (основного и кислотного характера) с промежуточным осаждением и отделением осадка примесей металлов, причем при введении последнего происходит подкисление раствора до требуемой величины pH и одновременно его корректировка по бихромат-ионам.The neutral salt necessary for adjusting the solution is introduced in the form of two components forming it (basic and acidic) with intermediate precipitation and separation of the precipitate of metal impurities, and when the latter is introduced, the solution is acidified to the required pH and simultaneously corrected for dichromate ions.

Рост температуры от 20 до 50°С уменьшает количество NaOH в 3 раза и сокращает время осаждения осадка от 1,5 ч до 5 мин при одинаковой степени очистки отработанного раствора пассивирования цинка состава, г/л; Na₂Cr₂ 0₇ 50 ; Zn^z4 3 и С г³⁴ 1,5. При осаждении меди из отработанного раствора пассивирования меди состава, г/л: Na₂Cr₂O₇ 100 и Си²⁴ 3, повышений температуры от 22 до 50 С также способствует уменьшению количества осадителя (NaOH) в 3,5 раза и сокращению времени осаждения осадка от 1-2 ч до 10-15 мин для достижения примерно равной величины pH гидратообразования осадка - 5,9-5,7.An increase in temperature from 20 to 50 ° C reduces the amount of NaOH by 3 times and reduces the precipitation time of the precipitate from 1.5 hours to 5 minutes with the same degree of purification of the spent zinc passivation solution, g / l; Na ₂ Cr ₂ 0 ₇ 50; Zn ^z4 3 and C g ³⁴ 1.5. When copper is precipitated from a spent passivation solution of copper with a composition, g / l: Na ₂ Cr ₂ O ₇ 100 and Cu ²⁴ 3, temperature increases from 22 to 50 C also contribute to a decrease in the amount of precipitant (NaOH) by 3.5 times and a reduction in the deposition time sediment from 1-2 hours to 10-15 minutes to achieve approximately equal pH of hydrate formation of sediment - 5.9-5.7.

Пример!. 1 отработанного раствора пассивирования цинка^, содержащий, г/л: NaaCraO, 45, Zn 3 иExample!. 1 spent zinc passivation solution ^, containing, g / l: NaaCraO, 45, Zn 3 and

С г 1,5, нагревают до 5 0°С и вводят в него 1,6 кг NaOH. При этом величина pH возрастает от 2,5 до 5,7, а образовавшийся осадок примесей полностью коагулирует в течение 5 мин. После отделения осадка в очищенный раствор добавляют 2,0 кг твердого СгО^, величина pH при этом снижается .до 1,5, что является рабочей для данного раствора и одновременно происходит корректировка раствора, по бихромату натрия, увеличивая общую концентрацию Na₂Cr₂O₇ в растворе приблизительно на 5 г/л,' _а With g of 1.5, it is heated to 5 ° C and 1.6 kg of NaOH are introduced into it. In this case, the pH increases from 2.5 to 5.7, and the resulting precipitate of impurities completely coagulates within 5 minutes. After separation of the precipitate, 2.0 kg of solid CrO ^ is added to the purified solution, the pH value decreases. To 1.5, which is working for this solution and at the same time the solution is adjusted according to sodium dichromate, increasing the total concentration of Na ₂ Cr ₂ O ₇ in solution at about 5 g / l, _a

П р и м е р 2. 1м^- отработанного раствора пассивации меди, содержащий г/л: Na_aCr₂ 0₇ 180 / Си⁹·⁴ 3 и Сг³⁺ 2, нагревают до 45°С и вводят в него 5 кг NaOH, При этом величина pH возрастает от 1,6 до 5.,2, а образовавшийся осадок примесей полностью коагулирует в течение 10 мин.PRI me R 2. 1 m ^- waste passivation solution of copper containing g / l: Na _a Cr ₂ 0 ₇ 180 / Cu ⁹ · ⁴ 3 and Cr ³⁺ 2, heated to 45 ° C and injected into it 5 kg NaOH, In this case, the pH increases from 1.6 to 5., 2, and the resulting precipitate of impurities completely coagulates for 10 minutes.

После отделения осадка в очищенный раствор добавляют 12 кг твердого СгО_э, величина pH при этом снижается до 1,6, что является рабочей для данного раствора, и одновременно происходит корректировка раствора по бихромату натрия.After separating the precipitate, 12 kg of solid CrO _e are added to the purified solution, the pH value being reduced to 1.6, which is working for this solution, and at the same time the solution is adjusted for sodium dichromate.

ПримерЗ. 1м’ отработанного раствора хроматирования цинка и кадмия, содержащий, г/л: Na„ С г 0 100;Example 3. 1 m ’of an exhausted solution of chromation of zinc and cadmium, containing, g / l: Na„ С g 0 100;

Cd⁷⁴ 3,0 и Zn²⁴ 4, нагревают до 42°С и вводят в него 3,2 кг NaOH. При этом величина pH возрастает от 2,1 до 7, а образовавшийся осадок примесей полностью коагулирует в течение 15 мин. После отделения осадка в очищенный раствор добавляют 8 кг твердого С г0_э, величина pH при этом снижается до 1,5, что является рабочей для данного раствора, и одновременно происходит корректировка раствора по бихромату натрия.Cd ⁷⁴ 3.0 and Zn ²⁴ 4, heated to 42 ° C and introduced into it 3.2 kg of NaOH. In this case, the pH increases from 2.1 to 7, and the resulting precipitate of impurities completely coagulates for 15 minutes. After separation of the precipitate, 8 kg of solid C g _Oe is added to the purified solution, the pH value being reduced to 1.5, which is working for this solution, and at the same time the solution is adjusted for sodium dichromate.

Технико-экономическое преимущество предлагаемого способа по сравнению с известным заключается в возможности осуществления многократного использования отработанных растворов', так как они не загрязняются Na^SO^; в упрощении способа регенерации за счет исключения дополнительных стадий обработки, а также в сокращении расхода реагентов и уменьшение времени обработки, так как сокращается одна иэ самых длительных стадий процесса регенерации - образование осадка после введения щелочи - с 1-2 ч до 5-15 мин.The technical and economic advantage of the proposed method compared to the known one consists in the possibility of reusing the used solutions', since they are not contaminated with Na ^ SO ^; in simplifying the regeneration method by eliminating additional processing stages, as well as in reducing the consumption of reagents and reducing the processing time, since one of the longest stages of the regeneration process — the formation of a precipitate after the introduction of alkali — is reduced from 1-2 hours to 5-15 minutes.

Claims

The invention relates to mechanical engineering and can be used in metal processing during passivation and etching of metals in the processes of regeneration of waste chrome-containing solutions. There are known methods for processing and generating chromium-containing solutions based on preliminary reduction of compounds of hexavalent chromium to the trivalent state using various reducing agents and subsequent processing of trivalent chromium into various compounds, for example, sulfates, chlorides or chromium hydroxide 1 and

2. The disadvantages of these methods are the consumption of reducing agents, as well as the difficulty of obtaining pure finished products due to the presence of impurities of other metals in the spent solutions. The closest to the invention in its technical essence and the achieved result is the method of regeneration of solutions for chromate zinc and cadmium, which consists in the fact that firstly NaOH is added to pH 5-9, then flocculant polyacrylamide), and after precipitation Separating the Zn and Cd ions by filtration is added to the filtrate to the working pH values and a solution of a hexavalent chromium sodium chromate compound is added. The following reactions proceed in the spent solution: 4NaOH (OH) 2 + 2 g CdCr2 0 -, + 4NaOH - Cd (OH) 2. + g04 + NgODZ} С2. (СГ2.0,), + 12NaOH -92Сг (ОН) g + + + 3H, j, 0; f 2Na2Cr04 + + HgO;) + 2NO, CrO, + 0. (f However, sodium sulfate gradually accumulates in the working solutions, which is not a necessary component of the solution, and with large excess it must be removed i.e. sulfuric acid is consumed unproductively. Thus, the adjustment of the solution according to the pH value and concentration of the main component is carried out with two reagents: and NaCr-O. In addition, flocculant is consumed polyacrylamide, and the stage of sludge formation lasts 1.5-2 hours. The purpose of the invention is to simplify the process of solution regeneration, reduce the consumption of reagents and reduce the time of sludge formation. The goal is achieved by the fact that the spent solutions are previously n-heated to 4 ° -50 ° C , and chromic anhydride is introduced as a hexavalent chromium compound in a quantity equivalent to alkali. Preheating the spent solution helps to better coagulate the precipitate without using a special coagulant and reduces the consumption of the reagent (NaOH) by lowering the pH of the precipitate hydrate forming the impurities. Due to its acidic properties, chromic anhydride allows acidifying the solution to the working pH value, as well as adjusting it with bichromate ions. Reactions (1) - (3) proceed in a manner similar to the known method, and instead of reactions (4) and (5), the reaction proceeds М2СгОд + CrO, -, (6) which greatly simplifies the regeneration process and does not lead to the formation of a by-product in the regenerating solutions - N a. In addition, reactions (4) and (5) are accompanied by separation, which leads to the dilution of working solutions, and under the action of solid CrO2. Water is eliminated in the system. Before adding the precipitant (NaOH, the spent solution is preheated to 40–50 ° C, which eliminates the need for flocculating and reduces the amount of added reagent by lowering the pH of precipitating impurities. Neutral salt needed to adjust the solution is introduced as two of the constituent components (basic and acidic) with intermediate precipitation and separation of the sediment of metal impurities, and with the introduction of the latter, the solution is acidified to the required pH and at the same time its correction Dichromate ion formation: The temperature rises from 20 to 3 times the amount of NaOH and reduces the sedimentation time of the precipitate by about 1.5 hours to 5 minutes with the same degree of purification of the spent zinc passivation solution, g / l; Na.Cr, jO , 50; Zn 3 and C g 1.5. When copper is deposited from a spent copper passivation solution of composition, g / l: Na2., 100 and Cu 3, a temperature increase from 22 to 50 ° C also contributes to a decrease in the amount of precipitator (NaOH) in 3.5 times and the reduction {of the precipitation precipitation time from 1-2 h to 10-15 min to achieve approximately equal to the pH of the hydrate forming and sediment - 5,9-5,7. Example. A 1m waste solution of passivation of zinc, containing g / l: NaaCfiOiij 45, Zn 3 and C g 1.5, is heated to 50 ° C and 1.6 kg of NaOH are introduced into it. At the same time, the pH value increases from 2.5 to 5.7, and the precipitate of impurities formed completely coagulates within 5 minutes. After separating the precipitate, 2, O kg of solid CrO are added to the purified solution, the pH value is reduced to 1.5, which is working for this solution, and at the same time the solution is corrected for sodium bichromate, increasing the total concentration of Na. about 5 g / l in solution. 1m of spent copper passivation solution, containing g / l: Ma CgzO-, 180; 3 and Cr 2, is heated before and 5 kg of NaOH is introduced into it. The pH value increases from 1.6 to 5.2., And the precipitate of impurities formed completely coagulates within 10 minutes. After separating the precipitate, 12 kg of solid CgO3 is added to the purified solution, the pH value decreases to 1.6, which is working for this solution, and at the same time the sodium bichromate solution is adjusted. Example 3. 1m of a spent chromate solution of zinc and cadmium, containing, g / l: Na g 100 100; 3.0 and Zn 4 are heated to 42 ° C and 3.2 kg of NaOH are introduced into it. At the same time, the pH value increases from 2.1 to 7, and the resulting precipitate of impurities coagulates completely within 15 minutes. After separating the precipitate, 8 kg of solid CgOe is added to the purified solution, the pH value is reduced to 1.5, which is working for this solution, and at the same time the sodium bichromate solution is adjusted. The technical and economic advantage of the proposed method in comparison with the known one is the possibility of multi-use of the used solutions, since they are not polluted,. in simplifying the regeneration method by eliminating additional processing steps, as well as reducing reagent consumption and reducing processing time, as one of the longest stages of the regeneration process is reduced — wasp formation, after the introduction of alkali, from 1-2 hours to 5 15 minutes. Claims of the regeneration method: spent chromium-containing solutions, which include treating with alkali with NaOH to a pH of 5.9, separating the precipitate formed by filtration, introducing a compound of hexavalent cream into the mixture, and 8658126

Compared with the fact that, with the aim of Sources of information, simplification of the method, reduction of consumption, taken into account in the examination of reagents and reduction of the time of formation of a precipitate, waste solutions. USSR author's certificate preheated to 40-50s, No. 424816, cl. C 01 G 37/00, 1972. and chromic anhydride, M 533675, Cl, C 23 G 1/36, 1975, is used as a hexavalent-2 compound of the USSR Chrome's Copyright Certificate, in an amount equivalent to

3. Patent of Great Britain No. 1538656, choi alkali, cl, C 1 C, 1976.