Polyaluminum chloride prepared from coal gangue by microwave hydrothermal method and method thereof

Abstract

The invention relates to a method for preparing polyaluminum chloride from coal gangue by a microwave hydrothermal method. The raw materials consist of the following materials: 1-5g of coal gangue; 3-15 ml of 20% hydrochloric acid; the invention also discloses the preparation method which comprises the following steps: S1, crushing the coal gangue; s2, calcining and activating the coal gangue; s3, cooling; s4, mixing the materials; s5, microwave acid leaching; s6, filtering; s7, drying and weighing filter residues; s8, polymerizing and curing the filtrate; and S9, evaporating and crystallizing the sedimentation liquid. The method has the advantages that the polyaluminum chloride prepared from the coal gangue is easy in raw material obtaining and simple in process, the inorganic polymeric flocculant with high added value is prepared by properly processing the coal gangue, and compared with other acid leaching methods, the microwave method has the advantages that the acid leaching time is shortened from 1-3 h to 15 min, the solid-to-liquid ratio is reduced from 1: (3.5-7) to 1: 3, the cost is saved, the energy consumption is reduced, and the prepared product PAC can reduce the turbidity of domestic sewage of 24.740 NTU to 8.761 NTU, and the water purification effect is remarkable.

Description

technical field [0001] The invention belongs to the application technical field of coal gangue, and in particular relates to a method for preparing polyaluminum chloride by microwave hydrothermal method using coal gangue as a raw material. Background technique [0002] Coal gangue is solid waste discharged during the coal mining process and coal washing process. It is a black-gray rock with low carbon content and harder than coal that is associated with coal seams during the coal formation process. Its main component is Al 2 o 3 , SiO 2 , also contains varying amounts of Fe 2 o 3 , CaO, MgO, Na 2 O, K 2 O.P 2 o 5 , SO 3 And trace rare elements (gallium, vanadium, titanium, cobalt). [0003] So far, the use of coal gangue has not been strong enough. The technology is not perfect, the regional development is unbalanced, and the impact on the environment is still very serious, mainly in the following aspects: (1) affecting the utilization of land resources; (2) pollu...

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Problems solved by technology

[0006] The preparation technology of polyaluminum chloride prepared from coal gangue is recorded in Chinese patent documents, for example: Chinese patent CN106277008A utilizes gel method to prepare polyaluminum chloride, coal gangue is activated at 700°C for 8h, and 20% hydrochloric acid is leached at 90°C for 2h , the solid-liquid ratio is 1:40, after microfiltration, add sodium hydroxide to adjust the pH, hydrolyze at 30°C for 3 hours to obtain polyaluminum chloride gel, and vacuum freeze-dry to obtain powder. The disadvantage is that the activation time is too long and the consumption of hydrochloric acid is too large. The prepared polyaluminum chloride has a low turbidity removal rate

[0007] In Chinese patent CN108408858A, coal gangue and sulfuric acid slag are used as raw materials, acid leached at 105°C for 3.5 hours, polymerized at 98°C for 4 hours, and aged at room temperature for 24 hours to obtain polyaluminum ferric chloride. All indicators of the obtained product meet the national standard, but the product preparation cycle long, complicated process

[0008] Chinese patent CN107473353A uses sodium hydroxide, coal gangue and pyrite slag to be activated together at 1150°C for 1.5h. The activator is mixed with 25% hydrochloric acid at a ratio of 1:7, acid leached at 106°C for 3h, and then heated at 37°C Under aging for 36 hours to obtain polyaluminum ferric chloride, this method increases the leaching rate of aluminum oxide in coal gangue, but the activation temperature is too high, the consumption of acid and alkali in the preparation process also increases, and the concentration of hydrochloric acid reaches 25%. too long

[0009] In summary, the current method of preparing polyaluminum chloride from coal gangue is acid leaching, but the time of acid leaching, acid concentration and dosage, reaction and aging time, etc., lead to a preparation cycle ranging from 7 hours to 3 days

In addition, the traditional hydrothermal and water bath methods mainly increase the extraction rate of aluminum in coal gangue by increasing the reaction time, and the investment in energy consumption is relatively large.

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