How to utilize the waste liquid from the preparation of ZSM-5 molecular sieves
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The waste liquid resulting from the preparation of ZSM-5 molecular sieves using water glass and alkalis contains large amounts of aluminate ions; how can this waste be recycled? Thank you
When dilute hydrochloric acid is added, a reaction takes place that produces an aluminum hydroxide precipitate: NaAlO2 + HCl + H2O = Al(OH)3↓ + NaCl. The precipitate is washed with water and then filtered, allowing aluminum hydroxide to be recovered. Be careful not to use an excessive amount of hydrochloric acid; if too much is used, AlCl3 will be formed and the precipitate will disappear. NaAlO2+HCl----NACl+ALCl3; theoretically, it is as shown above. If recycling is to be carried out, you need to consider whether there is a cheap source of dilute hydrochloric acid, as well as the cost of investing in recycling equipment, the operating expenses, and the price of recycled aluminum hydroxide, to determine whether it is economical.
When preparing ZSM-5 molecular sieves, the utilization rate of Al is relatively high. Generally, SI in the filtrate is recycled.