Study On Preparation Of Layered Crystalline Sodium Disilicate From Silica-rich Filtrate And Its Application To Detergent Auxiliary

This paper is a part of the subject of the national "Eleventh Five-Year" science and technology support projects in "insoluble potassium and mineral resources utilization".Project team take Shaanxi luonan potassium feldspar as raw material,after grinding,sintering,flooding,filtering aluminum residue to get rich in sodium silicate, partial potassium silicate flooding of the filtrate.This study experiment set flooding filtrate as raw material to prepare layered crystalline sodium disilicate.Layered crystalline sodium disilicates（Na₂Si₂O₅）have good ion binding capacity,fine alkaline buffer capacity,co-operation with other composition in good method,harmony with environment and so on.They were considered as efficient non-pHospHate detergent builder with excellent prospect.Firstly,flooding filtrate was acidified with carbon dioxide,the solution is changed from sol to gel.The silica particle are growed and aggregated and through washing and filtration,after filtration,silica gel separated from sodium carbonate.We use a modest distilled water washed the silica gel three times,then washed it once with dilute hydrochloric acid to remove the potassium silicate and a small amount of colloidal impurities（iron hydroxide,aluminum hydroxide）.Pure silica gel was obtained.The Layered crystalline sodium disilicate was prepared with this rich silica gel and caustic soda,a certain ratio,through low-temperature drying,calcinations.By orthogonal and single factor experiments,we can prepare the layered crystalline sodium disilicate with the best effect.To products,X-ray diffraction analysis,calcium and magnesium ion exchange capacity as the main test index.The optimum condition of preparation:sodium silicate modulus is 1.0,drying temperature is 120℃,drying time is 1.5h,calcination temperature is 750℃,calcinations time is 1.5h.Under optimum conditions,Products meet the national standard of layered crystalline sodium disilicate.As detergent auxiliary,layered crystalline sodium disilicate and sodium carbonate,sodium sulfate,fatty alcohol polyoxyethylene ether,sodium dodecyl benzene sulfonate,Sodium carboxymethyl cellulose,mixed together to form a washing powder.During single factor experiment,the optimal washing condition were determined:the concentration of 0.6%detergent,wash before soaking for 20min,washing temperature of 35℃,washing time was 30min,bath ratio of 100:1, wash water hardness of about 200mg/L.Layered crystalline sodium disilicate and other detergent auxiliary such as 4A zeolite,sodium tripolypHospHate,under the same conditions match,do wash detergency contrast test,the results show that the layered crystalline sodium disilicate washing decontamination capacity is better than others.