Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red

Xingpeng Wang; Chao Jiang; Huiyu Li; Weiliang Tian; Saeed Ahmed; Yongjun Feng

doi:10.3390/ma17092034

Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red

Materials (Basel). 2024 Apr 26;17(9):2034. doi: 10.3390/ma17092034.

Authors

Xingpeng Wang¹, Chao Jiang¹, Huiyu Li¹, Weiliang Tian², Saeed Ahmed³, Yongjun Feng^{1

2

4}

Affiliations

¹ State Key Laboratory of Chemical Resource Engineering, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, China.
² College of Chemistry and Chemical Engineering, Tarim University, Alar 843300, China.
³ Department of Chemistry, University of Chakwal, Chakwal 48800, Pakistan.
⁴ Gansu West Attapulgite Application Research Institute, Baiyin 730900, China.

Abstract

Attapulgite (APT) is widely used in wastewater treatment due to its exceptional adsorption and colloidal properties, as well as its cost-effectiveness and eco-friendliness. However, low-grade APT generally limits its performance. Here, a colloid mill-assisted ultrasonic-fractional centrifugal purification method was developed to refine low-grade APT. This process successfully separated and removed impurity minerals such as quartz and dolomite from the raw ore, resulting in a refined APT purity increase from 16.9% to 60% with a specific surface area of 135.5 m²∙g^-1. Further modifying of the refined APT was carried out through the hydrothermal method using varying dosages of cetyltrimethylammonium chloride (CTAC), resulting in the production of four different APT adsorbents denoted as QAPT-n (n = CTAC mole number) ranging from 0.5 to 5 mmol. Using Congo red (CR) as the target pollutant, the QAPT-5 sample exhibited the best adsorption capacity with the maximum quantity of 1652.2 mg∙g^-1 in a neutral solution at 30 °C due to the highest surface charge (zeta potential = 8.25 mV). Moreover, the QAPT-5 pellets (~2.0 g adsorbent) shaped by the alginate-assisted molding method removed more than 96% of 200 mL aqueous solution containing 200 mg∙L^-1 CR and maintained this efficiency in 10 adsorption-elution cycles, which exhibited the promising practical application.

Keywords: Congo red; attapulgite; colloid mill; modification; purification.

Grants and funding

This research was funded by Gansu Cuihua Technology Co., Ltd. (H2020292), Science and Technology Planning of Baiyin City, Fundamental Research Funds for the Central Universities (buctrc202208), the Engineering Research Center of Non-metallic Minerals of Zhejiang Province and the Beijing Engineering Center for Hierarchical Catalysts, The Central Government Guiding Funds for Local Science and Technology Development (2022ZY015), Nanjiang Technology Project (2023AB028), and the Open Laboratory of the State Key Laboratory of Organic and Inorganic Composites (oic-202301006).