Phosphate Adsorption onto Granular-Acid-Activated-Neutralized Red Mud: Parameter Optimization, Kinetics, Isotherms, and Mechanism Analysis

Abstract

Powdered-acid-activated-neutralized red mud (Aan-RM), the chemico-physically modified product of red mud, was for the first time employed with hydroxypropyl methylcellulose and powdered straw as the main ingredients for granular Aan-RM production for phosphate removal. In order to better understand the phosphate adsorption characteristics of granular Aan-RM, the influence of operational parameters on the performance of granular Aan-RM and the possible adsorption mechanisms involved were investigated. The results demonstrated that the adsorbent dosage, adsorption temperature, and initial solution pH influenced the adsorption performance of granular Aan-RM significantly. The maximum phosphate adsorption capacity of granular Aan-RM reached 153.227 mg/g with the granular Aan-RM dosage of 3.0 g/L, adsorption temperature of 40°C, and initial solution pH of 6.0. The whole adsorption process was well described by nth-order kinetic model and Langmuir-Freundlich isotherm. Meanwhile, X-ray photoelectron spectroscopy (XPS) analysis of P 2p peak on granular Aan-RM after phosphate adsorption demonstrated that 79.01 % of the phosphate was adsorbed through precipitation and ion exchange mechanisms with strong chemical bonds, and 20.99 % of the phosphate was adsorbed through surface deposition mechanism with weak chemical bonds.

Granulation of Cobalt-containing Nickel Hydroxide with Polyethylene Terephthalate and its Phosphate Ion Adsorption Capability

“…The highest phosphate ion adsorption capacities of 9.0, 12.0, and 15.0 mg/g for PET20L, PET20M, and PET20S, respectively, were observed at pH 6.0 − 7.0. Previous studies reported similar trends [3,20,22,39,55]. At pH lower than 2.16, phosphorus mainly existed in the form of H 3 PO 4 .…”

“…At lower pH, the phosphate ion adsorption performance would be restricted, since H 3 PO 4 is not active in ion exchange with hydroxyl groups on the PET20 surface. In contrast, at higher pH, the competition between OH − and the phosphate ion adsorption was strong, indicated by a decreased amount of adsorbed phosphate with increasing solution pH [3,56].…”

“…Therefore, much effort has been devoted to the development of various new techniques to reduce and control the phosphate concentration in wastewater [3][4][5][6][7]. The techniques for aqueous phosphate removal include chemical precipitation, crystallization, adsorption, and biological processes with denitrifying phosphateaccumulating organisms [8][9][10][11][12][13][14].…”

“…The techniques for aqueous phosphate removal include chemical precipitation, crystallization, adsorption, and biological processes with denitrifying phosphateaccumulating organisms [8][9][10][11][12][13][14]. Among these techniques, the adsorption method is considered to be superior to other techniques for water reuse in terms of cost, simplicity of design, ease of operation, and insensitivity to toxic substances [3,15,16]. A variety of adsorbents have been developed for phosphate removal [17][18][19].…”

Separation-free Al-Mg/graphene oxide composites for enhancement of urban stormwater runoff quality

“…Similar variations of the C=C peak were also observed in the ATR-FTIR spectra of DCF-laden composites due to π-π interactions. Specifically, delocalized π electrons with sp 2 carbon grains interacted with the free electrons in the aromatic rings of DCF [23,64,66]. In addition, oxygen-containing groups are available to form the hydrogen bonds with amino-group of DCF molecules.…”