Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review

Abstract

Geopolymers, as a kind of inorganic polymer, possess excellent properties and have been broadly studied for the stabilization/solidification (S/S) of hazardous pollutants. Even though many reviews about geopolymers have been published, the summary of geopolymer-based S/S for various contaminants has not been well conducted. Therefore, the S/S of hazardous pollutants using geopolymers are comprehensively summarized in this review. Geopolymer-based S/S of typical cations, including Pb, Zn, Cd, Cs, Cu, Sr, Ni, etc., were involved and elucidated. The S/S mechanisms for cationic heavy metals were concluded, mainly including physical encapsulation, sorption, precipitation, and bonding with a silicate structure. In addition, compared to cationic ions, geopolymers have a poor immobilization ability on anions due to the repulsive effect between them, presenting a high leaching percentage. However, some anions, such as Se or As oxyanions, have been proved to exist in geopolymers through electrostatic interaction, which provides a direction to enhance the geopolymer-based S/S for anions. Besides, few reports about geopolymer-based S/S of organic pollutants have been published. Furthermore, the adsorbents of geopolymer-based composites designed and studied for the removal of hazardous pollutants from aqueous conditions are also briefly discussed. On the whole, this review will offer insights into geopolymer-based S/S technology. Furthermore, the challenges to geopolymer-based S/S technology outlined in this work are expected to be of direct relevance to the focus of future research.

Immobilization Approach as a Creative Strategy to Remove Reactive Dye Red 195 and Cu2+ Ions from Wastewater Using Environmentally Benign Geopolymer Cement

“…An inorganic polymer known as a geopolymer is made up of SiO 4 and AlO 4 tetrahedrons that are joined by exchanging oxygen atoms [ 17 ]. They can usually be created by low-temperature polycondensation of silica- and alumina-rich raw materials’ natural and byproducts, such as metakaolin, blast furnace slag, coal fly ash, and red mud [ 17 , 18 , 19 ]. Geopolymers may be essentially described as a three-dimensional, amorphous, or semicrystalline aluminosilicate framework.…”

“…Geopolymers may be essentially described as a three-dimensional, amorphous, or semicrystalline aluminosilicate framework. It has been regarded as a workable substitute for Portland cement due to its superior mechanical characteristics, durability, low energy requirements, and low greenhouse gas emissions [ 17 ]. In addition, geopolymers have gained a lot of attention recently, particularly in wastewater treatment for the removal of various organic and inorganic pollutants including heavy metals and dyes [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], using a variety of methods, primarily adsorption as well as photodegradation, encapsulation, and immobilization [ 17 , 28 , 29 , 30 , 31 , 32 ].…”

“…As geopolymers offer so many promising attributes as a cement substitute material in terms of financial, environmental, and technological advantages, a sizable body of literature has been devoted to their potential for usage in the building sector. Geopolymers have increasingly garnered a lot of attention for the immobilization of harmful wastes in recent years [ 17 ]. For the Solidification/Stablization of hazardous pollutants, which are classified into heavy metals (cations and anions) and organic pollutants, geopolymers are currently the topic of extensive several studies [ 17 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ].…”

Entrapment of Acridine Orange in Metakaolin-Based Geopolymer: A Feasibility Study

“…One of the peculiar chemical properties of these geopolymers is the capability to encapsulate additional cations and anions through the stabilization/solidification process [ 7 , 8 ] and even macromolecules [ 9 , 10 , 11 , 12 ] remaining entrapped during the aluminosilicate 3D network, which presents crypto-zeolite local organization [ 13 ]. Because of the presence of zeolite A in the formulations of geopolymers based on Brazilian metakaolins [ 14 ], the consolidated geopolymers displayed high adsorption capacity within short times (between one and five minutes) for different cationic dyes, i.e., methylene blue, safranin, and malachite green from aqueous solutions.…”

Synthesis of a Magnetic Carnation-like Hydroxyapatite/Basic Calcium Carbonate Nanocomposite and Its Adsorption Behaviors for Lead Ions in Water

“…The treatment of wastewater polluted by heavy metal ions has become one of the most onerous challenges for the sustainable development of human society because of their detrimental effects on the environment and human health [ 1 , 2 , 3 , 4 ]. As one of the major heavy metals in the natural environment, lead (Pb) is considered a serious threat to the ecological environment and human health due to its high toxicity and persistent characteristics [ 5 ].…”