Preparation of a novel magnetic geopolymer/zero–valent iron composite with remarkable adsorption performance towards aqueous Acid Red 97

Behaviors and Mechanisms of Adsorption of MB and Cr(VI) by Geopolymer Microspheres under Single and Binary Systems

Geopolymers show great potential in complex wastewater treatment to improve water quality. In this work, general geopolymers, porous geopolymers and geopolymer microspheres were prepared by the suspension curing method using three solid waste products, coal gangue, fly ash and blast furnace slag. The microstructure, morphology and surface functional groups of the geopolymers were studied by SEM, XRD, XRF, MIP, FTIR and XPS. It was found that the geopolymers possess good adsorption capacities for both organic and inorganic pollutants. With methylene blue and potassium dichromate as the representative pollutants, in order to obtain the best removal rate, the effects of the adsorbent type, dosage of adsorbent, concentration of methylene blue and potassium dichromate and pH on the adsorption process were studied in detail. The results showed that the adsorption efficiency of the geopolymers for methylene blue and potassium dichromate was in the order of general geopolymers < porous geopolymers < geopolymer microspheres, and the removal rates were up to 94.56% and 79.46%, respectively. Additionally, the competitive adsorption of methylene blue and potassium dichromate in a binary system was also studied. The mechanism study showed that the adsorption of methylene blue was mainly through pore diffusion, hydrogen bond formation and electrostatic adsorption, and the adsorption of potassium dichromate was mainly through pore diffusion and redox reaction. These findings demonstrate the potential of geopolymer microspheres in adsorbing organic and inorganic pollutants, and, through five cycles of experiments, it is demonstrated that MGP exhibits excellent recyclability.

Zinc (Ⅱ) functionalized magnetic geopolymer as sorbents for rapid extraction of Fluoroquinolones in food prior to quantification by UHPLC-MS/MS

A novel Zn@MGeo sorbent was easily constructed and can bind with FQs through the synergistic effect of electrostatic interaction and coordination. With the Zn@MGeo as sorbent, a MSPE-UHPLC-MS/MS method was established for simultaneous detection of FQs in complex matrices. The whole extraction process could be completed using 6.0 mg sorbent within 10 min under the optimal conditions. The established quantitative method obtained a wide linear range (0.01-200 μg/kg, R² > 0.9987), high sensitivity (LODs: 0.005-0.05 μg/kg) and negligible matrix effect. The method was applied for analysis of real samples, with recoveries between 75.6% and 103.7%. In addition, the sorbent could be reused at least 9 times without reducing the adsorption performance. In general, the established method not only proposes a novel sorbent for FQs extraction, but also provides a powerful tool for rapid and sensitive detection of FQs in food matrices with practical application value.

A comprehensive review on sustainable clay-based geopolymers for wastewater treatment: circular economy and future outlook

In the present era of significant industrial development, the presence and dispersal of countless water contaminants in water bodies worldwide have rendered them unsuitable for various forms of life. Recently, the awareness of environmental sustainability for wastewater treatment has increased rapidly in quest of meeting the global water demand. Despite numerous conventional adsorbents on deck, exploring low-cost and efficient adsorbents is interesting. Clays and clays-based geopolymers are intensively used as natural, alternative, and promising adsorbents to meet the goals for combating climate change and providing low carbon, heat, and power. In this narrative work, the present review highlights the persistence of some inorganic/organic water pollutants in aquatic bodies. Moreover, it comprehensively summarizes the advancement in the strategies associated with synthesizing clays and their based geopolymers, characterization techniques, and applications in water treatment. Furthermore, the critical challenges, opportunities, and future prospective regarding the circular economy are additionally outlined. This review expounded on the ongoing research studies for leveraging these eco-friendly materials to address water decontamination. The adsorption mechanisms of clays-based geopolymers are successfully presented. Therefore, the present review is believed to deepen insights into wastewater treatment using clays and clays-based geopolymers as a groundbreaking aspect in accord with the waste-to-wealth concept toward broader sustainable development goals.

Novel modeling and optimization framework for Navy Blue adsorption onto eco-friendly magnetic geopolymer composite

The disproportionate potency of dyes in textile wastewater is a global concern that needs to be contended. The present study comprehensively investigates the adsorption of Navy-Blue dye (NB) onto bentonite clay based geopolymer/Fe₃O₄ nanocomposite (GFC) using novel statistical and machine learning frameworks in the following steps; (1) synthesis and characterization of GFC, (2) experimental testing and modelling of NB adsorption onto GFC following Box-Behnken design and three response surface prediction models namely stepwise regression analysis (SRA), Support vector regression (SVR) and Kriging (KR), (3) parametric, sensitivity, thermodynamic and kinetic analysis of pH, GFC dose and contact time on adsorption performance, and (4) finding global parametric solution of the process using Latin Hypercube, Sobol and Taguchi orthogonal array sampling and combining SRA-SVR-KR predictions with novel hybrid simulated annealing (SA)-desirability function (DF) approach. Under the given testing range, parametric/sensitivity analysis revealed the critical role of pH over others accounting ∼37% relative effect and primarily derived the NB adsorption. The statistical evaluation of models revealed that all models could be utilized for elucidating and predicting the NB removal using GFC, however, SVR accuracy was better among others for this particular work, as the overall computed root mean squared error was only 0.55 while the error frequency counts remained <1 for 90% predictions. GFC showed 86.29% NB removal for the given experimental matrix which can be elevated to 96.25% under optimum conditions. The NB adsorption was found to be physical, spontaneous, favorable and obeyed pseudo-2nd order kinetics. The results demonstrate the suitability of GFC as the promising cost-effective and efficient alternative for the decolourization of urban and drinking water streams and elucidate the potential of machine learning models for accurate prediction & elevation of adsorption processes with less experimentation in water purification applications.

Polishing of painting process effluents through adsorption with biochar from winemaking residues

A real industrial effluent from the pre-treatment and painting processes was polished through adsorption using alternative biochar derived from grape pomace wastes. The biochar was produced in a pilot-scale plant from composted grape pomace. Biochar showed an equilibrium between acidic and basic groups on the surface. The presence of irregular cavities in the structure and mesopores was confirmed by analyzing N₂ physisorption and SEM. Concerning the effluent, Ni and Zn were the main problematic elements. The adsorption isotherms and kinetics of Ni and Zn from the effluent using the biochar could be represented by the Henry, pseudo-first-order, and pseudo-second-order models, respectively. Adsorption equilibrium was reached within 60 min for Ni and Zn present in the real effluent. Besides, the adsorption process was endothermic, favorable, and spontaneous. These results demonstrate that Zn and Ni metals were successfully removed from the industrial effluent, presenting final concentration values within the limit of legislation for effluent disposal in agricultural soil.

Research and Application Progress of Geopolymers in Adsorption: A Review

Geopolymer is a porous inorganic material with a three-dimensional mesh structure, good mechanical properties, a simple preparation process (no sintering) and a low economic cost, and it is environmentally friendly. Geopolymer concrete has been widely used in the construction field, and many other studies have revealed that geopolymer will become one of the most promising inorganic materials with unique structure and properties. This paper provides a review of the development and current status of geopolymers and briefly explains the effects of material proportioning, experimental factors and activators on geopolymer performance. Because of the advantages of high specific surface area and high porosity, geopolymers could be used as adsorbent materials. This paper summarizes the research progresses of the adsorption of metal cations, anions, dyes, and gases by geopolymers, which emphasizes the geopolymer membranes in adsorption, and discusses the challenges and opportunities for the development of more efficient, sustainable and practical adsorption protocols.

A State-of-the-Art Review on Innovative Geopolymer Composites Designed for Water and Wastewater Treatment

There is nothing more fundamental than clean potable water for living beings next to air. On the other hand, wastewater management is cropping up as a challenging task day-by-day due to lots of new additions of novel pollutants as well as the development of infrastructures and regulations that could not maintain its pace with the burgeoning escalation of populace and urbanizations. Therefore, momentous approaches must be sought-after to reclaim fresh water from wastewaters in order to address this great societal challenge. One of the routes is to clean wastewater through treatment processes using diverse adsorbents. However, most of them are unsustainable and quite costly e.g. activated carbon adsorbents, etc. Quite recently, innovative, sustainable, durable, affordable, user and eco-benevolent Geopolymer composites have been brought into play to serve the purpose as a pretty novel subject matter since they can be manufactured by a simple process of Geopolymerization at low temperature, lower energy with mitigated carbon footprints and marvellously, exhibit outstanding properties of physical and chemical stability, ion-exchange, dielectric characteristics, etc., with a porous structure and of course lucrative too because of the incorporation of wastes with them, which is in harmony with the goal to transit from linear to circular economy, i.e., "one's waste is the treasure for another". For these reasons, nowadays, this ground-breaking inorganic class of amorphous alumina-silicate materials are drawing the attention of the world researchers for designing them as adsorbents for water and wastewater treatment where the chemical nature and structure of the materials have a great impact on their adsorption competence. The aim of the current most recent state-of-the-art and scientometric review is to comprehend and assess thoroughly the advancements in geo-synthesis, properties and applications of geopolymer composites designed for the elimination of hazardous contaminants viz., heavy metal ions, dyes, etc. The adsorption mechanisms and effects of various environmental conditions on adsorption efficiency are also taken into account for review of the importance of Geopolymers as most recent adsorbents to get rid of the death-defying and toxic pollutants from wastewater with a view to obtaining reclaimed potable and sparkling water for reuse offering to trim down the massive crisis of scarcity of water promoting sustainable water and wastewater treatment for greener environments. The appraisal is made on the performance estimation of Geopolymers for water and wastewater treatment along with the three-dimensional printed components are characterized for mechanical, physical and chemical attributes, permeability and Ammonium (NH4+) ion removal competence of Geopolymer composites as alternative adsorbents for sequestration of an assortment of contaminants during wastewater treatment.