Water-insoluble Material Research Articles

An N-Rich Polymer for the Selective Recovery of Gold from Wastewater.

The recovery of valuable gold from wastewater is of great interest because of the widespread use of the precious metal in various fields and the pollution generated by gold-containing wastes in water. In this paper, a water-insoluble cross-linked adsorbent material (TE) based on cyanuric chloride (TCT) and ethylenediamine (EDA) was designed and used for the adsorption of Au(III) from wastewater. It was found that TE showed extremely high selectivity (D = 49,213.46) and adsorption capacity (256.19 mg/g) for Au(III) under acidic conditions. The adsorption rate remained above 90% eVen after five adsorption-desorption cycles. The adsorption process followed the pseudo-first-order kinetic model and the Freundlich isotherm model, suggesting that physical adsorption with a multilayer molecular overlay dominates. Meanwhile, the adsorption mechanism was obtained by DFT calculation and XPS analysis, and the adsorption mechanism was mainly the electrostatic interaction and electron transfer between the protonated N atoms in the adsorbent (TE) and AuCl4-, which resulted in the redox reaction. The whole adsorption process was the result of the simultaneous action of physical and chemical adsorption. In conclusion, the adsorbent material TE shows great potential for gold adsorption and recovery.

Chemical Analysis of Arenga Palm Sugar and Its Relationship with Consumer Acceptability

In Indonesia, the quality of Arenga palm sugar must meet certain chemical component requirements, including water-insoluble material, water content, ash content, reducing sugar content, and sucrose content. The heating process of the sap water can affect the quality of the palm sugar, as well as the preferences of consumers because it affects sensory attributes. The aroma and taste of palm sugar are mainly influenced by the levels of reducing sugar and sucrose. The research objective is to determine the correlation between the chemical components of palm sugar and its consumer acceptance by comparing the data from different regions. The explanatory sequential method is used, which involves two tests for sensory analysis: the Check-All-That-Apply (CATA) test and the ANOVA test. The Pearson correlation method is used to analyze the correlation between palm sugar chemistry and customer acceptance. The research revealed that the water-insoluble material and sucrose content of palm sugar did not meet the Indonesian national standards (SNI). Sucrose sugar content is negatively correlated with the aroma of palm sugar, where the panelists’ preference for palm sugar increased if the sucrose sugar content was lower.

Target-Induced AIE Effect Coupled with CRISPR/Cas12a System Dual-Signal Biosensing for the Ultrasensitive Detection of Gliotoxin.

Here, a novel rapid and ultrasensitive aptamer biosensor was designed for target-induced activation of AIE effect and followed by the activation of Crispr Cas12a (LbCpf1)-mediated cleavage to achieve dual-signal detection. The prepared DNA building blocks contain the target aptamer, ssDNA-Fc, and Activator1. In this system, the activation mode was divided into two steps. First, when the target interacts with the aptamers, the DNA building blocks would be disintegrated rapidly, releasing a mass of Ac1, generating ETTC-dsDNA aggregated to produce a fluorescence signal by the AIE effect. Second, with the release of Ac2, LbCpf1-crRNA was activated, which greatly improves the ssDNA-Fc cleavage efficiency to render signal amplification and ultrasensitive detection of the target. Satisfactorily, using this approach to detect gliotoxin, optimal conditions for detection was achieved for reducing the detection time to 55 min, achieving a low detection limit of 2.4 fM and a satisfactory linear in the range of 50 fM to 1 nM, which addressed the shortcoming of a weak electrochemical signal in previous sensors. The water-insoluble AIE material was coupled with DNA to obtain water-soluble ETTC-dsDNA and successfully introduced into the sensor system, with a low detection limit of 5.6 fM. Subsequently, the biosensor combined with handheld electrochemical workstation was successfully applied in the detection of gliotoxin in five actual samples, with a detection range of 32.0 to 2.09 × 108 pM. This strategy not only provides a novel and effective detection platform for mycotoxins in complex food matrices but also opens a promising avenue for various molecules detection in imaging and disease diagnosis.

Engineering in the Production of Crystal Coconut Sugar Enriched with Vitamin A and its Preference Tests for Consumers

Coconut sugar is a food product that has the potential to be fortified with Vitamin A. This study aims to assess the quality of crystalline coconut sugar with vitamin A and test its preference for consumers. The experimental design used Split Plot Design with two treatment factors and 4 replications. The first treatment as the Main Plot (Main Plot) is the type of raw material for crystalline coconut sugar, which consists of 2 variations, namely: M1 = pure sap, and M2 = printed coconut sugar + 5% granulated sugar. The second treatment as a sub-plot was the proportion between palm oil as a solvent and carrots as a source of carotene (Vitamin A), which consisted of 3 variations, namely: S1= 1 : 1 (v/b), S2 = 1 : 2 (v/b), and S3= 2 : 1 (v/b). Physicochemical data were analyzed by F test and followed by 5% DMRT test, while organoleptic properties data were analyzed by Friedman test and followed by multiple comparison test. The best treatment was analyzed by the effectiveness index method. The results showed that a good raw material for producing crystalline coconut sugar with low reducing sugar content and high sucrose content was pure coconut sap. The proportion between palm oil and carrots which can produce crystalline coconut sugar with high levels of carotene (pro vitamin A) is 1 : 2 (v/b). The treatment combination that can produce crystalline coconut sugar with vitamin A with quality according to SNI-SII No.0268-85 is the treatment of the type of raw material for crystalline coconut sugar from pure coconut sap and the proportion of palm oil as a solvent with carrots as a source of carotene 1 : 2 ( v/b). This combination of treatments produced crystalline coconut sugar with physicochemical and organoleptic properties as follows: carotene content of 9.015 mg/100g of material or the equivalent of 752 RE (Retinol equivalent), water content of 3.617 percent, total sugar content of 81.071 percent, sucrose content of 75.627 percent, sugar content 5.434 percent reduction, 0.753 percent ash content and 0.197 percent water insoluble material content, "very smooth" texture, "creamy" color, "strong" coconut aroma, "not felt" carrot unpleasant smell and level of consumer acceptance (preference) "like".

A single-parameter hygroscopicity model for functionalized insoluble aerosol surfaces

Abstract. The impact of molecular level surface chemistry for aerosol water-uptake and droplet growth is not well understood. In this work, spherical, nonporous, monodisperse polystyrene latex (PSL) particles treated with different surface functional groups are exploited to isolate the effects of aerosol surface chemistry for droplet activation. PSL is effectively water insoluble and changes in the particle surface may be considered a critical factor in the initial water uptake of water-insoluble material. The droplet growth of two surface modified types of PSL (PSL-NH2 and PSL-COOH) along with plain PSL was measured in a supersaturated environment with a Cloud Condensation Nuclei Counter (CCNC). Three droplet growth models – traditional Köhler (TK), Flory–Huggins Köhler (FHK) and the Frenkel–Halsey–Hill adsorption theory (FHH-AT) were compared with experimental data. The experimentally determined single hygroscopicity parameter, κ, was found within the range from 0.002 to 0.04. The traditional Köhler prediction assumes Raoult's law solute dissolution and underestimates the water-uptake ability of the PSL particles. FHK can be applied to polymeric aerosol; however, FHK assumes that the polymer is soluble and hydrophilic. Thus, the FHK model generates a negative result for hydrophobic PSL and predicts non-activation behavior that disagrees with the experimental observation. The FHH-AT model assumes that a particle is water insoluble and can be fit with two empirical parameters (AFHH and BFHH). The FHH-AT prediction agrees with the experimental data and can differentiate the water uptake behavior of the particles owing to surface modification of PSL surface. PSL-NH2 exhibits slightly higher hygroscopicity than the PSL-COOH, whereas plain PSL is the least hygroscopic among the three. This result is consistent with the polarity of surface functional groups and their affinity to water molecules. Thus, changes in AFHH and BFHH can be quantified when surface modification is isolated for the study of water-uptake. The fitted AFHH for PSL-NH2, PSL-COOH, and plain PSL is 0.23, 0.21, and 0.18 when BFHH is unity. To simplify the use of FHH-AT for use in cloud activation models, we also present and test a new single parameter framework for insoluble compounds, κFHH. κFHH is within 5 % agreement of the experimental data and can be applied to describe a single-parameter hygroscopicity for water-insoluble aerosol with surface modified properties.

Elderberry Concentrate Juice Industrial By-Products Characterization and Valorisation

The elderberry juice industry generates by-products that can be valorised as a source of valuable compounds, namely anthocyanins and carbohydrates recovered from pomace and retentate. This work aims to valorise the anthocyanins and carbohydrates present in pomace and retentate, focused on the analysis and characterization of the polysaccharides present and their use for the stability of pink beverages. The present work shows that pomace contains 50% of carbohydrates, in which glucose and xylose are the major constituents, probably arising from cellulose and xyloglucans of cell walls polysaccharides and from the moiety of main anthocyanins present in berry skin. The concentrated juice is rich mainly in free sugars (55%), glucose and fructose, containing also pectic polysaccharides. However, a large amount of compounds are retained in the ultrafiltration membranes of 100 kDa, constituting the retentate, comprising 52% of water insoluble material. The remaining 48% constitutes the water-soluble fraction, composed of 47% of free sugars, mainly fructose (80%), and 14% of polymeric material constituted by 38% of pectic polysaccharides and 44% of anthocyanins. The use of the colourant in the form of a complex pectic polysaccharides-anthocyanins allowed to achieve a higher colour stability than the isolated anthocyanins, over more than 22 days. This property allowed to use the retentate water soluble fraction as a natural colourant ingredient to develop a stable pink tonic water.

Water uptake of subpollen aerosol particles: hygroscopic growth, cloud condensation nuclei activation, and liquid–liquid phase separation

Abstract. Pollen grains emitted from vegetation can release subpollen particles (SPPs) that contribute to the fine fraction of atmospheric aerosols and may act as cloud condensation nuclei (CCN), ice nuclei (IN), or aeroallergens. Here, we investigate and characterize the hygroscopic growth and CCN activation of birch, pine, and rapeseed SPPs. A high-humidity tandem differential mobility analyzer (HHTDMA) was used to measure particle restructuring and water uptake over a wide range of relative humidity (RH) from 2 % to 99.5 %, and a continuous flow CCN counter was used for size-resolved measurements of CCN activation at supersaturations (S) in the range of 0.2 % to 1.2 %. For both subsaturated and supersaturated conditions, effective hygroscopicity parameters, κ, were obtained by Köhler model calculations. Gravimetric and chemical analyses, electron microscopy, and dynamic light scattering measurements were performed to characterize further properties of SPPs from aqueous pollen extracts such as chemical composition (starch, proteins, DNA, and inorganic ions) and the hydrodynamic size distribution of water-insoluble material. All investigated SPP samples exhibited a sharp increase of water uptake and κ above ∼95 % RH, suggesting a liquid–liquid phase separation (LLPS). The HHTDMA measurements at RH >95 % enable closure between the CCN activation at water vapor supersaturation and hygroscopic growth at subsaturated conditions, which is often not achieved when hygroscopicity tandem differential mobility analyzer (HTDMA) measurements are performed at lower RH where the water uptake and effective hygroscopicity may be limited by the effects of LLPS. Such effects may be important not only for closure between hygroscopic growth and CCN activation but also for the chemical reactivity, allergenic potential, and related health effects of SPPs.

Cellhesion VP enhances the immunomodulating potential of human mesenchymal stem cell-derived extracellular vesicles

Mesenchymal stem cell (MSC) transplantation is a promising therapy for regenerative medicine. However, MSCs grown under two-dimensional (2D) culture conditions differ significantly in cell shape from those in the body, with downregulated stemness genes and secretion of paracrine factors. Here, we evaluated the effect of 3D culture using Cellhesion VP, a water-insoluble material composed of chitin-based polysaccharide fibers, on the characteristics of human Wharton's jelly-derived MSCs (hMSCs). Cellhesion VP significantly increased cell proliferation after retrieval. Transcriptome analyses suggested that genes involved in cell stemness, migration ability, and extracellular vesicle (EV) production were enhanced by 3D culture. Subsequent biochemical analyses showed that the expression levels of stemness genes including OCT4, NANOG, and SSEA4 were upregulated and migration capacity was elevated in 3D-cultured hMSCs. In addition, EV production was significantly elevated in 3D cells, which contained a distinct protein profile from 2D cells. Gene and drug connectivity analyses revealed that the 2D and 3D EVs had similar functions as immunomodulators; however, 3D EVs had completely distinct therapeutic profiles for various infectious and metabolic diseases based on activation of disease-associated signaling pathways. Therefore, EVs from Cellhesion VP-primed hMSCs offer a new treatment for immune and metabolic diseases.

Browning, Starch Gelatinization, Water Sorption, Glass Transition, and Caking Properties of Freeze-dried Maca ( Lepidium meyenii Walpers) Powders.

The browning, gelatinization of starch, water sorption, glass transition, and caking properties of freeze-dried maca ( Lepidium meyenii Walpers) powders were investigated and compared with a commercial maca powder. The freeze-dried maca powders had lower optical density (browning) and higher enthalpy change for starch gelatinization than the commercial maca. This resulted from a difference in thermal history. The equilibrium water contents of the freeze-dried maca powders were higher than those of commercial maca at each water activity ( a w ) because of differences in amorphous part. The glass transition temperature ( T g ) was evaluated by differential scanning calorimetry. There was a negligible difference in the anhydrous T g (79.5–80.2 ºC) among the samples. The T g -depression of freeze-dried maca powders induced by water sorption was more gradual than that of the commercial maca due to a difference in water insoluble material content. From the results, critical water activity ( a wc ) was determined as the a w at which T g becomes 25 ºC. There was negligible caking below a w = 0.328. At higher a w , the degree of caking remarkably increased with a large variation depending on the samples. The degree of caking could be described uniformly as a function of a w / a wc . From these results, we propose an empirical approach to predict the caking of maca powders.

Development history and synthesis of super-absorbent polymers: a review

Super-absorbent polymers (SAPs) refer to a three-dimensional network polymer, water-swellable, water-insoluble, organic or inorganic material that can absorb thousands of times its own weight of distilled water. It is widely used in various fields, such as: agricultural, biomedical, daily physiological products, separation technology and wastewater treatment. In the review, the development history of superabsorbent polymers since 1961 is described, and the polymerization methods of superabsorbent polymers and the wide-ranging use of this type of polymers in life are described in detail. The article introduces four basic polymerization methods, bulk polymerization, solution polymerization, suspension polymerization and radiation polymerization from the preparation methods and types. Not only the detailed methods of polymerization but also their respective advantages and disadvantages are introduced. In recent years, new progress has been made in polymerization methods, for example, in-situ polymerization to obtain an onion-like multilayer tube cellulose hydrogel. The hydrogel has super-absorbent properties, and the water swelling mechanism is briefly introduced. Finally, the latest advances in super-absorbent polymers are pointed out.

Removal of Fluoride Ions in Stored Drinking Water by Triethylamine Chemically Modified Polyethylene Containers

This paper reports the removal of fluoride ions in stored drinking water by a container made from chemically modified polyethylene material. To anchor triethylamine within the structure of the polyethylene material and improve its value, the polyethylene was first heated to melting. To the molten material, hot vegetable oil was added slowly with continuous heating followed by a strongly basic hydrogen peroxide solution and then activated with triethylamine to produce a water-insoluble material that is not a threat to life. The resulting synthesized products were characterized using FTIR and 13C NMR after each step. The triethylamine-activated epoxy material was molded into a 1 l container which was cured for 3 h in an electric oven at 150 °C to form a hard mechanically strong container. It was then used for water storage and removal of dissolved fluoride ions. Its ability to remove fluoride ions was based on complexation reaction between the fluoride ions and quaternary ammonium compounds. The results obtained showed that sorption was best at pH values between 6.0 and 8.0. It was observed that a 40% removal efficiency was achieved from a solution containing 12.5 mg l−1 of fluoride ions in less than 7 days of storage at the physiological pH of water. The existence of sulfate and nitrate ions had no observed significant effect on the fluoride removal process. However, chloride ions affected the removal of the fluoride ions and were therefore used to regenerate the container for reuse. The modification process is a sustainable method to manage the polyethylene pollution menace. This study revealed that the container has a potential application for the remediation of fluoride-laden waters in the rural areas during the water storage process to make it safe for domestic consumption.

Waste mitigation: From an effluent of apple juice concentrate industry to a valuable ingredient for food and feed applications

Retentate is a by-product of the concentrate apple juice industry, resultant from clarification through an ultrafiltration process. It has a liquid to sludgy appearance, with 8% of total solids content, usually discarded as industrial waste, conveyed as wastewater directly to the sewage plant. However, its origin and expected composition may allow to define its use as a source of valuable compounds as well as its application in food and feed. The present work shows that retentate is very rich in carbohydrates, namely 40% fructose (dry weight), glucose (8%), oligosaccharides (5%), and polysaccharides (3%). It is also rich in protein (8%) and an available and inexpensive source of β-sitosterol (0.6%). This was the major sterol identified, accounting for 21% of total lipophilic compounds recovered by n-hexane. The retentate suspension was successfully used as nutritive medium for production of cider by a microbrewery and the protein-rich water insoluble material (28% of protein) was successfully used in feed formulations for racing pigeons.

Antioxidant, Antimicrobial and Physicochemical Properties of Turmeric Extract-Loaded Nanostructured Lipid Carrier (NLC)

The objective of this research was to encapsulate turmeric extract as a water-insoluble bioactive material by nanostructured lipid carrier (NLC). Turmeric extract loaded NLC (T-NLC) was produced by high shear homogenization method. The average size of T-NLC was 112.4nm and it showed good physical stability, and a sustained release pattern. Higuchi model fit in vitro release of turmeric extract from NLC the best. The antioxidant activity of T-NLC was significantly higher than free turmeric extract. The results of microbiological tests by agar-dilution method showed that NLC had higher antimicrobial activity than free turmeric extract against all examined gram negative bacilli microorganisms. The results indicate that T-NLC can be used in food products with high functional effects.

Mathematical modeling of the capillary rise of liquids in partially soluble particle beds

One of the most widely used techniques for evaluating the wettability of powdered foods is the capillary rise method, in which the contact angle is usually estimated using the classical Washburn model. However, this model does not take into account the effect of the dissolution of the particle bed in the rising process, which is an important limitation for its application to many powdered foods. This work presents a new mathematical model for the analysis of capillary rise data considering the partial dissolution of the particle bed. As in the case of the classical Washburn model, the proposed model, designated Dissolution-Modified Washburn Model (DM-Washburn), was obtained by the integration of the Navier-Stokes equation, but introducing a dependency of the capillary diameter as a function of meniscus position and time as a strategy to quantify the dissolution effects. The comparison between the DM-Washburn and the classical Washburn models in terms of quality of fit was performed using experimental data of capillary rise in d-(+)-glucose and lactose using as wetting liquids pure water and aqueous solutions of these two materials with concentrations up to saturation. The DM-Washburn model provided better fit to the height versus time data, with mean relative deviation (MRD) values lower than 5% for all tested conditions. Further, the estimates of contact angle obtained with the DM-Washburn model showed to be independent of the carbohydrate concentration in the wetting liquid, differently from what was observed using the classical Washburn model. Additionally, tests with microcrystalline cellulose (MCC), a water insoluble material, showed the consistency of the DM-Washburn model in conventional capillary experiments, i.e., without significant dissolution of the particle bed. The obtained results indicate that the model has great potential for evaluating the wettability of soluble materials.

Povidone-Iodine-Based Polymeric Nanoparticles for Antibacterial Applications.

As microbial contamination is becoming more and more serious, antibacterial agents play an important role in preventing and removing bacterial pathogens from microbial pollution in our daily life. To solve the issues with water solubility and antibacterial stability of PVP-I2 (povidone-iodine) as a strong antibacterial agent, we successfully obtain hydrophobic povidone-iodine nanoparticles (povidone-iodine NPs) by a two-step method related to the advantage of nanotechnology. First, the synthesis of poly(N-vinyl-2-pyrrolidone-co-methyl methacrylate) nanoparticles, i.e., P(NVP-MMA) NPs, was controlled by tuning a feed ratio of NVP to MMA. Then, the products P(NVP-MMA) NPs were allowed to undergo a complexation reaction with iodine, resulting in the formation of a water-insoluble antibacterial material, povidone-iodine NPs. It is found that the feed ratio of NVP to MMA has an active effect on morphology, chemical composition, molecular weight, and hydrophilic-hydrophobic properties of the P(NVP-MMA) copolymer after some technologies, such as SEM, DLS, elemental analysis, 1H NMR, GPC, and the contact angle test, were used in the characterizations. The antibacterial property of povidone-iodine NPs was investigated by using Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) as model bacteria with the colony count method. Interestingly, three products, such as glue, ink, and dye, after the incorporation of povidone-iodine NPs, show significant antibacterial properties. It is believed that, with the advantage of nanoscale morphology, the final povidone-iodine NPs should have great potential for utilization in various fields where antifouling and antibacterial properties are highly required.

Fundamental melting process of water-insoluble phase change material immersed in water

Fundamental melting process of water-insoluble phase change material immersed in water

Characterization of pyrolysis products produced from different Nordic biomass types in a cyclone pilot plant

Pyrolysis is a promising thermochemical technology for converting biomass to energy, chemicals and/or fuels. The objective of the present paper was to characterize fast pyrolysis products and to study pyrolysis oil fractionation. The products were obtained from different Nordic forest and agricultural feedstocks in a pilot scale cyclone pyrolysis plant at three different reactor temperatures. The results show that the main elements (C, H and O) and chemical compositions of the products produced from stem wood, willow, forest residue and reed canary grass are in general terms rather similar, while the products obtained from bark differ to some extent. The oil produced from bark had a higher H/Ceff ratio and heating value which can be correlated to a higher amount of pyrolytic lignin and extractives when compared with oils produced from the other feedstocks. Regardless of the original feedstock, the composition of the different pyrolysis oil fractions (condensed and aerosol) differs significantly from each other. However this opens up the possibility to use specifically selected fractions in targeted applications. An increased reactor temperature generally results in a higher amount of water and water insoluble material, primarily as small lignin derived oligomers, in the produced oil.

Evaluation of some natural water-insoluble cellulosic material as lost circulation control additives in water-based drilling fluid

Circulation losses have always been a serious and expensive problem to the drilling industry. Even with the best drilling practices circulation losses do occur. In order to reduce such losses to acceptable level fluid Loss Control Material (LCM) is used.In this work, three natural water-insoluble cellulosic materials; peanut hulls, bagasse and sawdust were investigated as lost circulation control materials. One hundred and eight different LCM samples made of various materials were tested with mud. The experiments were conducted in a permeability plugging apparatus (PPA) at a differential pressure of 100psi and 300psi, using 10, 60 and 90 ceramic discs. The performance of each LCM sample was determined based on the amount of spurt loss and total fluid loss of the mud according to the American Petroleum Institute (API) standard. The obtained results showed that, the amount of the fluid loss depends on the LCM material, concentration and size distribution, testing results show that, the peanut gives the best results among the bagasse and sawdust, especially fine size which exhibited better results in the filtration characteristics due to the better filling properties of this size. Peanut hulls, bagasse and sawdust show a slight effect on the rheological properties of the mud. The results were discussed on light of particle size distribution.

Subcritical Hydrothermal Liquefaction of Microalgae Residues as a Green Route to Alternative Road Binders

The valorization of Scenedesmus sp. microalgae byproducts was investigated, as a potential route for the production of road binders from renewable sources. Under hydrothermal liquefaction conditions, a water-insoluble viscous material was obtained in a ca. 55% yield, which consists of an oily fatty acid-based fraction mixed with organic and inorganic solid residues (up to 22%). Although the chemical composition of the obtained materials completely differs from that of petroleum-based bitumen, similar viscoelastic properties were observed in some cases, depending on the hydrothermal liquefaction experimental conditions. A rheological simple material could thus be obtained, which compared well with a bitumen reference.

Potential of inorganic polymers (geopolymers) made of halloysite and volcanic glass for the immobilisation of tailings from gold extraction in Ecuador

In the present study, inorganic polymers (geopolymers) were synthesised using volcanic glass, calcined halloysite-rich clay and mine tailings, all from Ecuador. In addition to the possibility of making a geopolymer binder from these materials, the influence of geopolymerisation on the immobilisation of the mine tailings was investigated. The research focused on the effect of synthesis conditions on the strength, microstructure and composition of the geopolymer binder and on the leaching behaviour of heavy metals and Arsenic (As). A water insoluble material with a compressive strength of 30MPa was synthesised using a Na-silicate activator (composition in wt.%, Na2O: 15; SiO2: 13; H2O: 72) and using 110kg of activating solution per tonne of raw material. It was shown that incorporation of mine tailings in the geopolymers did not have an effect on the mechanical properties. The production of geopolymer based tailing pastes thus shows potential for use on the mining site, for example as a capping material of tailing ponds. Geopolymerisation influences pH-dependent heavy metal leaching but does not cause a complete immobilisation of heavy metals and As. In general, the leaching of heavy metals is limited, below the regulatory concentrations for using the geopolymers in building materials. An exception on this are Cu and As, which show increased mobility due to the higher pH obtained in the geopolymerisation.