Red Gypsum Research Articles

Self-cleaning ability of gypsum-cement-pozzolan binders based on thermally processed red gypsum waste of titanium oxide manufacture

A recycling solution for landfilled red gypsum waste originating from titanium oxide manufacture (sulfate method), is proposed. The waste consisted mainly of gypsum, goethite, and free titanium oxide as indicated by thermal and x-ray diffraction analyses, and scanning electron microscopy. Photocatalytically active beta gypsum, with physical properties typical for building gypsum, was obtained by thermal treatment (140–190 °C) of the waste. On its basis, gypsum-cement-pozzolan binders of variable beta gypsum content were prepared. The binders ensured compressive strength of at least 9 MPa at 28 days, structural stability over time, and appropriate distribution of titanium oxide, irrespective of the beta gypsum content in the mixture. Optimal water resistance and self-cleaning ability were achieved for 63–70% beta gypsum content, which triggered a small increase (∼5%) in porosity. The results suggest the utilization of the developed binder as self-cleaning plaster on structures exposed to atmospheric pollutants.

Preparation of calcium sulfate from recycled red gypsum to neutralize acidic wastewater and application of high silica residue

Preparation of calcium sulfate from recycled red gypsum to neutralize acidic wastewater and application of high silica residue

Synthesis of glycerol carbonate from industrial by-products by alcoholysis of urea: Crude glycerol and red gypsum

In this study, a heterogeneous catalyst was developed from red gypsum for the synthesis of glycerol carbonate through a glycerolysis reaction with urea. Under optimum reaction conditions, a simple heat treatment on bare red gypsum in a static air environment produces an 87% yield of the targeted glycerol carbonate product. The higher catalytic activity of the calcined catalyst is due to its basic characteristics and the presence of different phases of anhydrite CaSO4 with additional elements, especially an active hematite (Fe2O3) phase. The catalytic process was also found to be insensitive to the type of flowing gas that was used to remove the evolved ammonia gas, whereby, either inert nitrogen gas or reactive air containing oxygen did not significantly impact the glycerol carbonate yield. Indeed, with a promising yield, the developed catalytic system was able to directly synthesise glycerol carbonate from industrial crude glycerol from a biodiesel plant. The red gypsum-based catalytic system seems resistant to the presence of a certain level of moisture and other impurities in crude glycerol. The catalyst efficiency is being retained for consecutive reaction cycles, which are subsequently reused for the next batch reaction without requiring any pre-treatment.

Influence of different types and contents of gypsum on mechanical properties and porosity of sulphate activated binder

Fly ash (FA) is pozzolanic, while blast furnace slag (GGBS) is latent hydraulic. These two materials react slowly in the presence of water to harden. Adding an alkali activator such as strong hydroxide could boost the hardening process, but the safe handling of highly corrosive materials is the primary concern. Therefore, the present work prescribed various types of gypsum to activate FA and GGBS as a binder phase for making mortar. It aimed to investigate the influence of different types and contents of gypsum on the mechanical properties and porosity of sulphate-activated binder. Gypsum is a less corrosive material to provide calcium and sulphate ions for activating GGBS and FA. The main component of gypsum was calcium sulphate. Gypsum provides calcium sources that promote more C-S-H to be formed. A few types of gypsum were studied with their effect on FA/GGBS blended mortar. Furthermore, the mechanical strength and porosity of gypsum-activated GGBS/FA blended mortar were assessed. The mortar containing white gypsum exhibited the best mechanical performance among all types of gypsum. On the other hand, red gypsum and dental gypsum were established to be more effective in pore refinements, lowering the mortar’s total porosity. In conclusion, white gypsum is the most suitable material for activating the FA/GGBS blend among the various types of gypsum examined.

The Grease Formulation Using Waste Substances from Palm Oil Refinery and Other Industrial Wastes: A Review

Many applications use Spent Bleaching Earth (SBE) despite being considered hazardous waste from the palm oil refinery process. Its production increases yearly, similar to waste cooking oil (WCO). The SBE is known as a thickener in grease formulation. The same goes for red gypsum, waste motor oil, stearic acid, and lithium hydroxide monohydrate. They are all considered thickeners but have different durability in protecting base oil in grease. Then, previous studies revealed their performances with side effects detection against the environment and human bodies. Cooking oil is a heat transfer medium for serving foods with higher amounts of unsaturated fatty acids. The number of fatty acids might change after cooking oil consumption and become highly demanded due to the chemical properties of density, viscosity and fatty acids. Nowadays, people lack awareness of the importance of recycling palm oil waste. They intend to dispose of it instead of recycling it for sustainable energy resources. Therefore, this paper will discuss the grease formulation, contaminant available in WCO, its treatment, issues regarding different thickener consumption, treatment against Spent Bleaching Earth (SBE), and propose the safe thickener and additives for future intakes. This study found that adding Fume Silica (F.S.) as a thickener and Molybdenum Disulfide (MoS2) enhanced the grease stability. Further treatment against SBE (remove residue oil) and WCO (metal elements, undesired impurities and water content) is necessary for providing good quality formulated grease.

Leaching Behaviour of Synthetic Leachate through a Sewage Sludge and Red Gypsum Composite as Intermediate Landfill Cover

This paper examines the environmental impact of the use of compacted sewage sludge:red gypsum (SS:RG) mixture as intermediate landfill cover in terms of yield and quality of leachate as characterised by hydraulic conductivity and leaching behaviour. A series of column tests using the constant head method is carried out by percolating the synthetic leachate through samples that have been compacted at various degrees (60, 70, 75, 80 and 85%). The leachate quality is monitored at pre-determined days for pH, COD, Cu, Fe and Zn. In general, hydraulic conductivity decreases in three stages, in which the first stage is mainly attributed to the particle rearrangement and hydration of calcium silicate hydrate (CSH). The hydration of CSH increases the pH, which causes the heavy metal to precipitate and be entrapped within the matrices of CSH gel, thereby further reducing the porosity and hydraulic conductivity. A minimum of 75% compaction has shown favourable final porosity, hydraulic conductivity, and leachate quality, although a minimum of 80% compaction is recommended in order to achieve a satisfactory compressive strength of greater than 345 kPa for a landfill operation.

Resource utilization of strongly acidic wastewater and red gypsum by a harmless self-treatment process

The acidic wastewater and red gypsum generated by the titanium dioxide (TiO2) industry pose a great threat to humans and the environment. In order to achieve low-cost and high-benefit resource utilization of acidic wastewater and red gypsum, a harmless process for the self-treatment of acidic wastewater and red gypsum as well as for the recovery of valuable resources such as Ti, Fe, Ca, and S is proposed in this study. Acidic wastewater was innovatively used to purify red gypsum while reducing its acidity. The results showed that Fe, Ti, Al, Mn, and Mg impurities in red gypsum could be leached efficiently by the acidic wastewater, resulting in the calcium sulfate products, which can be used as a substitute for natural gypsums in industrial production. Subsequently, phosphoric acid was directly added to the Ti-rich filtrate and stirred at 85 ℃ for 45 min, so that the titanium was converted into titanium phosphate precipitation, with an optimal titanium recovery ratio of 94.86%. After recovering Ti, the filtrate was used again to purify red gypsum. Finally, the pH of the low acidity solution was treated by oxidation and precipitation, and filtered to obtain the Fe-rich filter residue and ammonium sulfate solution. The Fe-rich filter residue could be used in the metallurgical industry, and the ammonium sulfate solution was evaporated and crystallized to obtain the (NH4)2SO4 product. The harmless self-treatment process not only facilitated the resource utilisation of acidic wastewater and red gypsum, but also solved the pollution problems caused by wastewater and solid waste in the TiO2 industry.

From high-volume industrial waste to new ceramic material: The case of red gypsum muds in the TiO2 industry

The present study aims to apply the principles of circular economy, using special inorganic waste (in particular, red gypsum muds from a TiO2 plant in Tuscany, Italy) to produce ceramic materials for the construction and building industries. Red gypsum (RG) muds produced during more than 10 years of industrial processing were chemically and mineralogically characterized by X-ray fluorescence spectrometry (XRF), X-ray powder diffraction (XRPD), scanning electron microscopy with energy dispersive X-ray spectrometer (SEM/EDS), and thermal analyses (TA). The analyses testify that RG waste production is chemically and mineralogically constant over time, and therefore suitable to be used as a secondary raw material in industrial ceramic production. Ceramic specimens have been realized using an extremely high amount of the RG waste (up to 70%) and characterized using the same chemical-mineralogical techniques, revealing that anhydrite, pyroxene, and Fe/Ti oxides are the main crystalline phases, embedded in a glassy compact matrix. Overall results indicate that the production of ceramic materials could represent a definitive and sustainable solution for the problematic management of the large volumes of RG waste deriving from TiO2 plants.

Foamed Concrete using Red Gypsum and Palm Oil Fuel Ash: A Sustainable Building Material

Concrete is the most commonly used building material. Even then, it has a drawback that it hasheavy density. Hence, researches are progressing everywhere to develop a new building material, which has low density, less water absorption as well as economical. And here lies the importance of foamed concrete. Foamed concrete is a type of lightweight concrete in which stable foam is used as the main ingredient. Stable foam is produced from standard foaming agent using a foam generator. The peculiarity of foamed concrete is that no coarse aggregate is used in it. An attempt is made in this research to use palm oil fuel ash as a partial replacement for cement and red gypsum as a partial replacement for manufactured sand. Both of these materials are waste materials and are abundantly available. The concrete made up of this will be more sustainable as well as economical. By adjusting the addition of stable foam, foamed concrete of various densities can be developed. Foamed concrete blocks made up of these materials can be used for load bearing as well as non-load bearing masonry works. It has been observed that the addition of Palm Oil Fuel Ash and Red Earth has improved the properties of foamed concrete.

Digestate improved birch (Betula pendula) growth and reduced leaf trace element contents at a red gypsum landfill

Revegetation of industrial landfills and mine tailing may restore key soil functions and reduce the environmental impacts of contaminants. These marginal sites are often characterized by phytotoxic levels of trace elements (TE) (Cu, Fe, Mn, and Zn) and low nutrient status (N, P, and K). The aim of this study was to test the effect of digestate and bacterial inoculation on soil physicochemical properties (pH, CaCl2 extractable Mn, and microbial enzyme activities) and birch (Betula pendula) growth and physiology on a red gypsum substrate in a lab-to-field experimental approach. The biomass of birches amended with digestate (D0.05% N) was on average 2- and 6-fold greater than that of control birch in the laboratory and field experiments, respectively. A higher concentration of digestate (0.1% N) had an inhibitory effect on plant growth, and reduced the survival rates of amended plants by 40% as compared with controls. The digestate (D0.05% N) treatment significantly increased leaf P and K contents while decreasing leaf Ca, Fe and Mn contents. Digestate also increased some key soil enzyme activities of C, N, P and S metabolism by >10-fold compared with the control soil. In a phytomanagement scenario, digestate would be a preferred amendment resource for the production of clean birch leaf biomass on contaminated red gypsum landfill, as birch trees amended with digestate had lower leaf TE and higher leaf nutrient contents than control birches.

Recovery elemental sulfur from calcium sulfide prepared by red gypsum in sulfuric acid wastewater treatment

Recovery elemental sulfur from calcium sulfide prepared by red gypsum in sulfuric acid wastewater treatment

A Novel Approach for Separation and Recovery of Titanium, Scandium, Iron from Acidic Wastewater and Red Gypsum Utilization

A Novel Approach for Separation and Recovery of Titanium, Scandium, Iron from Acidic Wastewater and Red Gypsum Utilization

Influence of Carbon and Pyrite on Desulfurization Behavior of Red Gypsum at High Temperature

Influence of Carbon and Pyrite on Desulfurization Behavior of Red Gypsum at High Temperature

Nitrogen uptake and biochemical activity in maize rhizosphere during growth on acidic and neutralized soils

This work aimed to understand the effects of liming and no tillage on the pH stability and inorganic N uptake in the rhizosphere of maize plants on an acidic soil depleted in organic matter, reclaimed by liming and no tillage in a long-term field trial. We analyzed the inorganic N dynamics, respiration, microbial biomass and enzyme activities in the rhizosphere and bulk soil of maize plants grown in rhizoboxes on acidic soil under conventional tillage or no tillage management with or without liming and amendment (sugar beet foam and red gypsum). Analysis of inorganic N in the rhizosphere showed preferential NH4+-N uptake and reduced NO3−-N uptake by maize plant grown on acidic non tilled soil. With few exceptions, soil respiration, microbial biomass and enzyme activities were higher in the maize rhizosphere than in bulk soil. Soil respiration and enzyme activities were generally higher in the rhizosphere of non-tilled soils, whereas microbial biomass was higher in the rhizosphere of the amended soils. The study, based on rhizobox, showed effectiveness of sugar beet lime and red gypsum in the neutralization of the pH value in the rhizosphere during the early stages of maize growth, and the limited capacity of the plant to neutralize the acidic soil pH value in the rhizosphere of the non-amended soil. Positive interactive effects of tillage and liming were observed on the biochemical activity in the plant rhizosphere that could contribute to explain the positive effects of this management practice on the soil fertility observed at field scale on the long term.

A combined approach utilizing UAV 3D imaging methods, in-situ measurements, and laboratory experiments to assess water evaporation and trace element uptake by tree species growing in a red gypsum landfill

The extractive industry is increasingly faced with problems of managing contaminated sites. The red gypsum landfill at the Ochsenfeld site is representative of the typology byproduct storage of the Ti-extraction activity. The management of the elemental content and the water body are the issues at this site. The aim of this study was to evaluate the canopy conductance (gcmax) of various tree species and the content of elements in the leaves, utilizing the opportunity of a demonstration plantation setup in 2014 with sixteen tree species, combined with a growth chamber experiment. We combined the gas exchange measurements with the data from two multispectral cameras with RGB and NIR bands embarked on an unmanned aerial vehicle (UAV). In the field, Ostrya carpinifolia, Maclura pomifera, and Rhus copallina had the highest gcmax of all planted tree species, and the high transpiration rate in O. carpinifolia was confirmed in a pot-based controlled experiment. Except R. copallina, the species with a high Mn content (O. carpinifolia, Betula pendula, and Salix aquatica grandis) had high stomatal conductance. O. carpinifolia could therefore be a species to exploit in the management of landfill leachates, especially in the context of climate change since this species is well adapted to dry environments.

Efficient removal of iron from red gypsum via synergistic regulation of gypsum phase transformation and iron speciation

Red gypsum is a type of iron-rich gypsum residue originated from industrial titanium dioxide process using Ilmenite. Currently, it has a low rate of comprehensive utilization about 20%, and deep removal of iron impurity is the crucial factor that directly limits its multipurpose utilization. In this study, the iron was efficiently removed from red gypsum residue by synergistic controlling the phase transformation of gypsum and the iron speciation under hydrothermal conditions. The iron removal efficiency was more than 99% under the optimized treatment condition (i.e. liquid-solid ratio of 10, with 1.5 M HCl as mineralizer, heating at 140 °C for 6 h). The X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the phase transformation and crystal growth of gypsum accelerated by H+ was the essential reasons to fully remove iron. Moreover, H+ also provided acidic conditions (pH < 1) to change the iron speciation from amorphous oxide or hydroxide fine particles into soluble Fe3+ which release into the solution and easy to be removed by solid-liquid separation. In this work, based on the synergistic regulation of gypsum phase transformation and iron speciation, a feasible method for deep removal of iron from red gypsum was proposed, which is conducive to broadening the comprehensive utilization range of red gypsum. This work would inspire the treatment and resource utilization of industrial gypsum residues containing other contaminants or impurities, including heavy metals and organic matters.

A Review of the Commercial Uses of Sulphate Minerals from the Titanium Dioxide Pigment Industry: The Case of Huelva (Spain)

This study was focused on the historical evolution of the waste management policy carried out by the Spanish industry devoted to titanium dioxide pigments manufacturing for minimising its environmental impact. This challenge was achieved by modifying the original chemical process and converting the originally dissolved sulphate and sulphuric acid present in the final streams of the factory into sulphate minerals (melanterite FeSO4·7H2O, szomolnokite FeSO4·H2O, and gypsum CaSO4·2H2O). These by-products were physicochemically, mineralogically and radiologically characterised in order to gain basic information for its subsequent commercial use. Some of the uses summarised in this study for both ferrous sulphates are as a supplier of iron to prevent chlorosis, animal food, manufacture of cement (to reduce Cr VI), primary flocculants for ferrous sulphates, magnetite nanoparticle and nano-Fe2O3 formation, production of magnetite concentrate, remediation of polluted soils with metals, and treatment of wastewaters. Red gypsum was analysed as a substitute for natural gypsum in the manufacture of cement, construction materials, inhibitor in soil erosion, and the immobilisation of heavy metals in agricultural soils and carbonation processes.

Utilization of waste red gypsum in autoclaved aerated concrete preparation

In this study, the utilization feasibility of red gypsum (RG) as a substitute for fly ash to prepare the autoclaved aerated concrete (AAC) was examined. Influences of RG replacement ratio on the gas foaming, mineral components, morphology and mechanical properties were investigated. In addition, analyses of microstructure evolutions, phase compositions and thermal changes were carried out to explore the mechanism of strength improvement for AAC blocks. Results show that the replacement of fly ash by RG reduced the gas-foaming rate, which was resolved by Na2CO3 addition and it’s optimum dosage is 0.75%. The main phases in AAC are C-S-H gel, katoite, tobermorite and anhydrite. A proper amount of RG replacement (5%–20%) promoted the increase of relative strength of AAC samples. The synergistic enhancement of the anhydrite system and tobermorite system ensured an increase in relative strength. The optimum RG replacement ratio in AAC is 20%. With this substitution ratio, density can be obtained around 617 kg/m3 and compressive strength can reach about 4.2 MPa, which satisfies the requirements of B06, A3.5 grade in Chinese national standard GB 11968-2019.

Effect of compaction on physical properties of a sewage sludge and red gypsum mixture as intermediate landfill cover

This paper investigates the response of sewage sludge and red gypsum mixture under different compaction degree conditions in terms of hydraulic conductivity and unconfined compressive strength (UCS). The UCS and hydraulic conductivity assessments were undertaken using UCS machine and column test using the constant head method, respectively. Five samples were compacted to various degree of compaction (60, 70, 75, 80 and 85%) and percolated with distilled water for six months. The leachate samples from the column test were collected and analyzed at pre-determined days of 1, 3, 7, 14, 28, 42, 56, 75, 90, 120, 150 and 180. The UCS of samples increased with increasing degree of compaction, attributed to the increased number of contact and interparticle interaction between the particles. The degree of compaction appears to affect the initial hydraulic conductivity for the first three days of the experiment, however, gradually stabilize at 10-6 cm/s after 75 days for all samples. The concentration of leached metals and chemical oxygen demand (COD) is below the regulated limit that could affect the environment. The recommended degree of compaction is beyond 80% to achieve the required compressive strength of 345 kPa.

Synthesis of anhydrite from red gypsum and acidic wastewater treatment

One-step process of red gypsum leaching to produce anhydrite was proposed. The effects of sulfuric acid concentration, reaction temperature and reaction time on both the leaching rate of red gypsum, the phase and micro-morphology of the product were systematically investigated. The acid leaching solution was tried to use circularly. And the valuable components in the leaching solution were recovered by step precipitation. Anhydrous calcium sulfate powder with anhydrite crystal phase and smooth and serrate morphology was successfully produced. The leaching rate of red gypsum was 39.82% under optimized conditions. The optimum cycle number for the reuse of acid leaching solution was 5. Sulfate ions and iron ions in the leaching solution were recovered by adjusting the pH value. A preparation mechanism of anhydrite from red gypsum was also proposed by theoretical analysis. All of these indicated that the whole procedure setup showed potential application for red gypsum utilization.