Gypsum and high quality binders derived from water treatment sediments and spent sulfuric acid: Chemical engineering and environmental aspects

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Background: The re-use of waste is the most important aspect of sustainable development for human health and environmental protection. Millions of tons of hazardous spent sulfuric acid and lime mud are produced by water treatment facilities every year. Unlike other types of waste, lime mud can sometimes be used for the thermal regeneration of lime. However, this approach requires a high energy consumption and, thus, cannot be considered a sustainable or green process. Compared to the latest research, the method presented here allowed for the production of anhydrite in one step at very low temperatures and in a short time while also bypassing the stage of gypsum phase formation.Results: Calcium sulfate anhydrite was synthesized from the water treatment waste of lime mud by a low-temperature method at temperatures of 25 and 45 °С. The resulting samples were composed of anhydrite with different crystal morphologies. This was confirmed by XRD, DTA, SEM, TEM, and thermochemical calculations. Dependences of the influence of the shape of crystals on the main technological properties of anhydrite cement and the influence of additives on the activation of the binding properties were established. Conclusion:The research shows that different types of calcium sulfate anhydrite require different additives and in different amounts. Introducing the optimal composition of additives-activators made it possible to obtain anhydrite cement with a wateranhydrite ratio of 0.25, an onset of setting no earlier than 40 min, an end of setting no later than 12 h, and a strength of 28.8 MPa.

Section: Methodsmentioning

confidence: 99%

“…A detailed characterization of the waste derived from diluted sulfuric acid (55 wt.%) is given in the literature. 23…”

Section: Materials and Reagentsmentioning

confidence: 99%

Low energy synthesis of anhydrite cement from waste lime mud

Kamarou

Moskovskikh

Chan

et al. 2022

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“…The recycling of waste solves the problems of environmental protection and is an integral part of the circular economy and sustainable development. [1][2][3][4] Electric arc furnace (EAF) dust is a finely dispersed fraction containing mainly iron and zinc, and impurities of other elements. The phase composition is mainly in the form of zinc ferrite.…”

Section: Introductionmentioning

confidence: 99%

Direct reduced iron and zinc recovery from electric arc furnace dust

Мацукевич

Kulinich

Romanovski

2022

BACKGROUND At present, the volumes of use of electric arc furnace (EAF) dust are extremely insignificant. The volumes of their formation amount to thousands of tons per month. During storage, they have a negative impact on the environment. At the same time they are a material that has a valuable composition (oxides of iron, non‐ferrous metals, etc.) and is promising for recycling. However, the secondary use of zinc‐containing EAF dust in ferrous metallurgy leads to the accumulation of zinc in the lining of blast furnaces and frequent malfunctions. RESULTS It has been established that zinc oxide is mainly in the bound state in the composition of the franklinite phase (Zn,Mn,Fe)(Fe,Mn)2O4. The processes of solid‐phase reduction of EAF dust with the production of zinc concentrate and sponge iron, which are in demand as raw materials for non‐ferrous and ferrous metallurgy, have been studied. The optimal conditions for the reduction process were determined and the physicochemical characteristics, granulometric and phase composition of the initial materials, and reduction products were investigated. CONCLUSIONS It has been established that the use of a combination of reducing agents of different nature (coal coke and H2) during heat treatment at 1100 °C and cooling in a reducing medium (Ar/H2, 5 vol%) makes it possible to obtain sponge iron with impurities (the highest degree of iron metallization was 97.5%), and zinc oxide with a basic substance content of about 98.4 wt.%. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

“…Waste recycling is one of the most important challenges for green chemistry, circular economies and sustainable development. 1,2 Wastes are often used in the production of materials for various purposes: modified materials for water treatment, [3][4][5] wastewater treatment, 6,7 recovery of metals, 8 pigments 9,10 as well as building materials, such as gypsum, [11][12][13] anhydrite, 14,15 binders, 16 bricks, 17,18 composites, [19][20][21][22] etc.…”

Section: Introductionmentioning

confidence: 99%

Paper industry slag for the production of building ceramics

Zalyhina

Cheprasova

Romanovski

2022

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Background Re‐use of wastes as a part of sustainable development is one of the most important aspects of a healthy human life and environmental protection. This study examines the viability of using paper industry slag for the production of building ceramics. Results Paper industry slag was used in the production of ceramic bricks as a burnable additive in amounts of 5, 10 and 15 wt%. The slag was introduced without and after three different preparatory operations: dried, dried and ground, granulated and dried. Clay was used as a raw material and quartz sand as a lean additive. The samples were made by plastic molding. Drying was carried out at a temperature of 100 °C. To determine the optimal heat treatment temperature, firing was carried out at 900, 950, 1000 and 1050 °C with holding at the maximum temperature for 30 min, followed by determination of the properties of the samples. Conclusions It has been established that the samples obtained using the slag have good physical and mechanical properties and comply with current standards. At the same time, the use of slag in the production of ceramic bricks makes it possible to solve the problem of waste management, as well as to obtain a secondary material resource from the slag – a burnable additive, which leads to savings in raw materials and energy resources in the production of ceramic bricks. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).