High-purity Carbonate Research Articles

Adaptive fault diagnosis for high-purity carbonate process based on unsupervised and transfer learning

Reactive distillation integrates reaction and distillation to achieve process intensification. And the increasing process complexity urgently requires fault diagnosis system to ensure its safe and efficient operation. However, establishing fault diagnosis model is facing intractable challenges, e.g. scarce labeled data, operating mode changeover due to product proportion variation. To tackle absent labeled data problem, pseudo-labeled database is established by integrating data mining, density-based spatial clustering of applications with noise algorithm and process knowledge, based on which unsupervised deep learning is developed. Besides, to make intelligent fault diagnosis system adaptive for multimode operation changeover, transfer learning with domain adaptation strategy is adopted, which could mitigate different data distributions in various operating states and transfer knowledge learned from source domain to target domain. Taking carbonate ester process with reactive distillation as benchmark, the performance and superiority of unsupervised learning and transfer learning is verified and demonstrated in solving the corresponding puzzle.

Selective Lithium Recovery from Spent Lithium Manganate Batteries Using Oxidative Stabilization Technique.

Using oxidizing compounds to handle the recycling of discarded lithium batteries has advanced significantly in recent years. One of the most prominent methods is the sintered electrode powder treatment using pre-used additives, with an aqueous solution of the oxidizing agent fueling highly selective lithium extraction and transition metals retention in the refractory material. Herein, phosphoric acid (H3PO4) was used as the exchanger and hydrogen ions provider, the oxidant (K2S2O8) activity was driven by heating, the raw material structure was deformed and adjusted by the oxidizing drive, and lithium was exhausted, while manganese was converted into manganese(III) phosphate hydrate and manganese dioxide insoluble material. The optimized conditions resulted in a lithium leaching rate of 94.16 % and a separation factor of 95.74 %, while the corresponding manganese leaching rate was limited to less than 5 %. The X-ray diffraction, X-ray spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry measurements were used to investigate the influence of oxidation driving force and lithium leaching. Finally, the lithium leach solution was continuously stirred with sodium carbonate in boiling water to obtain the precipitate, which was separated and washed several times to obtain high-purity lithium carbonate.

Toward understandable semi-supervised learning fault diagnosis of chemical processes based on long short-term memory ladder autoencoder (LSTM-LAE) and self-attention (SA)

Fault diagnosis and localization play vital role in chemical process monitoring. Finding the root cause of fault accurately and timely is the key to avoid serious accidents and ensure process safety. Unfortunately, most deep learning-based models only involves in predicting fault state and interpretability is still not fully explored. Besides, lack of labeled samples in practical situations makes supervised learning difficult to implement. To circumvent the obstacle, semi-supervised learning based on long short-term memory ladder autoencoder is combined with self-attention mechanism, which is intended to establish interpretable model by explicitly clarifying the corresponding relationship between abnormal variables and faults. Using Tennessee Eastman process and practical high-purity carbonate production process as benchmark, fault diagnosis and identification performance of proposed LSTM-LAE-SA is validated, and interpretability analysis is performed to demonstrate its capabilities in abnormal variable locations. The developed understandable model could improve operator's trust and industrial application in fault diagnosis system.

Recovery of high-purity hydromagnesite from seawater through carbonation using Ca(OH)2

The economic challenges arising from resource depletion and uneven distribution of Mg in land reserves have spurred interest in technologies for Mg extraction from seawater. Thus, this study introduces a novel method to recover high-purity magnesium carbonate, specifically hydromagnesite, from seawater through carbonation using Ca(OH)₂ as an alkali source. A significant achievement of this method is the production of high-purity hydromagnesite despite the presence of large amounts of Ca, realized only through carbonation without the need for expensive additives such as NaOH. Experimental results reveal that the Ca(OH)₂ content predominantly influences the Mg dissolution efficiency during carbonation and the overall Mg recovery rate. Maximizing the efficiency of this technology relies on using an appropriate amount of Ca(OH)₂. Notably, the appropriate amount of OH− supply enhances CO₂ dissolution, facilitating Mg dissolution. Conversely, an excess of Ca(OH)₂ impedes Mg dissolution. The overall Mg recovery rate reaches a peak of 67 %, enabling the recovery of 3.4 kg of hydromagnesite from one ton of seawater. The findings highlight the effectiveness of the proposed technology as a promising and cost-effective method for extracting high-purity Mg from seawater, utilizing Ca(OH)2, previously considered an impurity, as a cost-effective alkali source.

Synthesis of nano-calcium carbonate from waste cement and techno-economic and environmental evaluation

Mineral carbonation stands out not only as an effective method for reducing CO2 emissions but also as a strategic approach to upcycling industrial waste. This study introduces a novel procedure for generating high-purity nano-calcium carbonate (nCaCO3) from waste cement powder, deploying hydrochloric acid (HCl), and sodium hydroxide (NaOH), both obtained through the electrolysis of sodium chloride (NaCl). Our approach, aimed at both environmental preservation and techno-economic feasibility, encompasses optimizing calcium extraction conditions through rigorous analysis of variables such as HCl concentration, solid-to-liquid ratio, and reaction temperature, subsequently proposing a rate law for the extraction process. Furthermore, the method emphasizes the production of high-purity CaCO3 by meticulously removing metallic impurities from the extracted solution with 1.0 M NaOH, culminating in pure calcium hydroxide and the generation of nCaCO3 particles with superior purity (>99 %) and a uniform particle size (80–140 nm). An exhaustive environmental and economic assessment indicates that our process, while consuming varying energy levels based on operational potentials, anticipates a significant reduction in CO2 emissions by 46.1 %, alongside a competitive production cost (335 USD/ton of nCaCO3), thereby demonstrating substantial advantages over traditional methods in terms of sustainability, efficiency, and cost-effectiveness.

Experimental study on indirect mineral carbonation using five types of slag for production of high-purity calcium carbonate

Experimental study on indirect mineral carbonation using five types of slag for production of high-purity calcium carbonate

Effects of vaterite and leachate solid residue prepared from magnesium slag on the performance of cement mortar

This study introduces a "leaching-carbonation" method for converting magnesium slag (MS) into two valuable byproducts: high-purity spherical vaterite calcium carbonate (VCC) derived from the carbonation of filtrate and leached solid residue (LSR) rich in amorphous silica gel. The investigation delves into the performance and microstructure of cement incorporating MS, VCC, and LSR. Results indicated that MS and LSR decreased the flowability of cement mortar, while VCC significantly enhanced it compared to the control sample. MS negatively affected compressive strength and water absorption, whereas LSR and VCC improved both aspects in comparison to MS. Although MS, LSR and VCC shortened induction period of cement paste, both LSR and VCC improved the cumulative heat release compared to the control sample. Additionally, a new hydration product, monocarbonate, was formed in the VCC sample. The presence of amorphous silica gel in LSR exhibited pozzolanic reactivity and could react with Ca(OH)2 to form C-S-H gel. Furthermore, both LSR and VCC samples exhibited a refined pore size distribution compared to the control and MS samples. In summary, the obtained results offer a promising technology for maximization of the valuable utilization of MS.

Use of spent fluid catalytic cracking catalyst (FCC) in Limestone Calcined Clay Cement (LC3) systems: Studies in pastes and mortars

This study evaluates the substitution of calcined clay for a waste from the petrochemical industry, spent fluid catalytic cracking catalyst (FCC), as a source of reactive aluminosilicates in Limestone Calcined Clay Cements (LC3) systems. Three carbonate types were used to make cement-type LC3: a high-purity calcium carbonate, waste from the marble industry, and another from a dolomite soil source. LC3 blends were prepared by mixing 50 wt% OPC, 5 wt% calcium sulfate dihydrate, 30 wt% FCC and 15 wt% from each carbonate source. A mixture than substituting the carbonate source for a siliceous source was prepared to analyse the influence of carbonate phases in LC3 systems. The hydration process of the LC3 blends was studied by X-ray diffraction, thermogravimetric analyses, isothermal calorimetry and FESEM. Mechanical properties were studied by measuring compressive strength at 7, 28 and 90 days. The obtained results corroborated that the mortars prepared with LC3 cements using the FCC obtained higher compressive strength than the control mortar prepared with ordinary Portland cement (OPC) at 28 and 90 curing days. It has been demonstrated that FCC is a by-product that can substitute calcined clay, and the different sources of carbonates such as high purity, waste or contaminated with magnesium do not interfere with the performance of this type of cement.

Indirect mineral carbonation of recycled concrete aggregate: Enhancing calcium extraction using a packed bed reactor

Mineral carbonation of industrial residues is gaining increasing interest, with the first pilot and industrial-scale applications being implemented. The process offers a low-risk, easily available solution for permanent carbon dioxide storage while concurrently valorising industrial wastes. This work investigates the indirect mineral carbonation of recycled concrete aggregate (RCA), in which calcium is first leached from the RCA into an aqueous ammonium nitrate (AN) solution, followed by carbonation to yield high-purity precipitated calcium carbonate. The study focuses on the first step, calcium dissolution, which traditionally takes place in a stirred batch reactor (SBR). However, SBRs often encounter solubility constraints, leading to low calcium extraction yields. In this investigation, we explore the application of a packed bed reactor (PBR) and demonstrate its superior performance, resulting in a calcium extraction enhancement of 27% to 55% relative to SBRs, across AN concentrations ranging from 0.25 to 2.0 mol/kg, at 25 °C and atmospheric pressure. The PBR’s superior performance can be attributed to the more compact design, enabling longer dissolution times, and to the continuous supply of fresh solvent, effectively reducing solubility limitations. The impact of key operating parameters (AN concentration, liquid flow rate and extraction time) are systemically assessed experimentally, accurately modelled using a shrinking-core model, and illustrated in process performance maps. Furthermore, this research highlights the significance of ammonium nitrate recovery from the wet solids after filtration to ensure the process’s environmental viability. The packed bed reactor (PBR) functions as an integrated filter, facilitating the straightforward recovery of 80% of the trapped ammonium nitrate solution through simple water flushing. In conclusion, the utilisation of PBRs in indirect mineral carbonation presents an innovative and efficient approach for enhancing calcium extraction while addressing environmental concerns through ammonium nitrate recovery. The applicability of PBRs extends beyond recycled concrete aggregates, and could also be successfully applied for other coarse industrial residues such as steel slags.

Recovery of lithium resources from salt lake brines using a novel low dissolution loss extractant of DEHEHP with FeCl3

Lithium is becoming one of the most eye-catching metal elements in modern industry, mainly because of its crucial role in manufacturing lithium-ion batteries. The demand for lithium in the new energy market is burgeoning significantly, while enormous lithium resources reserved in salt lakes in northwest China are not exploited effectively, due to the high Mg/Li mass ratio. Although the TBP extraction system has been applied in lithium extraction from salt lake brines, there are still some problems to be solved, such as its high solubility, easy degradation, and so on. In this work, a novel low dissolution loss extraction system was developed, with DEHEHP and FeCl3 serving as extractant and co-extractant, respectively. A real brine from Da Qaidam Lake was used to prove its practicality and effectiveness. After studying the detailed conditions of each process, a whole countercurrent process was performed, including eight stages of extraction, two stages of scrubbing, three stages of stripping, and regeneration. It was found that 99.4% of Li+ was successfully recovered from the brine, and the stripping liquor contained 22.74 g/L Li+, 0.51 g/L Mg2+, and 3.16 g/L B. The concentration of Li+ increased approximately 20-fold while the Mg/Li mass ratio decreased by a factor of 3900, from real brine to stripping liquor. High-purity (>98.5%) lithium carbonate products were prepared from the stripping liquor by precipitation. The dissolution loss of the organic phase in the raffinate was only 22.5 ppm, much lower than published works. Finally, the mechanism of extraction and co-extraction were systematically studied and the structure of the complex formed during extraction was revealed as LiFeCl4·2DEHEHP.

Advanced Lithium Extraction Membranes Derived from Tagged-Modification of Polyamide Networks.

Efficient Mg2+ /Li+ separation is crucial to combating the lithium shortage worldwide, yet current nanofiltration membranes suffer from low efficacy and/or poor scalability, because desirable properties of membranes are entangled and there is a trade-off. This work reports a "tagged-modification" approach to tackle the challenge. A mixture of 3-bromo-trimethylpropan-1-aminium bromide (E1 ) and 3-aminopropyltrimethylazanium (E2 ) was designed to modify polyethylenimine - trimesoyl chloride (PEI-TMC) membranes. E1 and E2 reacted with the PEI and TMC, respectively, and thus, the membrane properties (hydrophilicity, pore sizes, charge) were untangled and intensified simultaneously. The permeance (34.3 L m-2 h-1 bar-1 ) and Mg2+ /Li+ selectivity (23.2) of the modified membranes are about 4 times and 2 times higher than the pristine membrane, and they remain stable in a 30-days test. The permeance is the highest among all analogous nanofiltration membranes. The tagged-modification method enables the preparation of large-area membranes and modules that produce high-purity lithium carbonate (Li2 CO3 ) from simulated brine.

Optimal design, intelligent fuzzy logic and model predictive control for high-purity ethyl-methyl carbonate and diethyl carbonate production using reactive dividing wall column

Methyl carbonate (EMC) and Diethyl carbonate (DEC), as excellent solvents for lithium-ion electrolytes, are synthesized by transesterification, and consecutive reaction seriously complicate optimization and control issues. Process synthesis, parameters optimization and advanced control are crucial points that should be addressed for this ill-conditioned and highly nonlinear system, which is the motivation and novelty of present work. With single-objective and multi-objective genetic algorithm, intensified processes for EMC and DEC production were optimized respectively with heterogeneous catalyst. And reactive dividing wall column achieved 23% and 13% total annualized cost reductions compared with reactive distillation for two target carbonates. Based on optimal steady-state solution, intelligent fuzzy logic and model predictive control of EMC and DEC production is conducted to clarify their respective strengths in intensified process with consecutive reaction. Sequential optimization for parameters of FLC was carried out with Integral of Squared Error (ISE) as objective. Finally, control performance of FLC and LPMC are compared with that under PID control, and results show that overshoot and transition time under FLC and LMPC are obviously mitigated, along with evident reduction in ISE.

Selective leaching process for efficient and rapid recycling of spent lithium iron phosphate batteries.

With the continuous development of new energy vehicles, the number of decommissioned lithium iron phosphate (LiFePO4) batteries has been constantly increasing. Therefore, it is necessary to recover metal from spent LiFePO4 batteries due to the high potential for environmental protection and high resource value. In this study, sodium persulfate (Na2S2O8) was selected as the oxidant to regulate and control the oxidation state and proton activity of the leaching solution through its high oxidizing ability. Selective recovery of lithium from LiFePO4 batteries was achieved by oxidizing LiFePO4 to iron phosphate (FePO4) during the leaching process. This paper reports an extensive investigation of the effects of various factors, including the acid concentration, initial volume fraction of the oxidant, reaction temperature, solid-liquid ratio, and reaction time, on lithium leaching. Li+ reached a high leaching rate of 93.3% within 5 minutes even at a low concentration of sulphuric acid (H2SO4), and high-purity lithium carbonate (Li2CO3) was obtained through impurity removal and precipitation reactions. In addition, the leaching mechanism was analysed by both X-ray diffraction and X-ray photoelectron spectroscopy characterization. The results show that the obtained high lithium-ion (Li+) leaching efficiency and fast Li+ leaching time can be ascribed to the superior oxidizing properties of Na2S2O8 and the stability of the crystal structure of LiFePO4 during the oxidative leaching process. The adopted method has significant advantages in terms of safety, efficiency and environmental protection, which are conducive to the sustainable development of lithium batteries.

High-purity Lithium Carbonate Manufacturing Technology from the Secondary Battery Recycling Waste using D2EHPA + TBP Solvent

리튬이온 배터리(LIB) 제조를 위한 리튬의 사용이 점차 증가함에 따라 그에 따라 발생되는 리튬이온배터리 폐기가 증가될 것으로 사료된다. 이에 따라 폐배터리를 재활용을 하기위한 용매 추출을 통한 재활용에 대한 활발한 연구가 니켈, 코발트 및 망간과 같은 유가금속을 제거한 후 얻은 폐 용액에서 리튬의 회수가 중요하다. 본 연구에서는 폐이차전지 재활용공정 후 발생되는 폐액에서 리튬을 회수하기위해 추출제 Di-(2-ethylhexyl)phosphoricacid(D2EHPA)와 등유의 개질제 Tri-n-butyphosphate(TBP)를 선택적으로 혼합하여 추출조건을 최적화하였다. 폐액에는 리튬과 고농도의 나트륨(Li+ = 0.5% ~ 1%, Na+ = 3 ~ 6.5%)을 함유하고 있었으며, 리튬의 추출은 유기용매의 다른 구성에서 최종적으로 20% D2EHPA + 20% TBP + 60% 등유로 구성된 유기용매에서 효과적인 추출을 조건을 확립하였다. NaOH의 비누화를 이용한 SX 시스템에서는 평형 pH 4~4.5에서 유기 대 수성(O/A)이 5일 때 약 95% 이상의 리튬이 선택적으로 추출되는 것을 확인하였다. 적은 양의 나트륨으로 염화리튬에서 탄산리튬 분말을 얻기 위해 고순도 중탄산암모늄을 처리하였다. 최종적으로 처리된 탄산리튬에 여러번 세수를 통하여 미량의 나트륨을 제거하고 고순도 탄산리튬 분말(순도 99.2%)을 제조하였다. 따라서 본 연구를 통하여 폐이차전지 재활용공정에서 발생되는 폐액을 활용하여 탄산리튬의 효율적인 제조방법을 확인하였다.

Kinetics measurement of ethylene-carbonate synthesis via a fast transesterification by microreactors

High-purity ethylene carbonate (EC) is widely used as battery electrolyte, polycarbonate monomer, organic intermediate, and so on. An economical and sustainable route to synthesize high-purity ethylene carbonate (EC) via the transesterification of dimethyl carbonate (DMC) with ethylene glycol (EG) is provided in this work. However, this reaction is so fast that the reaction kinetics, which is essential for the industrial design, is hard to get by the traditional measuring method. In this work, an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst. The effects of flow rate, microreactor diameter, catalyst concentration, reaction temperature, and reactant molar ratio were investigated. An activity-based pseudo-homogeneous kinetic model, which considered the non-ideal properties of reaction system, was established to describe the transesterification of DMC with EG. Detailed kinetics data were collected in the first 5 min. Using these data, the parameters of the kinetic model were correlated with the maximum average error of 11.19%. Using this kinetic model, the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%, suggesting its satisfactory prediction performance.

Preparation of high-purity lead carbonate and lead oxide from spent lead paste

Compared with pyrometallurgical recycling, hydrometallurgical recycling of spent lead paste has obvious advantages such as energy saving and emission reduction, however, hydrometallurgical recycling of spent lead paste is also characterized by high levels of impurities (e.g.,Fe, Ba and Cu) in the recovered products. In this study, a green process for the conversion of spent lead paste into high-purity lead carbonate is presented. The process consists of four steps: sulfation, desulfurization leaching, distillation and carbonization to obtain high-purity lead carbonate. The details are as follows: (1) Spent lead paste (mainly composed of lead sulfate, lead dioxide, lead oxide and lead monomers) was converted into sulfated lead paste using sulfuric acid, hydrogen peroxide and sodium chloride. (2) The sulfated lead paste was reacted with ammonium acetate to leach the lead while desulfurizing; the leaching rate was reached 99.94% under the conditions of 30 wt% ammonium acetate concentration, 40 °C reaction temperature and 7.5 min reaction time. (3) Glycerol was added to the mother liquor and distilled to obtain a glycerol solution containing lead acetate. (4) Using ammonium carbonate (aq) as a carbonizing agent, reacting for 20 min under the condition that the molar ratio of CO32−/Pb is 1.10 can make more than 99.9% of lead precipitate to obtain high-purity lead carbonate products. (5) The lead carbonate product decomposed into orthorhombic α-PbO at 350 °C. (6) Recovered lead oxide product has better electrochemical performance than commercial lead oxide. This process prepares high-purity lead carbonate and lead oxide products with reduced energy consumption and recycles the spent lead paste. This study provides a feasible technology for green recycling of spent lead paste.

Preparation of High-Purity Lead Carbonate from Spent Lead Paste

Preparation of High-Purity Lead Carbonate from Spent Lead Paste

Self-Healing Behaviors of Core–Shell-Structured Microcapsules Cement-Based Materials Immobilized with Microbes by Expanded Perlite

To improve the weather resistance of Bacillus mucilaginous L3 in cement-based materials, we used the expanded perlite as an immobilization carrier of B. mucilaginous L3, and prepared core–shell-structured microcapsules using a metakaolin-sodium silicate mixed solution as the coating shell. Such immobilization by microcapsules can ensure the high weather resistance of B. mucilaginous L3 in cement-based materials, and was characterized by relevant methods. The cement-based materials containing self-healing microcapsules demonstrated high weather resistance, and can heal the largest cracks width of 0.85 mm. The expanded perlite offered the microbes with attachment sites and a survival and protection space. The self-healing grains coated with high-activity metakaolin can contact well with the substrate in the concrete, which showed excellent integrity. The minerals separated out by the self-healing microbes were high-purity calcite-like calcium carbonate and exhibited high healing ability.

Simple recycling of biowaste eggshells to various calcium phosphates for specific industries

Egg consumption is very high throughout the world and with it comes enormous amount of waste eggshells. To reduce and utilize these wastes, eggshell wastes were simply transformed to low- or high-purity calcium carbonate grades by washing, crushing, and drying to use as raw materials for producing highly valuable calcium phosphate products. Low-purity calcium carbonate grade was used to prepare triple superphosphate for using in fertilizer industry, whereas high-purity calcium carbonate grade was used to produce dicalcium phosphate dihydrate, monocalcium phosphate monohydrate, and tricalcium phosphate for using in mineral feed and food additive industries. All calcium phosphate samples obtained by simple, rapid, cheap, and environmentally safe method using eggshells and phosphoric acid were identified and their structural phases and impurities were determined by XRF, XRD and FTIR techniques. Thermal behaviors of raw materials and the prepared calcium phosphates excepted tricalcium phosphate were investigated by TG/DTG techniques. The methodologies described here will be useful to manage eggshells by converting them to highly valuable products, which can solve eggshell wastes problem from industries and communities. This finding supports the viewpoint of zero waste operation to produce value-added products for obtaining sustainable development, which may be selected as an alternative way for material recycling and waste management in the future.

Facile synthesis of pure vaterite using steamed ammonia liquid waste and ammonium carbonate without additives via simple mechanical mixing

This paper describes a simple, low-cost, and fast method for synthesizing high-purity porous vaterite calcium carbonate (CaCO3) without any additives using steamed ammonia liquid waste and (NH4)2CO3. The obtained vaterite samples were characterized using various techniques such as powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and laser particle size analysis (LPSA). The XRD and FTIR analyses indicate that the prepared product is high-purity vaterite CaCO3. The SEM analysis shows obtained micro/nanosized spherical and porous vaterites. The effects of stirring mode and stirring speed on the morphology, particle size, and stability of vaterite were studied systematically. The stirring speed and stirring mode were found to play an important role in the crystallization of vaterite CaCO3 with different purities, morphologies, particle sizes, and particle size distributions. Based on the analysis of vaterite CaCO3 particles obtained under different stirring modes and stirring speeds, a possible mechanism for obtaining smaller vaterite CaCO3 particles at high stirring speed is proposed. The possible mechanism underlying the properties of ammonia-distilled waste liquid during vaterite formation is also discussed.