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Recently, Luffa cylindrica has been drawing lots of attention in adsorption applications. However, the contaminated biomass needs to be properly disposed. Pyrolysis is a process capable of turning this type of residue into valuable product. Luffa cylindrica pyrolysis produces biochar which has been used as adsorbent for various cationic and organic species. Additionally, the use of solar power to heat the reactor reduces the environmental impact of pyrolysis. In this work, a lab scale solar pyrolizer was built in a 40-dollar budget. This biomass was previously submitted to slow pyrolysis in an electrical reactor at various temperatures (300, 400, and 500 °C) and heating rates (2, 10, and 20 °C.min-1) to access the influence of these parameters on biochar properties. Further, the Luffa sponge sample was submitted to solar pyrolysis. The characterization methods of TG/DTG, FTIR, SEM, and HHV analysis were employed to access biochar properties. Biochar adsorption performance was accessed by iodine adsorption experiments. Highest HHV (29,3 MJ.kg-1) was obtained for the biochar from the 500 °C, 2 °C.min-1 pyrolysis. Maximum iodine adsorption (162,9 mg.g-1) was observed on the biochar produced at 400°C, 2 °C.min-1. Solar biochar had a 24,3 MJ.kg-1 HHV and a Iodine adsorption of 115.2 mg.g-1.

In this innovative study, biogas has been associated with calcium carbonate [CaCO

Soil-cement bricks are earth construction materials that have been gaining prominence due to their environmental advantages. The Brazilian Technical Standard NBR 8491 establishes physical and mechanical procedures to characterize these bricks. However, the thermal characterization is an important assessment, since it is related to the building’s thermal performance. The objective of this study is to thermally characterize a panel of soil-cement bricks produced with mining tailings. For such, its absorptance (α) was evaluated using the ALTA II spectrometer, and its thermal transmittance (U) and thermal resistance (RT) through the hot box method (ISO 9869). The results enabled the calculation of the thermal capacity (CT), thermal lag (φ) and solar factor (FSO) of the panel, which were compared to the Brazilian Technical Standards NBR 15575-4 and NBR 15220 for Bioclimatic Zone 8. As a result, the soil-cement body panel showed values of α = 0.71, U = 2.47 Wm-2K-1, CT = 273.4 kJm-2K-1, φ = 6.02 h and FSO = 6.81%, meeting the requirements established in the first standard, but failing to attend the second. To comply with the Brazilians specifications, it is suggested to paint bricks with lighter colors focusing on decreasing its absorptance value. Thus, soil-cement bricks may be an environmental alternative to dispose of the waste generated during the mining process, contributing to sustainability.

The kinetics of atmospheric sulfuric acid leaching from a Brazilian nickel laterite ore was assessed using distinct reducing agents and ore mineralogy. This transitional ore contains 1.63% Ni distributed as 1.27% in coarse size (− 500 + 150 μm), mainly as silicates (lizardite and chlorite — 28.6%), and 2.06% in the fines fraction (− 75 μm), mainly as iron oxy-hydroxides (goethite and hematite — 49%). The effects of temperature, acid concentration, reducing reagent type, and concentration were evaluated. The − 75 μm fraction limited the leaching efficiency and the use of reducing media with thiosulfate improved leaching and Ni-Fe selectivity. However, at constant Eh of 626–743 mV and a pH range between 0.2 and 1.1, no substantial rise in metals extraction, except for Co and Mn, has been observed. In order to determine the process control at 95 °C, two regions in the extraction curves were used in combination with the shrinking core model. Control by porous diffusion was observed and the kinetic constant was found to be in the order kFe

Resumo: A glauconita (K₂(MgFe)₂Al₆(Si₄O₁₀)₃(OH)₁₂) é um mineral monoclínico, de cor verde, filossilicato hidratado de potássio e ferro. É uma fonte alternativa de potássio. Este trabalho investigou a dissolução de potássio em uma solução de ácido cítrico 2% (m/m) após prévio processamento térmico e químico, com aditivos (CaCO₃, MgCl₂.6H₂O), da rocha contendo glauconita, em seis temperaturas: 660°C, 700°C, 740°C, 780°C, 820°C e 860°C, 60 minutos e granulometria menor que 0,15mm. A relação mássica (rocha, CaCO₃, MgCl₂.6H₂O) foi: (1,0:0,2:0,3). Para este objetivo, foi selecionada uma rocha contendo glauconita da região de Cedro do Abaeté – MG, teor de 11,9% de K₂O e 58% de glauconita. A avaliação da extração de potássio foi por extração em solução de ácido cítrico 2% (m/m), temperatura de 95°C, durante 15 minutos. A maior extração de potássio foi de 78% na temperatura de 770°C. A curva passa por um máximo (770°C), mostrando que há um limite para a temperatura no processamento térmico. Acima deste valor há uma queda na extração indicando mecanismo diferente de reação entre a rocha e aditivos. Considerando o intervalo até 770°C, o processamento térmico torna o minério do Verdete uma potencial fonte alternativa de potássio para produção de fertilizante de liberação lenta. Palavras-Chave: Potássio; Verdete; Processamento Térmico; Glauconita. Abstract

Sources of fluoride contaminated water are found around the world and their treatment is required before human consumption. This paper contributes to advances in the use of bone-char as an adsorbent for fluoride, associating steps of chemical regeneration and fluoride adsorption in continuous systems, thereby making feasible the multiple use of the adsorbent. Following the development of low cost treatment of water defluoridation in a fixed bed column, using bone-char, regeneration was carried out with NaOH (0.5 mol/L) solution in subsequent adsorption/desorption cycles. The continuous system was modeled applying Thomas, Yoon-Nelson, Adams-Bohart, Wolborska and Yan models, and the Yan model showed the best adjustment. The adsorption capacity of 6.28 mg/g was obtained from the breakthrough curve. Chemical regeneration of bone-char was feasible, and a reduction in adsorption capacity of 30% was observed only after five adsorption/desorption cycles. Fontes de água contaminada com flúor são encontradas em todo o mundo e seu tratamento é necessário antes do consumo humano. Este artigo contribui para avanços no uso do carvão de osso como adsorvente para flúor, associando etapas de regeneração química e adsorção de flúor em sistemas contínuos, viabilizando o uso múltiplo do adsorvente. Seguindo o desenvolvimento do tratamento de água de baixo custo defluoretação em coluna de leito fixo, utilizando-se osso-char, a regeneração foi realizada com NaOH (0,5 mol/L) solução em ciclos de adsorção/dessorção subsequentes. O sistema contínuo foi modelado aplicando Thomas, Os modelos Yoon-Nelson, Adams-Bohart, Wolborska e Yan, e o modelo Yan apresentaram o melhor ajuste. o a capacidade de adsorção de 6,28 mg/g foi obtida a partir da curva de ruptura. Regeneração química de osso-char foi viável, e uma redução na capacidade de adsorção de 30% foi observada somente após cinco ciclos.

RESUMO A economia circular na mineração, com a utilização de rejeitos para geração de novos produtos, destaca-se como forma potencial de mitigar o passivo ambiental da atividade mineral. Este trabalho avaliou a utilização de rejeito da mineração de ouro, como matéria-prima principal, na composição de tijolos tipo solo-cimento. Para tal, foram preparadas misturas com traços cimento CPII-Z-32 (1): rejeito (5-10): solo (0-5) e submetidas à caracterização física (distribuição granulométrica pela NBR 7181, massa específica por picnometria a gás hélio e área superficial específica por BET), química (fluorescência de raios-X), mineralógica (difração de raios-X), geotécnica (limites de consistência) e ensaios de compactação (NBR 12023), sendo este último ensaio determinador do teor de umidade ótimo utilizado na produção dos tijolos para cada mistura. Os parâmetros mecânicos dos tijolos foram caracterizados segundo a NBR 8491 e a avaliação ambiental foi realizada através da NBR 10004. Os tijolos com traço 1:5:5 alcançaram resistência a compressão de 3,1 MPa e absorção de água de 17,0%, compatíveis com a exigência da norma. A NBR 10004 classificou estes tijolos como um produto não perigoso e não inerte devido à solubilização de alumínio superior ao limite estabelecido. A liberação de alumínio está associada a composição química natural das matérias-primas. Por outro lado, contaminantes do rejeito, como o cianeto, foram imobilizados pela mistura cimento, rejeito e solo através das fases de hidratação do cimento (C-S-H e C-A-S-H). Portanto, os estudos demonstraram que o rejeito da mineração de ouro estudada, até então considerado passivo ambiental, apresenta potencial para produção de tijolos tipo solo-cimento atendendo as especificações técnicas e ambientais.

In the face of water scarcity and more strict environmental regulation, water treatment is a demand and reuse is being encouraged in diverse production processes. Advanced treatments, such ...

Glauconite (K,Na) (Fe,Al,Mg) 2 (Si,Al) 4 O 10 (OH) 2 is a green, potassium and iron hydrated phyllosilicate, monoclinic mineral. It is a secondary mineral formed from the alteration of iron-rich micas, such as biotite. It is a potential source of potassium, but still not commercialized due to lack of commercial technology that makes the business viable. The objective of this work was to evaluate the reactivity, in relation to the release of potassium, from a glauconite-containing rock, subjected to thermal alteration, with additives, at two temperatures: 800°C &900°C. The source of glauconite was the Verdete that occurs in Serra da Saudade, in the region of the municipality of Cedro de Abaete, state of Minas Gerais, Brazil. The following additives were used:CaSO 4 .2H 2 O, CaCO 3 and Na 2 SO 4 ,at the mass ratio with respect to the rock: (1.0: 0.2: 0.3: 0.2). Thermal alteration was performed at 800°C&900°C. After thermal alteration, the calcined samples were leached with 20% sulfuric acid (m/m). The final product was a solution containing K 2 SO 4 . At the temperature of 800°C, the potassium released reached only 11.2%. Increasing the temperature to 900°C, the extraction incresed to 40%. There was a tendency for increased potassium release at temperatures higher than 900°C. These findings highlight gave the potential forglauconite to be exploited as an alternative source of potassium for the production of fertilizer, by thermal processing with sulfating compounds.

Nesquehonite is an attractive magnesium precipitation product as it sequesters CO2 and exhibits good filterability. Upon calcination, high-quality reactive magnesia is produced. As part of the hydrometallurgical processing of nickel, magnesia is used as a precipitating agent to recover nickel and cobalt in the form of a Mixed Hydroxide Precipitate (MHP). However, a waste solution with elevated concentration of magnesium is formed which can be an environmental liability. Chemical thermodynamic equilibrium modeling of magnesium carbonate precipitation from magnesium sulfate liquor predicted a high reaction extent of 99% could be achieved. Magnesium carbonate precipitation experiments were carried out by gradually mixing sodium carbonate solution and synthetic industrial liquor in a batch reactor at 25 °C, while monitoring solution concentrations and pH, used to estimate the supersaturation index. Calcination of the resulting solid at temperatures ranging from 450 to 650 °C produced magnesia with acetic acid activities ranging from 14 s to 41 s. The most reactive magnesia was obtained at the lower temperature of 450 °C with an activity of 14.7 ± 0.6 s, which meets industrial product specifications. Periclase was identified as the dominant magnesia mineral phase along with thenardite as a minor component.

In a scenario of hydric scarcity, water reuse is essential to minimize make-up; however, increased salinity comes along with recycling streams. Crystallization has been evaluated to remove dissolved ions; nevertheless, contaminants affect its efficiency. In this context, the removal of residual organics from the saline concentrate from electrodialysis applied for water reuse in a Brazilian petroleum refinery was investigated. Aiming at establishing a sustainable virtuous circle, bone char, a waste from food industry, 0.5–1.4 mm particle size, was used as adsorbent for refractory organics removal. Equilibrium adsorption time of 4 h was determined from batch experiments (through 72 h, at 25.0 ± 0.1 °C, pH 7.6 ± 0.5 and 200 ± 1 rpm, solid/liquid ratio of 10 g kg−1) in a shaker and a removal of 54% for dissolved chemical oxygen demand (COD) was observed. Adsorption kinetics (pseudo-first and pseudo-second order; Elovich equation) and equilibrium isotherms were evaluated. Pseudo-second order model for kinetics (R2 = 0.9993; k2 = 0.0184 mg−1 min−1; qe = 3.21 mg g−1) and Freundlich isotherm model best fitted to experimental data (R2 = 0.995), suggesting physisorption in multiple layers. The adsorbent thermal regeneration was evaluated (at 300, 500 and 700 °C, for 60, 120 and 180 min). Partial thermal regeneration was achieved at lower temperature and time demands (300 °C and 60 min—dissolved COD removal was around 40% after the first cycle of regeneration). Further investigation, including scaling-up and a cost-benefit analysis, is necessary in order to assess its use as a viable low-cost alternative for this type of effluent.

The presence of impurities in solution during crystallization can influence the crystallization kinetics of the desired product. Consequently, this affects the product quality parameters such as the crystal size distribution (CSD), purity, and morphology. This paper focuses on the application of eutectic freeze crystallization (EFC) to the purification of petrochemical brine rich in sulfate salts. The effect of phenol on the CSD, nucleation and growth rates, purity, and morphology of ice and sodium sulfate decahydrate crystals was evaluated using a batch EFC setup. Nucleation and growth rates were obtained from in situ image acquisition and analyses. In the presence of 0.2 wt % phenol, larger crystals were obtained for both ice and sodium sulfate decahydrate due to increased growth rates and reduced nucleation rates. The crystal habit of both ice and salt was not modified by the phenol impurity. Ice crystals presented elongated disk shapes and dendritic habit, and crystal sizes up to 1000 μm were obtained...

Water reuse in industrial processes has been an increasing need encouraged in recent years. However, as the streams are recycled, solutes accumulate, thus requiring purification techniques. Membrane processes (reverse osmosis and electrodialysis) have been implemented and in order to increase the reuse of water at its highest level, crystallization has been evaluated to remove salts from the concentrate produced and get a feasible disposal. Nevertheless, contaminants affect the crystallization performance, thus making the removal of residual organics important for both the efficiency of crystallization and the increase of water reuse. In this context, aiming at establishing a sustainable virtuous circle, bone char (0.5-1.4 mm particle size, mesoporous structure) was used to remove refractory organics from an electrodialysis concentrate effluent (C-EDR) from a Brazilian petroleum refinery, at a lab-scale, in a fixed-bed adsorption column. Bone char selectively and partially removed the refractory organics, a complex mixture of long-chain hydrocarbons, aromatic compounds, carboxylic acids, amines and amides. The maximum adsorption capacity increased with the increase in bed depth and reduction in flow rate. A maximum removal of 35.60 mg g

A thermal regeneration process of bone char (BC), used in fluoride adsorption, was investigated in this study. Adsorption experiments and solids characterization by Scanning Electron Microscopy (SEM), X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman Spectrometry were performed in order to get an insight about the physical and chemical transformations. The results show the evidence that there was diffusion of fluoride ions into bone char particles during thermal regeneration process. In addition, the formation of fluoridated hydroxyapatite is also observed showing that fluoride has been incorporated into the hydroxyapatite structure present in bone char, clarifying the mechanisms of thermal regeneration. In addition, it was observed that the heat (thermal) treatment could increase the degree of crystallinity of bone char. The adsorptive process of fluoride in bone char was fitted to pseudo second order kinetic model and was well represented by Freundlich, Redlich-Peterson and Sips isotherm models, pointing out the prevalence of chemical adsorption and formation of heterogeneous layers on the bone char surface. The results also indicated that the optimum temperature for thermal regeneration was 400 °C.

Chemical fertilizers, such as potassium chloride, ammonium nitrate and other chemical products like sodium hydroxide and soda ash are produced from electrolyte solutions or brines with a high content of soluble salts. Some of these products are manufactured by fractional crystallization, when several salts are separated as solid phases with high purity (>90%). Due to the large global demand for potassium fertilizers, a good knowledge about the compositions of salts and brines is helpful to design an effective process. A thermodynamic model based on Pitzer and Harvie's model was used to predict the composition of crystallized salts after water removal by forced evaporation and cooling from multicomponent solutions or brines. Initially, the salts’ solubilities in binary systems (NaCl–H 2 O, KCl–H 2 O and MgCl 2 –H 2 O) and ternary system (KCl–MgCl 2 –H 2 O) were calculated at 20 °C and compared with literature data. Next, the model was compared to our experimental data on the quinary system NaCl–KCl–MgCl 2 –CaCl 2 –H 2 O system at 20 °C. The Pitzer and Harvie's model represented well both the binary and ternary systems. Besides, for the quinary system the fit was good for brine densities up to 1350 kg/m 3 . The models were used to estimate the chemical composition of the solutions and salts produced by fractional crystallization and in association with material balance to respond to issues related to the production rates in a solar pond containing several salts dissolved, for instance, NaCl, KCl, MgCl 2 and CaCl 2 .

The present study investigated an evaluation efficiency of electrocoagulation (EC) for the pretreatment of a saline concentrated effluent from the reverse electrodialysis (RED-C) stage from an oil refinery, aiming at water reuse in the industrial process. In this approach, an electrocoagulation system with 1 L capacity was set up for batch treatment using aluminum electrodes. Initially, experiments with a semi-synthetic RED-C effluent were assessed for contaminants removal using fixed current density of 8.30 mA/cm2 and 1 cm distance between electrodes. The influence of initial pH (5 and 7), controlled temperature (20, 30 and 40°C) and operation time (60 and 120 min) on removal efficiency was investigated and solid residue were measured. The results showed that the optimum conditions were at pH 7 and 20-30°C with removal rates around 70%, 57%, 10% and 44% for Ca, Sr, Na and COD, respectively. Thereafter, experiments were conducted with a real RED-C using the best condition founded in preliminary tests, this time applying a current density of 5 and 10 mA/cm2 and 0.5 cm distance at room temperature (approximately 23°C). Regarding the tests with real RED-C, for both current densities the removals were greater due to decrease in distance between electrodes and larger temperature range that improved electrocoagulation. In general, the use of current density of 10 mA/cm2 and reduction of inter-electrode distance increased EC efficiency which exhibited removal rates of 88%, 77%, 26% and 24% for Ca, Sr, Na and COD, respectively. Although, it was observed a decrease in COD removal from real RED-C due to the addition of inorganic ions in the semisynthetic effluent that precipitated as salts, removing more organic as a coadjuvant compound. The solid slugde production for this same condition were 5.65 g/L.

Avaliou-se no presente trabalho uma rota alternativa para a lixiviação de minérios de ouro de baixo teor para se integrar a uma planta industrial no Uruguai que atualmente emprega o processo Carbon in Leaching (CIL). Diversos ensaios de lixiviação utilizando-se a técnica bottle roll test de 20 litros e colunas de 3 metros foram realizados visando-se estabelecer alguns parâmetros, critérios de operação e dimensionamento para avaliar um processo industrial de lixiviação para tratar cerca de 1.000.000 de toneladas de minério contendo cerca de 0,65 g de ouro por tonelada de minério (g/t). Foram concebidas pilhas de 4 metros de altura, minérios com uma granulometria 80% menor que 12,67 mm (P80 de 12,76mm), tempo de operação de 3 anos e atingindo-se uma produção anual de 455 quilogramas de ouro.doi: https://doi.org/10.18540/2446941602022016029

Este trabalho foi realizado visando-se obter o custo de investimento necessario (CAPEX) e o custo de operacao (OPEX) para uma planta industrial de lixiviacao de minerios de ouro de baixo teor para uma industria cujo processo inclui a lixiviacao e adsorcao do ouro pelo processo CIL (Carbon in Leaching) na regiao da Ilha Cristalina de Rivera no Uruguai (ICR). Os parâmetros de operacao do processo adotados foram baseados em ensaios segundo a tecnica “rolling bottles” em frascos de 20 litros e colunas de 3 metros. Foram definidos os criterios de operacao e dimensionamento para uma planta de lixiviacao em pilhas dinâmicas para 1.000.000 de toneladas de minerio de ouro de baixo teor (0,65 g/t) com granulometria proposta de 12,7 mm. Para a analise de viabilidade considerou-se a existencia das linhas de producao ja existentes de adsorcao, dessorcao e fundicao que podera contribuir com um incremento na producao anual de ouro de ate 24%. O projeto apresenta viabilidade economica com um Valor Presente Liquido (VPL) de 8.649.276 US$, uma Taxa Interna de Retorno (TIR) de 31,21% e payback descontado de 2,10 anos operando durante 3 anos.

The generation of liquid effluents with high organic and inorganic load in the petroleum industry requires proper treatment in order to prevent environmental pollution. Commonly, refractory organic compounds, which are not easily degraded by conventional methods, require an advanced treatment step. In addition, the inorganic content may negatively interfere with the treatment process due to scaling formation derived from the precipitation of low solubility compounds, primarily strontium and calcium-based salts. The present study aims at the removal of fouling metals such as calcium and strontium and refractory organic matter from the oil industry effluent by electrocoagulation associated with adsorption using coconut husk carbon considering the context of zero liquid discharge. Simultaneous electrocoagulation associated with adsorption presented an economy of the treatment time and capital cost in relation to the process carried out by individual steps of adsorption followed by electrocoagulation, because the efficiencies were similar. The treatment resulted in a residual of 25 mg(O2).L−1 (52 % removal) of organic matter measured as COD, 88 % of calcium removal (residual of 6.0 mg.L−1) and 72 % of strontium removal (residual of 0.4 mg.L–1), which improved the quality of the recovered water. In addition, it is noted that the adsorption process removed the organic compounds preferably while the metals were removed by electrocoagulation.

A biotita é um filossilicato ferromagnesiano que contém potássio. Ela é muito abundante e dispersa em todas as regiões do mundo. Formada secundariamente nos processos metamórficos constitui impureza em muitos processamentos minerais e descartada em bacias de estéreis ou de rejeito. É uma fonte alternativa de potássio para produção de fertilizante, porém, ainda sem exploração comercial em grande escala, para este propósito, por falta de tecnologia que torne o negócio viável economicamente. O objetivo deste trabalho foi investigar o efeito do processamento térmico, usando aditivos, na solubilização do potássio e impurezas em ácido mineral diluído, de rocha contendo biotita. Foi selecionada uma rocha da província mineral de Carajás–Pará – Brasil, com teor de 9,7% de K₂O e 70% de biotita. O processamento térmico foi executado em duas temperaturas, 800°C e 900°C, durante 6h, usando dois sistemas de misturas: (biotita+CaCO₃+MgCl2.6H2O) e (biotita+gesso+Na₂CO₃). A etapa de lixiviação ácida sulfúrica foi executada em pH mantido entre 2,0 e 3,0, temperatura de 85℃, durante 1h. As extrações, no sistema com cloreto de magnésio (800°C), chegaram a 63% do potássio e com solubilização máxima de 5% de Fe e Al. As extrações de potássio com gesso ficaram menores, 41%, mostrando tendência de melhor eficiência em temperaturas mais altas do que as escolhidas para este estudo, porém, com licor efluente da lixiviação isento de alumínio e 1,2% máximo de extração de ferro.

The use of anti-diabetic drugs has been increasing worldwide and the evolution of therapeutics has been enormous. Still, the currently available anti-diabetic drugs do not present the desired efficacy and are generally associated with serious adverse effects. Thus, entirely new interventions, addressing the underlying etiopathogenesis of type 2 diabetes mellitus, are required. Chalcones, secondary metabolites of terrestrial plants and precursors of the flavonoids biosynthesis, have been used for a long time in traditional medicine due to their wide-range of biological activities, from which the anti-diabetic activity stands out. : This review systematizes the information found in literature about the anti-diabetic properties of chalcones, in vitro and in vivo. Chalcones are able to exert these properties by acting in different therapeutic targets: Dipeptidyl Peptidase 4 (DPP-4); Glucose Transporter Type 4 (GLUT4), Sodium Glucose Cotransporter 2 (SGLT2), α-amylase, α-glucosidase, Aldose Reductase (ALR), Protein Tyrosine Phosphatase 1B (PTP1B), Peroxisome Proliferator-activated Receptor-gamma (PPARγ) and Adenosine Monophosphate (AMP)-activated Protein Kinase (AMPK). Chalcones are, undoubtedly, promising anti-diabetic agents, and some crucial structural features have already been established. From the Structure-Activity Relationships analysis, it can generally be stated that the presence of hydroxyl, prenyl and geranyl groups in their skeleton improves their activity for the evaluated anti-diabetic targets.

Radioactive wastewaters from nuclear source of electrical energy production need to be treated and disposed of properly. Sr, Ca, Mg and Ba are common elements in this effluent, which can cause incrustation in process equipments and being unsafe to human health (90Sr). Fixation of CO2 can be applied to remove the ions mentioned before and to provide a solution where CO2 is sequestered and the deleterious elements precipitated, becoming one of the possible steps to reuse the water into the process. Moreover, removal of several metals from distinct wastewater has been evaluated using bone char through adsorption. The chemical similarity between calcium and strontium makes the exchange of these two metals favorable in the hydroxyapatite structure contained in bone char. This paper evaluated the combined action of precipitation and adsorption process with injection of CO2 and bone char addition in simulated nuclear wastewater. Removal levels of 89.0% (Sr) and 83.3% (Ca) were obtained in the combined process. The presence of bone char as seed increased the precipitation kinetics, allowing a Sr removal of 85.2% in five minutes, higher than 75.3% obtained in absence of seeds. However, removal of 91.6% (Sr) and 89.8% (Ca) were obtained in absence of seeds at 24 h. Analysis of solids have evidenced that CO2 was consumed to precipitate the metals as carbonates, since the hydroxides are formed at higher pH’s.

Atmospheric processing of nickel lateritic ores with low costs has been encouraged. In this work the kinetic of atmospheric acid leaching of a northern-Brazilian ore with 1.63% Ni and large amount of fine particles (d50 ≈ 0.075 mm and 40% below 0.038 mm) is presented. Chemical analysis showed a trend of Ni and Fe concentration in finer fraction (−0.075 mm) and Si and Mg in the coarsest one (−0.500 + 0.150 mm) associated to distinct mineral phases. Nickel is widespread in the mineral matrix. Distinct behaviors were observed as a function of particle size associated to the distribution of silicates and iron oxides in the ore. The kinetic modeling indicated that leaching is controlled by porous layer diffusion at 65 °C, but at 95 °C exhibits a mixed control by porous layer diffusion in initial minutes (60 min) and by chemical reaction or diffusion through the pore layer in final minutes (60–240 min) depends on metal evaluated.

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N2-BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q = 6.2 ± 0.5 mg/g) and Al-doped (q = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C 0 → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F−/L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F−]feed ∼ 9 mg/L; flow rate = 1 mL/min; m sorbent = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

The homogeneous and seed-assisted precipitation of dicalcium phosphate dihydrate (DCPD or brushite) and hydroxyapatite (HAP) under controlled supersaturation regimes in chloride media at room temperature (22 °C) is investigated. Prior to their reactive crystallization the metastable zones of precipitation for the two calcium orthophosphates were determined. The effects of supersaturation, reaction time, and seeding on the stoichiometry and crystallinity of these compounds were studied. Acidified solutions (pH ≈ 2.0) of NaH 2 PO 4 (2-90 mmol/L) and CaCl 2 (2-150 mmol/L) were mixed in order to get Ca to P molar ratios in initial solution of 1.0 or 1.67 (the stoichiometric ratios for dicalcium phosphate dihydrate and hydroxyapatite).The supersaturation in solution was built up by the slow addition of 100 mmol/L NaOH solution. In seed-assisted precipitation tests (Ca/P = 1) the metastable calcium phosphate solution (37.5 mmol/L) was neutralized until the precipitation pH of 5 was reached and 10 g/L of seed was added. The homogeneous precipitation of DCPD at pH 5.4 was fast and equilibrium was reached in 30 min. In the presence of seed, the precipitation rate was slower due to reduced supersaturation. Even so, in both cases well crystalline plate-like crystals matching the stoichiometry of brushite were produced. Calcium-deficient hydroxyapatite with nanocrystalline structure (nanocrystallite size ∼20 nm) was produced at pH 7.6 under controlled supersaturation. The homogeneously produced material consisted of irregularly shaped agglomerates of the order of 5―15 μm while the product obtained by seed-assisted precipitation was in the form of rather coarse (ca. 20―30 μm) and dense spheroids. The highest Ca:P ratio material (Ca:P = 1.58) was obtained with seed-assisted precipitation at a slow addition rate.

A prática do coprocessamento de resíduos na indústria de cimento tem se expandido devido à necessidade crescente de uma destinação ambiental e socialmente mais adequada de resíduos perigosos provenientes de diversos processos industriais. O objetivo deste trabalho foi realizar uma revisão sobre o coprocessamento de resíduos em fornos de clínquer, no Brasil e no mundo, visando contribuir para a otimização dos processos, identificando os aspectos já estudados e os que ainda demandam pesquisas. Foram abordados aspectos socioambientais e tecnológicos do coprocessamento, bem como a análise do ciclo de vida (ACV) na produção de cimento, e a produção técnico-científica sobre o coprocessamento.

A prática do coprocessamento de resíduos na indústria de cimento tem se expandido devido à necessidade crescente de uma destinação ambiental e socialmente mais adequada de resíduos perigosos provenientes de diversos processos industriais. O objetivo deste trabalho foi realizar uma revisão sobre o coprocessamento de resíduos em fornos de clínquer, no Brasil e no mundo, visando contribuir para a otimização dos processos, identificando os aspectos já estudados e os que ainda demandam pesquisas. Foram abordados aspectos socioambientais e tecnológicos do coprocessamento, bem como a análise do ciclo de vida (ACV) na produção de cimento, e a produção técnico-científica sobre o coprocessamento.The practice of co-processing of residues has increased due to the requirement of environmental and social friendly disposal of dangerous wastes from several industrial processes. The aim of this work was to perform a revision of co-processing of residues in Brazil and in the world, aiming at process optimization and also to identify the aspects already studied as well as those which still request research efforts. Social, environmental, and technological aspects of co-processing were discussed in the present work as well as the life cycle analysis (LCA) in the cement production and the technical and scientific literature about co-processing.

A new stabilization process for scorodite (FeAsO(4).2H(2)O) solids based on the concept of encapsulation by controlled deposition of mineral coatings immune to pH or redox potential variations is described. The stability of the encapsulated scorodite with aluminum phosphates under simulated anoxic and oxic environments is demonstrated. Encapsulation experiments were carried out at 95 degrees C using 50 g/L scorodite in acidic sulphate solution containing 0.16 mol/L of P(V) with Al(III) to P(V) molar ratio of 1 and precipitation pH of 1.7. The encapsulated particles were characterised by XRD, SEM, TOF-SIMS and TOF-LIMS. The coating was crystalline AlPO(4).1.5H(2)O ranging in thickness from 2.5 to 3.5 microm. Encapsulation of scorodite particles with hydrated aluminum phosphate appears to be effective in controlling/suppressing the release of arsenic under both oxic and anoxic conditions by more than one order of magnitude.

Enriched arsenic precipitates were obtained from dilute industrial As(III) solutions (1.1–0.1 g As/L) at 95 °C in batch and continuous reactor operations. A complete and fast oxidation of As(III) was obtained at room temperature with 20% excess of hydrogen peroxide. Arsenic removal varied from 80.5 to 94.6% and increased with the total surface area (SSA) of the seed. SSA higher than 270 m 2 /g was required to promote an arsenic removal of approximately 85%. Recycling of solids was necessary to achieve high yields of arsenic removal in continuous operation. Approximately 75 to 85% As was removed in 1 h of residence time in the MSMPRR (Mixed Suspension Mixed Product Removal with Solids Recycle) reactor; the rate of crystal growth was calculated as 10 − 12 m/s. Arsenic removal was not favored by the excess of iron in the solution. TCLP (Toxicity Characterization Leaching Procedure) testing indicated that ageing plays an important role in the leachability of scorodite, which decreased from 13.6 mg As/L to 0.1 mg As/L after 8 h in a batch reactor. The decrease in As leachability was related to the decrease in the SSA (14 m 2 /g to 0.9 m 2 /g after 62 h in the MSMPRR) as a combination of crystal growth (1.6 μm to 5.3 μm) and densification. Scorodite was the only arsenic phase identified by X-ray diffraction and micro-Raman analyses of the precipitates.

Os métodos de precipitação química, cristalização e extração líquido-líquido foram aplicados visando propor alternativas para o tratamento de efluentes líquidos gerados pela indústria de galvanoplastia. Efluentes de diversas empresas do setor, localizadas no estado de Minas Gerais (Brasil), foram coletados e caracterizados. O efluente estudado, proveniente de empresa de galvanização de zinco a quente, continha cerca de 90 g/L de ferro total, 35 g/L de zinco e menores quantidades de Al, Ni e Cu, em meio ácido clorídrico (pH = 0,6). A separação seletiva entre ferro e zinco não se mostrou eficiente por precipitação, sendo a técnica adequada somente no tratamento do efluente, ao contrário da cristalização e extração líquido-líquido utilizando-se TBP como agente extratante. A integração destas técnicas ainda requer estudos mais detalhados visando à otimização de custos e das condições operacionais.Separation methods such as chemical precipitation, crystallization and liquid-liquid extraction have been investigated aiming to treat effluents generated by the galvanic industry. Effluent samples generated by several companies located in the state of Minas Gerais (Brazil) were collected and chemically characterized. For this work, a typical zinc hot-dip galvanizing effluent containing about 90 g/L of total iron, 35 g/L of zinc and minor amounts of Al, Ni, Cu, in HCl medium (pH = 0.6) was treated. A selective separation between metals zinc and iron was not achieved by chemical precipitation, which was found adequate to threat water only. On contrary, zinc and iron was separated very efficiently by crystallization and liquid-liquid extraction using TBP as extractant agent. The integration of these methods to recover zinc and iron from effluent still requires more detailed studies.

The objective of this work was to propose an alternative use for coffee husks (CH), a coffee processing residue, as untreated sorbents for the removal of methylene blue (MB) from aqueous solutions. The effects of solution temperature, pH, biosorbent dosage and contact time on MB removal were investigated. The experimental adsorption equilibrium data were fitted to both Langmuir and Freundlich adsorption models. The biosorption kinetics was determined by fitting first and second-order kinetic models to the experimental data, with the second-order model providing the best description of MB adsorption onto coffee husks. pH variations did not present a significant effect on MB removal. Evaluation of thermodynamics parameters indicated that the adsorption is spontaneous and endothermic. The experimental data obtained in the present study demonstrated coffee husks to be suitable candidates for use as biosorbents in the removal of cationic dyes.

The liquid–liquid extraction of zinc using D2EHPA as extractant has been investigated in this paper in order to recover zinc sulphate from an industrial effluent produced by Votorantim Co. (Brazil) which contains several metallic species such as cadmium, cobalt, iron, lead, calcium, magnesium, manganese and nickel. The study was carried out in two main steps: (1) extraction and stripping laboratory scale tests in order to assess adequate operational conditions for the favourable recovery of zinc from the effluent and (2) continuous pilot scale tests using a mixer-settler battery aiming to reproduce the bench results. In the laboratory scale experiments, operating variables such as the pH of the aqueous effluent (0.5–5.0), concentration of D2EHPA (5–50%,w/w) and aqueous/organic volumetric phase ratio (1/5–5/1) were investigated for the zinc extraction process; for the zinc stripping process, the organic/aqueous volumetric phase ratio (1/1–10/1) was studied by contacting a metal loaded organic phase with an industrial acid solution produced by the company in the electrolysis of zinc. The continuous mixer-settler tests have shown that zinc can be selectively and quantitatively removed from the effluent (around 98%) using 3 extraction stages (pH 2.5, [D2EHPA] = 20% (w/w) and A/O = 1), and other 3 stripping stages (O/A = 4). A final solution containing 125.7 g/L of zinc was obtained that could be sent directly to electrowinning.

The kinetics of magnesia hydration to produce magnesium hydroxide is crucial for process design and control, and for the production of an Mg(OH)2 powder with desirable particle morphology. In this study, highly pure magnesia has been hydrated in a batch reactor. The effects of the following variables were evaluated experimentally: temperature (308–363 K), reaction time (0.5–5 h), initial slurry density (1–25%wt) and particle size in the ranges −212 + 75 µm and −45 + 38 µm. Experimental data indicate increasing magnesia hydration rates with increasing temperature, as expected. In addition, it has been observed that the hydration of magnesia increases significantly up to about 4–5%wt initial slurry density, stabilising afterwards. On the other hand, the reaction was almost unaffected when magnesia with different particle sizes were hydrated because of similar specific surface areas involved. A reaction mechanism to explain the oxide dissolution and the hydroxide precipitation has been proposed, assuming no significant change in the initial solids size and dissolution rate as the controlling step. The calculated activation energy value of 62.3 kJ mol−1 corroborates the mechanism proposed in this study and compares well with values previously reported in the literature. Copyright © 2004 Society of Chemical Industry

Advances in technologies to enable water reuse in industry have been the objective of many research efforts, mainly due to the need to reduce the use of natural resources and due to factors related to their availability. This paper evaluates the crystallization of salts from petrochemical saline waste to achieve zero water discharge by the recovery of water and dissolved salts as a solid mixture. In line with process symbiosis, the recovered water should be suitable for use as cooling water in heat exchangers. Vacuum evaporative crystallization, at the batch scale, was used to remove the salts present in the concentrated stream from reverse electrodialysis of pretreated wastewater by a biological process. The partition of organic compounds in the feed solution between the condensate and the mother liquor was obtained from measurements of the total organic carbon and total nitrogen in the solutions. The solid phases formed experimentally are compared with those predicted by chemical modelling by PHREEQC. The recovered water presented almost 50 times less total dissolved solids than the feed stream (from 2100 to 44 mg/L). Calcium sulphate hydrate, calcium sulphate and sodium chloride were the majority crystalline phases formed, in accordance with the modelling by PHREEQC.

The present work investigates the use of magnesium hydroxide, produced by magnesia hydration, as a fire retardant in polymers. The hydration was carried out in an autoclave, at temperature of 130°C for 1 hour, and the product was further submitted to cominution in a jet mill. The solids were characterized with regard to their chemical composition, particle size distribution, surface area and morphology. The performance evaluation of the hydroxide as a flame retardant for a copolymer of nylon 6-6,6 was carried out according to the UL94 specifications for vertical burning tests. V-0 flammability rating at 1.6 mm (60% magnesium hydroxide-filled nylon composite) and at 3.2 mm (40% magnesium hydroxide filled nylon composite) were achieved. Mechanical properties were maintained at the desired values. These results indicate that the hydroxide obtained from magnesia hydration can be successfully employed as a fire retardant for nylon 6-6,6.

The kinetics of the hydration of magnesia to produce magnesium hydroxide is described by a kinetic model with no diffusive contribution, including an additional resistance to the reactive flux due to the transient variation of the porosity of the material during reaction. The proposed model has been applied to data from the literature and obtained by hydration of MgO samples with distinct physical characteristics. The model describes well the mechanism of hydration of powder and single crystal MgO in liquid and vapour water with temperatures varying from 35°C to 200°C. La cinetique d'hydratation de la magnesie pour produire de l'hydroxyde de magnesium est decrite par un modele cinetique sans contribution diffusive, incluant une resistance additionnelle au flux reactif en raison de la variation transitoire de la porosite du materiau lors de la reaction. Le modele propose a ete applique a des donnees venant de la literature scientifique et a ete obtenu par hydratation d'echantillons de MgO ayant des caracteristiques physiques distinctes. Ce modele decrit bien le mecanisme d'hydratation du MgO en poudre et monocristal dans du liquide et de la vapeur d'eau pour des temperatures variant entre 35°C et 200°C.

The aim of this work was to analyze the effect of magnesite calcination conditions, i.e. kiln temperature and residence time, on magnesia response to activity tests and, further, the relationship of this response with MgO hydration behavior under different reaction conditions. The calcination of magnesite was carried out at various temperatures and residence times, in lab-scale Herreshoff and electrical kilns. The solids were characterized with respect to their chemical and physical properties, and then hydrated under different temperature and time. Magnesia activity was compared to the sample surface areas and the corresponding hydration levels. It is demonstrated that the activity test should be used with caution once its suitability to predict hydration behavior of magnesia depends on the sample's characteristics and the conditions in which hydration will take place.

Os métodos de precipitação química, cristalização e extração líquido-líquido foram aplicados visando propor alternativas para o tratamento de efluentes líquidos gerados pela indústria de galvanoplastia. Efluentes de diversas empresas do setor, localizadas no estado de Minas Gerais (Brasil), foram coletados e caracterizados. O efluente estudado, proveniente de empresa de galvanização de zinco a quente, continha cerca de 90 g/L de ferro total, 35 g/L de zinco e menores quantidades de Al, Ni e Cu, em meio ácido clorídrico (pH = 0,6). A separação seletiva entre ferro e zinco não se mostrou eficiente por precipitação, sendo a técnica adequada somente no tratamento do efluente, ao contrário da cristalização e extração líquido-líquido utilizando-se TBP como agente extratante. A integração destas técnicas ainda requer estudos mais detalhados visando à otimização de custos e das condições operacionais. Separation methods such as chemical precipitation, crystallization and liquid-liquid extraction have been investigated aiming to treat effluents generated by the galvanic industry. Effluent samples generated by several companies located in the state of Minas Gerais (Brazil) were collected and chemically characterized. For this work, a typical zinc hot-dip galvanizing effluent containing about 90 g/L of total iron, 35 g/L of zinc and minor amounts of Al, Ni, Cu, in HCl medium (pH = 0.6) was treated. A selective separation between metals zinc and iron was not achieved by chemical precipitation, which was found adequate to threat water only. On contrary, zinc and iron was separated very efficiently by crystallization and liquid-liquid extraction using TBP as extractant agent. The integration of these methods to recover zinc and iron from effluent still requires more detailed studies.

The selective removal of zinc(II) over iron(II) by liquid-liquid extraction from spent hydrochloric acid pickling effluents produced by the zinc hot-dip galvanizing industry was studied at room temperature. Two distinct effluents were investigated: effluent 1 containing 70.2g/L of Zn, 92.2g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9g/L of Fe and 2M HCl. The following extractants were compared: TBP (tri-n-butyl phosphate), Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid], Cyanex 301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid] and Cyanex 302 [bis(2,4,4-trimethylpentyl) monothiophosphinic acid]. The best separation results were obtained for extractants TBP and Cyanex 301. Around 92.5% of zinc and 11.2% of iron were extracted from effluent 1 in one single contact using 100% (v/v) of TBP. With Cyanex 301, around 80-95% of zinc and less than 10% of iron were extracted from effluent 2 at pH 0.3-1.0. For Cyanex 272, the highest extraction yield for zinc (70% of zinc with 20% of iron extraction) was found at pH 2.4. Cyanex 302 presented low metal extraction levels (below 10%) and slow phase disengagement characteristics. Reactions for the extraction of zinc with TBP and Cyanex 301 from hydrochloric acid solution were proposed.

This paper proposes a simple methodology for simulation of equilibrium FCC catalyst (e-cat) performance, employing techniques such as metal impregnation followed by hydrothermal deactivation and laboratory catalyst evaluation. The laboratory evaluation of samples deactivated under different conditions including the e-cat were used in an optimization algorithm, to determine the mixture that best mi overall e-cat performance in terms of activity and main product yields. The proposed methodology may be used in order to establish a specific deactivation protocol for any particular FCC unit.