An inorganic sludge from construction and demolition wastes (ICDW) was grafted with APTES to obtain an inorganic-organic modified adsorbent ICDW-APTES. This adsorbent was successfully employed for ...ciprofloxacin (CFX) adsorption and treatment of synthetic hospital effluent. The chemical composition of ICDW presented large quantities of SiO2 and Al2O3, which supports its application for being functionalized by APTES that occurred through a chemical reaction between the surface oxygen groups of oxides with the silanol groups of the APTES. The characterization data suggested that APTES was successfully grafted on the ICDW structure. The kinetic studies showed that the general-order provided the best fitness for CFX adsorption on ICDW-APTES. Liu isotherm model presented the best fitness for the equilibrium studies, and it provided a Qmax of 138.0 mg g−1 at 40.0 °C. Electrostatic interaction was the primary mechanism involved in the adsorption process. The ICDW-APTES also exhibited a good percentage of removal of the two synthetic effluents (71.0 % and 69.0 %).
Vanadium and nickel in emissions from fossil-fuel combustion and in the fly ash can be an environmental concern. The fly ash from the combustion of a 70% coal/30% petroleum coke blend in a 500 MW ...pulverized-fuel utility boiler was studied by a variety of X-ray, optical microscopy, and electron beam methods. The fly ash V and Ni are present in heterogeneous silicates, glass, sulfates, oxides and oxyhydroxides, and crystalline and/or amorphous mixed clay minerals, and also in Ni, detrital ferromagnesian silicates. Vanadium- and Ni-bearing spinels are incorporated into magnetite structures. Multiwalled nanotubes encapsulate V and Ni, and C60, C70, and C80 fullerenes and their derivatives are present.
Aluminum recycling generates large amounts of hazardous wastes, known as salt slags, consisting mainly of oxides, metallic aluminum, and salt fluxes. Water leaching is a common technique used for ...salt removal, being a decisive operation due to water usage and the need to achieve sufficient salt recovery. In this study, water leaching tests under varied operational conditions (water type, slag particle size, solid content, and leaching time) were carried out in salt slag samples obtained from a Brazilian aluminum scrap melting company. Leaching efficiency was assessed by the % chlorine leached. The optimal leaching condition, defined as the one that resulted in the highest chloride removal from the slag together with appropriate operational conditions (larger viable slag size, lower leaching time, etc.), was identified for a slag size below 2.8 mm, 30 wt% of solids in pulp, and a leaching time of 90 min. The results showed that it was possible to recover more than 92% of the salts initially contained in the raw slag, resulting in a leached material with less than 2.5% salts. The recovered salt characteristics showed potential for recycling and could be re-mixed to the salt flux used for aluminum melting. The possibility of achieving higher efficiencies and lower water consumption during leaching was also discussed, as was a preliminary flowsheet for salt slag treatment.
Artisanal and small-scale processes of dyeing of agates are usually non standardized and often ineffective. In the Brazilian scenario, local arrangements need actions to improve the current processes ...and to minimize energy consumption and production of wastes. In this sense, the aim of this study was to investigate new standard dyeing procedures capable of producing a satisfactory color alteration using minimal quantities of inorganic dyes and heat. A so-called cold dyeing route was outlined and tested for the artificial colors black, red, blue and green. In all cases, experimental results showed a significant, and in some cases dramatic, improvement in the final color of agates dyed according to the proposed cold dyeing system in comparison to the conventional warm process. Most important, these improvements were achieved with an average reduction of heat energy and reactant consumption of 94.6% and 56.6%, respectively. Potential benefits obtained from applying the cold dyeing route include the reduction of operating costs and decrease in wastewater burden due to the use of dye solutions of low concentrations under optimized conditions.
•Local artisanal and small-scale practices of dyeing of agates are not standardized.•New dyeing processes using minimal amounts of reactant and energy were proposed.•A better color alteration was achieved with pieces dyed according to the new route.•Optimization of cold dyeing processes led to substantial energy savings.
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•Sustainable and efficient powdered activated carbon (SP-AC) from soybean pods.•Lanthanum and cerium recovery from real leachate.•The maximum capacities for Ce(III) and La(III) were ...107.7 and 127.2 mg g−1.•The adsorption mechanisms proposed by statistical physics approach.•SP-AC recovered 90% of Ce and 96% of La from real phosphogypsum leachate.
In this study, we aimed to produce a sustainable and efficient powdered activated carbon (SP-AC) and evaluate its adsorptive abilities to uptake and recover rare earth elements (REEs) from synthetic solutions containing lanthanum (La(III)) and cerium (Ce(III)), and real leachate, from phosphogypsum, containing several REEs. The adsorbent material was subjected to several characterization techniques to understand its physicochemical and adsorptive properties. The characterization results indicated that the activated carbon prepared in this work possesses a specific surface area, pore volume, and average pore diameter of 614 m2g−1, 0.121 cm3g−1, and 3.65 nm, respectively. Interestingly, the adsorbent material exhibited a highly negatively charged surface which was extremely beneficial for La(III) and Ce(III), which are positively charged and therefore were easily attracted to each other. The kinetic data were well fitted by pseudo-second-order, while the Liu model agreeably fitted equilibrium data. The maximum adsorption capacities for Ce(III) and La(III) were 107.7 and 127.2 mg g−1 at 298 K, respectively. The thermodynamic data indicated that the adsorption systems between SP-AC and both REEs were favorable, spontaneous, and exothermic. The adsorption mechanisms between SP-AC and the two REEs were proposed based on the experimental results, adsorbent characteristics, and statistical physics approach. Pore filling and ion exchange were the main mechanisms, although surface complexation was also involved. Finally, the SP-AC was employed to recover many REEs from real phosphogypsum leachate, demonstrating that SP-AC can selectively recover REEs in the real process.
Chitin powder and chitin-aerogel were prepared from shrimp wastes and used to uptake Y3+ from aqueous solutions and concentrate this rare earth element from phosphogypsum (PG). Chitin aerogel ...displays a specific surface area of 945 m2/g, while chitin powder is 3.6 m2/g, which largely influences its adsorption ability. Regarding the adsorption in synthetic solutions, the effect of pH on Y3+ removal is strong for chitin powder adsorbent. In contrast, no big pH influence was detected for chitin aerogel. Electrostatic interactions and chelation can highlight the proposed mechanism of Y3+ on chitin adsorbents for the powder and aerogel. Furthermore, in addition to these interactions, pore filling/pore diffusion is the main mechanism of Y3+ removal in the chitin aerogel. Chitin aerogel is efficient in concentrating 8 times the Y3+ from PG, a very complex matrix. The complex chitin aerogel-Y3+ can be a secondary source of rare earth elements for other applications.
Scheme for the yttrium (Y3+) adsorption using the chitin-based adsorbents. Display omitted
A ágata do sul do Brasil, apresenta colorações pouco interessantes ou salientes, sendo predominante os tons acinzentados. Tais qualidades, foram fatores determinantes para o início do processo de ...tingimento de ágata do Rio Grande do Sul, no século XVIII. Atualmente, o segmento mineral, apresenta carências relacionadas a tecnologias e processos de produção, além de infraestruturas inadequadas, resultando em prejuízo para as comunidades produtoras. Nesse cenário, a pesquisa se estrutura para avaliar técnicas operacionais viáveis para o setor, objetivando a melhoria do valor agregado às gemas beneficiadas e qualidade da cor. Para o desenvolvimento do tratamento em preto, o sistema foi replicado, padronizado e otimizado no Laboratório LAPROM da UFGRS e Centro Tecnológico de Pedras, Gemas e Joias do Rio Grande do Sul. A amostragem foi classificada em quatro padrões e analisada em espectrofotômetro. Ao término, se tem a comparação dos resultados do tingimento otimizado e o convencional, com as curvas de distribuição espectral medidas antes e após o tratamento termoquímico da ágata. Com o sistema otimizado, foi possível reduzir custos operacionais, tempo de energia envolvida no sistema, manter da qualidade da cor e relacionar com a proporção de reagentes usados.
O carvão mineral brasileiro contém altos teores de impurezas (pirita e minerais de rochas sedimentares), sendo necessário seu beneficiamento. Os rejeitos do beneficiamento demandam uma grande área ...física para a sua disposição, modificam a topografia e geram a drenagem ácida de minas (DAM). O objetivo desse trabalho foi caracterizar um típico depósito de rejeitos na região carbonífera de Santa Catarina, buscando a separação de três frações para uso futuro: (a) uma fração para a geração de energia; (b) uma fração enriquecida em silicatos; e (c) uma fração com alto teor de enxofre. A metodologia do trabalho consistiu na amostragem e caracterização do material. A caracterização incluiu análise granulométrica, estudos densimétricos, medidas do teor de cinzas e enxofre, análise mineralógica por DRX, estudos petrográficos em lupa e medidas de contabilização de ácidos e bases. Os resultados granulométricos indicaram que 68% do material é composto por partículas grossas, 15%, por partículas finas e 17%, pelo lodo das bacias de sedimentação. Com o beneficiamento gravimétrico dos resíduos é possível uma recuperação teórica do material de 33,7% para geração de energia e 10,3% para produção de um concentrado rico em pirita. O material restante, com menor quantidade de enxofre e rico em silicatos, tem seu potencial de geração de acidez reduzido em 60% e apresenta possibilidade de uso na construção civil.
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