PRODUÇÃO E AVALIAÇÃO DE CARVÕES ATIVADOS OBTIDOS EM DIFERENTES FASES DE ESTABILIZAÇÃO DO LODO DE ESGOTO

O aumento exponencial na produção de lodo de esgoto, decorrente da melhoria dossistemas de tratamento sanitário em grandes centro urbanos, pode representar um problemaambiental se este não for disposto adequadamente. Converter lodo de esgoto em adsorventesatravés da pirólise tem sido proposto desde 1971 como alternativa a destinação final desteresíduo. Como alternativa para disposição do excesso de lodo que é retirado do reator UASBna Estação de Tratamento de Esgoto Subaé, Feira de Santana, Bahia, a proposta deste trabalhofoi obter carvão ativado em diferentes fases de estabilização do lodo de esgoto e avaliar suacapacidade de adsorção na remoção do azul de metileno em solução aquosa. As propriedadesdo lodo como sólidos totais e voláteis totais, carbono orgânico, nitrogênio, foramdeterminadas seguindo recomendações do Standard Methods APHA. As amostras de lodoforam pirolisadas a 450°C sob atmosfera inerte e o carvão ativado produzido foi caracterizadopor CHN, adsorção de nitrogênio e ensaios de adsorção. Pelas análises físico-químicas, o lodode esgoto apresentou baixos teores de carbono e nutrientes, independentemente do tempo deretenção no leito de secagem, quando comparados a típicos Iodos de sistemas anaeróbios. Osespectros de infravermelho confirmam a presença de grande quantidade de silicatosdecorrente da baixa eficiência da ETE-Subaé. Os ensaios de adsorção, usando o azul demetileno como adsorvato, mostraram que estes carvões são adsorventes potenciais pararemoção de corantes em efluentes líquidos. As isotermas de adsorção foram estudadas e osresultados foram ajustados pelos modelos de Langmuir e Freundlich. O modelo de Langmuirdescreveu melhor o processo de adsorção. Os resultados da adsorção, grau de enriquecimentode carbono e a razão molar N/C, indicaram que a melhor amostra para preparar carvão ativadoda ETE-Subaé é o lodo LES08, àquela que permaneceu mais tempo no leito de secagem.</div

Synthesis of sustainable mesoporous sulfur-doped biobased carbon with superior performance sodium diclofenac removal: Kinetic, equilibrium, thermodynamic and mechanism

Over the last years, the strategy of employing inevitable organic waste and residue streams to produce valuable and greener materials for a wide range of applications has been proven an efficient and suitable approach. In this research, sulfur-doped porous biochar was produced through a single-step pyrolysis of birch waste tree in the presence of zinc chloride as chemical activator. The sulfur doping process led to a remarkable impact on the biochar structure. Moreover, it was shown that sulfur doping also had an important impact on sodium diclofenac (S-DCF) removal from aqueous solutions due to the introduction of S-functionalities on biochar surface. The adsorption experiments suggested that General and Liu models offered the best fit for the kinetic and equilibrium studies, respectively. The results showed that the kinetic was faster for the S-doped biochar while the maximum adsorption capacity values at 318 K were 564 mg g−1 (non-doped) and 693 mg g−1 (S-doped); highlighting the better affinity of S-doped biochar for the S-DCF molecule compared to non-doped biochar. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) suggested that the S-DCF removal on both adsorbents was spontaneous, favourable, and endothermic

Enhanced biobased carbon materials made from softwood bark via a steam explosion preprocessing step for reactive orange 16 dye adsorption

The growing textile industry produces large volumes of hazardous wastewater containing dyes, which stresses the need for cheap, efficient adsorbing technologies. This study investigates a novel preprocessing method for producing activated carbons from abundantly available softwood bark. The preprocessing involved a continuous steam explosion preconditioning step, chemical activation with ZnCl2, pyrolysis at 600 and 800 °C, and washing. The activated carbons were subsequently characterized by SEM, XPS, Raman and FTIR prior to evaluation for their effectiveness in adsorbing reactive orange 16 and two synthetic dyehouse effluents. Results showed that the steam-exploded carbon, pyrolyzed at 600 °C, obtained the highest BET specific surface area (1308 m2/g), the best Langmuir maximum adsorption of reactive orange 16 (218 mg g−1) and synthetic dyehouse effluents (>70 % removal) of the tested carbons. Finally, steam explosion preconditioning could open up new and potentially more sustainable process routes for producing functionalized active carbons

PRODUÇÃO E AVALIAÇÃO DE CARVÕES ATIVADOS OBTIDOS EM DIFERENTES FASES DE ESTABILIZAÇÃO DO LODO DE ESGOTO

O aumento exponencial na produção de lodo de esgoto, decorrente da melhoria dossistemas de tratamento sanitário em grandes centro urbanos, pode representar um problemaambiental se este não for disposto adequadamente. Converter lodo de esgoto em adsorventesatravés da pirólise tem sido proposto desde 1971 como alternativa a destinação final desteresíduo. Como alternativa para disposição do excesso de lodo que é retirado do reator UASBna Estação de Tratamento de Esgoto Subaé, Feira de Santana, Bahia, a proposta deste trabalhofoi obter carvão ativado em diferentes fases de estabilização do lodo de esgoto e avaliar suacapacidade de adsorção na remoção do azul de metileno em solução aquosa. As propriedadesdo lodo como sólidos totais e voláteis totais, carbono orgânico, nitrogênio, foramdeterminadas seguindo recomendações do Standard Methods APHA. As amostras de lodoforam pirolisadas a 450°C sob atmosfera inerte e o carvão ativado produzido foi caracterizadopor CHN, adsorção de nitrogênio e ensaios de adsorção. Pelas análises físico-químicas, o lodode esgoto apresentou baixos teores de carbono e nutrientes, independentemente do tempo deretenção no leito de secagem, quando comparados a típicos Iodos de sistemas anaeróbios. Osespectros de infravermelho confirmam a presença de grande quantidade de silicatosdecorrente da baixa eficiência da ETE-Subaé. Os ensaios de adsorção, usando o azul demetileno como adsorvato, mostraram que estes carvões são adsorventes potenciais pararemoção de corantes em efluentes líquidos. As isotermas de adsorção foram estudadas e osresultados foram ajustados pelos modelos de Langmuir e Freundlich. O modelo de Langmuirdescreveu melhor o processo de adsorção. Os resultados da adsorção, grau de enriquecimentode carbono e a razão molar N/C, indicaram que a melhor amostra para preparar carvão ativadoda ETE-Subaé é o lodo LES08, àquela que permaneceu mais tempo no leito de secagem

Application of design of experiments (DoE) for optimised production of micro- and mesoporous Norway spruce bark activated carbons

In this work, Norway spruce (Picea abies (Karst) L.) bark was employed as a precursor to prepare activated carbon using zinc chloride (ZnCl2) as a chemical activator. The purpose of this study was to determine optimal activated carbon (AC) preparation variables by the response surface methodology using a Box-Behnken design (BBD) to obtain AC with high specific surface area (S-BET), mesopore surface area (S-MESO), and micropore surface area (S-MICR). Variables and levels used in the design were pyrolysis temperature (700, 800, and 900 degrees C), holding time (1, 2, and 3 h), and bark/ZnCl2 impregnation ratio (1, 1.5, and 2). The optimal conditions for achieving the highest S-BET were as follows: a pyrolysis temperature of 700 degrees C, a holding time of 1 h, and a spruce bark/ZnCl2 ratio of 1.5, which yielded an S-BET value of 1374 m(2) g(-1). For maximised mesopore area, the optimal condition was at a pyrolysis temperature of 700 degrees C, a holding time of 2 h, and a bark/ZnCl2 ratio of 2, which yielded a S-MESO area of 1311 m(2) g(-1), where mesopores (S-MESO%) comprised 97.4% of total S-BET. Correspondingly, for micropore formation, the highest micropore area was found at a pyrolysis temperature of 800 degrees C, a holding time of 3 h, and a bark/ZnCl2 ratio of 2, corresponding to 1117 m(2) g(-1), with 94.3% of the total S-BET consisting of micropores (S-MICRO%). The bark/ZnCl2 ratio and pyrolysis temperature had the strongest impact on the S-BET, while the interaction between temperature and bark/ZnCl2 ratio was the most significant factor for S-MESO. For the S-MICRO, holding time was the most important factor. In general, the spruce bark AC showed predominantly mesoporous structures. All activated carbons had high carbon and low ash contents. Chemical characterisation indicated that the ACs presented disordered carbon structures with oxygen functional groups on the ACs' surfaces. Well-developed porosity and a large surface area combined with favourable chemical composition render the activated carbons from Norway spruce bark with interesting physicochemical properties. The ACs were successfully tested to adsorb sodium diclofenac from aqueous solutions showing to be attractive products to use as adsorbents to tackle polluted waters

Adsorption and recovery of phosphate from aqueous solution by the construction and demolition wastes sludge and its potential use as phosphate-based fertiliser

This study aimed to investigate phosphate removal from aqueous effluents by an inorganic sludge from the inert part of construction and demolition wastes (CSW) as adsorbent. It is also discussed the application of the loaded P adsorbent as potential fertiliser. The CSW was also thermally treated at 800¿°C for 2¿h (CSW-T), and its influence in the P removal was also investigated. The characterisation techniques highlighted low porosity on CSW and CSW-T adsorbents and that they are mainly formed by oxides which could enhance the P uptake and recovery. In pH experiments, P adsorption increased as initial pH increased, at pH higher than 7.8 the P removal sharply increased due to the formation of calcium phosphate precipitate. The mechanism of the P adsorption onto CSW indicated that the process was mainly controlled by chemical bonding or chemisorption. The results showed that CSW-T was more effective for P removal in comparison to CSW based on the Liu isotherm, the maximum sorption capacity attained was 24.04 (CSW) and 57.64¿mg¿g-1 (CSW-T). Based on the Avrami’s kinetic models, the time for attaining 95% of saturation was 212.6 (CSW), and 136.6¿min (CSW-T). CSW and CSW-T showed the highest phosphate-removal performance among many adsorbents found in the literature; therefore, this kind of waste can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the P loaded adsorbents could be used as potential fertilisers which could be an interesting and efficient way of reuse for this waste.Peer ReviewedPostprint (published version

Functionalization of corn stover with 3-aminopropyltrietoxysilane to uptake Reactive Red 141 from aqueous solutions

An alternative and low-cost adsorbent (CS–APTES) was developed by the functionalization corn stover (CS) with 3-aminopropyltrietoxysilane (APTES) using a simple method. Several analytical techniques were used to prove the functionalization and then, CS–APTES was employed to adsorb Reactive Red 141 (RR141) dye from aqueous solutions. The functionalization with APTES caused an increase of 15 times in the adsorption capacity. The adsorption of RR141 on CS–APTES was favored at pH 3.0 using a dosage of 3.0 g L–1. The adsorption equilibrium was reached within 4 h, being the process thermodynamically favorable, endothermic, and controlled by chemisorption. The maximum adsorption capacity was 15.65 mg g–1. CS–APTES was efficient to treat a colored effluent containing various ions and molecules. The use of 10 g L–1 of CS–APTES was sufficient to decolorize more than 98% of this effluent. It was concluded that CS–APTES can be easily prepared from CS, generating an efficient and low-cost adsorbent which, in turn, is able to treat colored effluents

Current Applications of Recycled Aggregates from Construction and Demolition: A Review

A literature review comprising 163 publications published over a period of 26 years from 1992 to 2018 is presented in this paper. This review discusses the generation and recycling of construction and demolition waste (CDW) as well as its main uses as raw materials for the construction engineering sector. This review pays attention to the use of CDW aggregates for sand, pavements/roads, bricks, ceramics, cementitious materials, and concrete productions, as well its uses as eco-friendly materials for water decontamination. The physical-chemical and mechanical characteristics of recycled aggregates play an important role in their correctly chosen applications. The results found in this literature survey allow us to conclude that recycled aggregates from CDW can be successfully used to produce construction materials with quality comparable to those produced with natural aggregates. We concluded that the use of CDWs as raw materials for manufacturing new construction materials is technically feasible, economical, and constitutes an environmentally friendly approach for a future construction and demolition waste management strategy