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

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

PRODUÇÃO DE CARVÃO ATIVADO A PARTIR DE LODO DE ESGOTO DOMÉSTICO E SUA APLICAÇÃO NA ADSORÇÃO DO CORANTE PRETO REMAZOL 5 EM SOLUÇÃO AQUOSA

O presente estudo investigou a viabilidade do lodo de esgoto como matéria- prima para produção de carvões ativados (CAs) para remoção do corante preto remazol 5 de soluções aquosas. Duas amostras foram preparadas; um carvão quimicamente ativado com ZnCl2 denominado CAZ e um carvão ativado sem ativação química denominado CA. Os CAs foram caracterizados por adsorção/dessorção de N2, área superficial especifica SBET e Microscopia eletrônica por varredura (MEV). De acordo com os resultados obtidos pelas isotermas de N2 os carvões foram classificados como mesoporosos, no entanto a amostra CAZ apresentou elevado valor de BET comparado ao carvão CA, 612 e 21,8 m2g-1, respectivamente. A habilidade dos CAs na remoção do corante RB-5 foi investigado empregando processo de adsorção em batelada. Os dados de equilíbrio foram ajustados aos modelos de isotermas de Lagmuir, freundlich e Sips. Levando em conta os valores de R2 e função erro (SD), os dados foram melhores ajustados à isoterma de Sips. A capacidade máxima adsorvida do corante RB-5 sobre os carvões CA e CAZ foram de 16.12 e 156.64 mgg-1, respectivamente.AbstractThe present study investigated the feasibility of sewage sludge as raw material for production of activated carbon to remove Remazol Black 5 dye from aqueous solutions. Two activated carbons were prepared; activated carbon chemically with ZnCl2 named CAZ and activated carbon without activation named CA. The adsorbents were characterised using N2 adsorption/desorption isotherms, specific surface area (SBET) and scanning electron microscopy. According to the N2 isotherms both samples were characterised as mesoporous activated carbons, however the sample ACZ presented higher SBET compared to the sample CA, 612 and 21,8 m2 g -1 , respectively. The ability of activated carbons to remove the RB-5 was investigated using batch adsorption procedure. The equilibrium data were fitted to Langmuir, Freundlich and Sips isotherm models. Taking into account the determination coefficient (R2 ) and error function (SD), the data were best fitted to Sips isotherm model. The maximum adsorption capacities of RB-5 onto AC and ACZ are 16.12 and 156.64 mgg -1 , respectively

Some observations on the influence of particle size and size distributionon stratification in pneumatic jigs

Particle size variation plays a key role in jigging performance, and despite extensive research in the area, very little attention has been given in the case of pneumatic jigging. The aim of this study was to look into particle stratification in a pilot-scale pneumatic jig when varying the particle size and the range of the particle size distribution in ternary mixtures of aggregates. Jigging tests were especially designed to reduce contamination of jig products and a stratification index was elaborated to evaluate stratification efficiency. Experimental results provided compelling evidences that widening the particle size distribution of the system or using beds composed of particles of smaller sizes can enhance stratification by density. Similarly, smaller particles showed a remarkable tendency to concentrate in the upper zones of the stratified bed, whereas larger particles tended to concentrate more in lower zones. The obtained results suggest that particular operating features of pneumatic jigging together with differential packing effects should play a decisive role in the stratification extent of beds formed by particles of different sizes. Experimental results are of practical importance since, among other benefits, they point to the possibility to increase pneumatic jigging performance in some cases by using wider size distributions of the feed, thus reducing the need of prior stages of narrow size classification

Preparation of highly porous nitrogen-doped biochar derived from birch tree wastes with superior dye removal performance

Heteroatom doping is a highly effective strategy that can be used to modify carbonaceous adsorbents to improve their chemical reactivity and increase their adsorptive properties. Herein, a simple method is reported for the preparation of nitrogen-doped biochar using a natural and abundant biowaste from birch trees and melamine as a nitrogen dopant for the adsorption of Acid red 18 (AR-18) dye from water. The doped biochars were also characterized for their performance during the treatment of synthetic effluents. The physicochemical characterization results showed that the N-doping process provoked remarkable chances on the biochar morphology, pore structure, and surface functionalities. N-doped biochar showed abundant nitrogen functional groups with 5.4 % of N in its structure while non-doped carbon showed traces with 0.47 %. Moreover, the specific surface area of doped biochar was dominated by mesopores (86.4 %) while non-doped was dominated by micropores (67.8 %). Raman analysis showed that the incorporation of N created more defects in the biochar structure. The adsorption experiments showed that the N-doping boosted the biochar adsorptive performance. The maximum adsorption capacity of the doped biochar was 545.2 mg g−1, while the non-doped exhibited 444.5 mg g−1, i.e., an increase of 22.6 %. The kinetic and equilibrium studies showed that Avrami fractional order and Liu models were the most suitable for describing the experimental AR-18 dye adsorption data. The equilibrium parameters were found to obey a nonlinear relationship with the temperature. Since the biochars are highly porous, pore filling was the main adsorption mechanism, however; AR-18 dye removal suggests that interactions such as electrostatic, hydrogen bonds, Lewis acid-base, and π-π between the adsorbent and the dye are involved. The thermodynamic studies showed that the removal of the AR-18 dye from the solution is dependent on temperature, exothermic, and spontaneous. The N-doped biochar showed excellent removal performances of contaminants from synthetic effluents confirming their high efficiency for color removal. This research shows that N-doping is an efficient strategy to design effective, low-cost, and sustainable adsorbents to remediate dye contamination in wastewater

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

Coupling of attrition and accelerated carbonation for CO2 sequestration in recycled concrete aggregates

Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (published version