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Residual biomass biochar for effective wastewater treatment of textile dye polluants
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Abstract(s)
A necessidade de desenvolver métodos sustentáveis e de baixo custo para o tratamento de
águas residuais, particularmente na indústria têxtil, que é um dos principais contribuintes
para a poluição da água, é de extrema relevância, visto que os métodos tradicionais para
remover corantes dos efluentes apresentam, frequentemente, um elevado custo, produzem
poluentes secundários e apresentam uma menor eficácia. Assim, os biocarvões oferecem
uma alternativa promissora devido à abundância de matérias-primas disponíveis, ao seu
baixo custo, e ao potencial de serem ajustados em função da aplicação pretendida. Dessa
forma, foram desenvolvidas diferentes amostras de biocarvões, derivadas de diferentes
resíduos agrícolas, como cascas de arroz, folhas de abacate, cascas de amendoim, e
misturas de macroalgas. As amostras de biocarvões foram produzidas através de pirólise a
350°C, sendo que a caracterização dessas amostras envolveu técnicas avançadas, como a
Difração de Raios X (XRD), Espectroscopia Raman e Análise Termogravimétrica (TGA).
Essas análises revelaram informações sobre a morfologia, grupos funcionais na superfície e
estabilidade térmica dos biocarvões, fatores cruciais que determinam a eficácia de cada
amostra, como adsorventes. Entre as amostras produzidas, o biocarvão de casca de arroz
(BRH) foi o que apresentou um desempenho superior no que toca à remoção de corantes,
alcançando uma capacidade de remoção de 99,2% para o corante Bezaktiv Blue HP-R,
81,4% para o Bezaktiv Red HP-R e 76,4% para o Bezaktiv Yellow HP-R. Para as misturas
de corantes, o BRH removeu 94,8% da mistura de corante verde e 100% da mistura de
corante roxo. O biocarvão de folhas de abacate (BAL) também demonstrou uma elevada
capacidade, especialmente na remoção de Bezaktiv Blue HP-R (94,8%) e Red HP-R
(83,6%). O biocarvão de casca de amendoim (BPS) apresentou desempenho variável, com
a maior eficiência para Bezaktiv Yellow HP-R (94%), mas com resultados inferiores para
outros corantes. Já o biocarvão de mistura de macroalgas (BMM) apresentou a menor
capacidade de remoção, particularmente para o corante Bezaktiv Yellow HP-R (58,2%) e o
Bezaktiv Red HP-R (69,1%). O bom desempenho do biocarvão derivado de cascas de arroz
(BRH), e do proveniente de folhas de abacate (BAL), pode estar relacionado com a sua área
de superfície, e com as interações que essas superfícies promovem. A amostra BRH, com
um alto teor de sílica e uma estrutura microporosa bem desenvolvida, oferece uma elevada
área de superfície e volume de poros, proporcionando dessa forma a capacidade de
adsorver moléculas de corantes, por intermédio de mecanismos como o preenchimento de
poros, ou através de interações eletrostáticas. A amostra BAL, por outro lado, é rica em
grupos funcionais fenólicos e álcoois, que contribuem para fortes interações de ligação de
hidrogénio e interações π-π com as moléculas dos corantes. Esses grupos funcionais,
juntamente com as estruturas aromáticas presentes no BAL, facilitam a formação de
complexos estáveis com os corantes, resultando em alta eficiência de adsorção.
The study is motivated by the urgent need for sustainable and cost-effective methods for wastewater treatment, particularly in the textile industry, which is a major contributor to water pollution. Traditional methods for removing dyes from effluents are often costly, generate secondary pollutants, and are less effective. Thus, biochar offers a promising alternative due to its abundant raw materials, cost-effectiveness, and potential to be tailored for specific applications. For that reason, distinct biochar samples were developed, derived from various agricultural wastes—namely rice husk, avocado leaves, peanut shells, and mixed macroalgae—as efficient sorbents for removing reactive dyes from wastewater. Biochar samples were produced via pyrolysis at 350°C, a process known to influence the physicochemical properties of the resulting material. The characterization of these biochars involved advanced techniques such as X-ray Diffraction (XRD), Raman Spectroscopy, and Thermogravimetric Analysis (TGA). These analyses revealed critical insights into the morphology, elemental composition, surface functional groups, and thermal stability of the biochars, which are crucial factors determining their effectiveness as adsorbents. Among the biochar samples, rice husk biochar (BRH) exhibited superior performance in dye removal, achieving removal efficiencies of 99.2% for Bezaktiv Blue HP-R, 81.4% for Bezaktiv Red HP- R, and 76.4% for Bezaktiv Yellow HP-R. For mixed dyes, BRH removed 94.8% of the Green dye mixture and 100% of the Purple dye mixture. Avocado leaves biochar (BAL) also demonstrated high efficiency, particularly in removing Bezaktiv Blue HP-R (94.8%) and Red HP-R (83.6%). Peanut shell biochar (BPS) showed a varied performance, with the highest efficiency for Bezaktiv Yellow HP-R (94%) but lower results for other dyes. Mixed macroalgae biochar (BMM) consistently displayed the lowest removal efficiency, particularly for Bezaktiv Yellow HP-R (58.2%) and Bezaktiv Red HP-R (69.1%). The superior adsorption performance of biochar derived from rice husk (BRH) and avocado leaves (BAL) can be attributed to their distinct surface properties and the specific interactions these surfaces promote. BRH, with its high silica content and well-developed microporous structure, provides extensive surface area and pore volume, enhancing its ability to adsorb dye molecules through mechanisms such as pore-filling and electrostatic interactions. Additionally, the alkaline nature of BRH due to its ash content likely increases the adsorption of anionic dyes by enhancing electrostatic attraction. BAL, on the other hand, is rich in phenolic and alcoholic functional groups, which contribute to strong hydrogen bonding and π-π interactions with the dye molecules. These functional groups, along with the aromatic structures present in BAL, facilitate the formation of stable complexes with dyes, leading to high adsorption efficiency.
The study is motivated by the urgent need for sustainable and cost-effective methods for wastewater treatment, particularly in the textile industry, which is a major contributor to water pollution. Traditional methods for removing dyes from effluents are often costly, generate secondary pollutants, and are less effective. Thus, biochar offers a promising alternative due to its abundant raw materials, cost-effectiveness, and potential to be tailored for specific applications. For that reason, distinct biochar samples were developed, derived from various agricultural wastes—namely rice husk, avocado leaves, peanut shells, and mixed macroalgae—as efficient sorbents for removing reactive dyes from wastewater. Biochar samples were produced via pyrolysis at 350°C, a process known to influence the physicochemical properties of the resulting material. The characterization of these biochars involved advanced techniques such as X-ray Diffraction (XRD), Raman Spectroscopy, and Thermogravimetric Analysis (TGA). These analyses revealed critical insights into the morphology, elemental composition, surface functional groups, and thermal stability of the biochars, which are crucial factors determining their effectiveness as adsorbents. Among the biochar samples, rice husk biochar (BRH) exhibited superior performance in dye removal, achieving removal efficiencies of 99.2% for Bezaktiv Blue HP-R, 81.4% for Bezaktiv Red HP- R, and 76.4% for Bezaktiv Yellow HP-R. For mixed dyes, BRH removed 94.8% of the Green dye mixture and 100% of the Purple dye mixture. Avocado leaves biochar (BAL) also demonstrated high efficiency, particularly in removing Bezaktiv Blue HP-R (94.8%) and Red HP-R (83.6%). Peanut shell biochar (BPS) showed a varied performance, with the highest efficiency for Bezaktiv Yellow HP-R (94%) but lower results for other dyes. Mixed macroalgae biochar (BMM) consistently displayed the lowest removal efficiency, particularly for Bezaktiv Yellow HP-R (58.2%) and Bezaktiv Red HP-R (69.1%). The superior adsorption performance of biochar derived from rice husk (BRH) and avocado leaves (BAL) can be attributed to their distinct surface properties and the specific interactions these surfaces promote. BRH, with its high silica content and well-developed microporous structure, provides extensive surface area and pore volume, enhancing its ability to adsorb dye molecules through mechanisms such as pore-filling and electrostatic interactions. Additionally, the alkaline nature of BRH due to its ash content likely increases the adsorption of anionic dyes by enhancing electrostatic attraction. BAL, on the other hand, is rich in phenolic and alcoholic functional groups, which contribute to strong hydrogen bonding and π-π interactions with the dye molecules. These functional groups, along with the aromatic structures present in BAL, facilitate the formation of stable complexes with dyes, leading to high adsorption efficiency.
Description
Keywords
Biocarvão Adsorção Tratamento de águas residuais Corantes reativos Sustentabilidade Biochar Adsorption Wastewater treatment Reactive Dyes Sustainability