Abstract
The prospect of synthesizing biochar from agricultural wastes or by-products to utilize them as a promising adsorbent material is increasingly gaining attention. This research work focuses on synthesizing biochar from castor biomass (CBM) and evaluating its potential as an adsorbent material. Castor biomass-based biochar (CBCs) prepared by the slow pyrolysis process at different temperatures (CBC400 °C, CBC500 °C, and CBC600 °C for 1 h) was investigated for the adsorption of textile dye effluents (safranin). The pyrolysis temperature played a key role in enhancing the morphology, and the crystallinity of the biochar which are beneficial for the uptake of safranin. The CBC600 adsorbent showed a higher safranin dye removal (99.60%) and adsorption capacity (4.98 mg/g) than CBC500 (90.50% and 4.52 mg/g), CBC400 (83.90% and 4.20 mg/g), and castor biomass (CBM) (64.40% and 3.22 mg/g). Adsorption data fitted better to the Langmuir isotherm model than to the Freundlich isotherm model. The kinetics of the adsorption process was described well using the pseudo-second-order kinetic model. The study on the effect of the contact time for the adsorption process indicated that for CBC600, 80% dye removal occurred in the first 15 min of the contact time. After three regeneration cycles, CBC600 exhibited the highest dye removal efficiency (64.10%), highlighting the enhanced reusability of CBCs. The crystalline patterns, functional binding sites, and surface areas of the prepared CBCs (CBC400, CBC500, CBC600) were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller surface area measurements, respectively.
Highlights
Licensee MDPI, Basel, Switzerland.Rapid population growth and industrialization have led to an increase in energy demands and environmental problems and reduced clean water sources [1,2]
The BET results indicate that the pyrolysis temperature has a strong influence on the surface area of the adsorbent
The application of a higher pyrolysis temperature and longer pyrolysis times resulted in biochars with a higher surface area and porosity [34]
Summary
Different physicochemical treatment processes have been applied to remove dyes from textile wastewater (TWW), such as adsorption ion exchange, reverse osmosis, precipitation, photodegradation, ozonation and other chemical oxidation, membrane bioreactors, electrolysis, electrodialysis, foam flotation, photocatalysis, and filtration [8] These treatment methods are expensive, have intricate designs, high capital costs, high maintenance costs, and high operating costs, and produce massive amounts of sludge that causes problems in being discarded [9]. The favourable properties exhibited by biochar including the high surface area, highly porous structure, hollow network structure, and enhanced ion exchange capacity make it an attractive choice for adsorption applications [24] These materials are considered heterogeneous carbon-based materials formed by the pyrolysis process in the absence of oxygen [26]. Sustainability 2021, 13, x FOR PEER REVIEW pyrolysis temperature on the morphology, crystallinity, surface area, and presence of functional groups
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