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Textile dyes are frequently disposable in aqueous effluents, making it difficult to remove them from industrial effluents before their release to natural waters. This paper deals with the fabrication of cellulose-based adsorbents by reacting nanocelulose crystalline (nanocel) with N-[3-(trimethoxysilyl)propyl]ethylenediamine (TMSPEDA), forming the hybrid (silylpropyl)ethylenediamine@nanocellulose (SPEDA@nanocel), which was employed as adsorbent for the uptake of reactive yellow 2 dye (RY-2) from aqueous effluents. Characterisation of SPEDA@nanocel was carried out using FTIR, SEM–EDS, XRD, TGA, surface area, pHpzc, and hydrophobicity/hydrophilicity ratio (HI). Also, adsorption studies were thoroughly investigated. The effect of initial pH indicated that the maximum uptake of RY-2 takes place at pH 2, which is an indication of the electrostatic mechanism. The kinetic data carried out with 250 and 500 mg L−1 RY-2 with SPEDA@nanocel followed better the nonlinear fractional-like pseudo-first-order model. The t0.5 and t0.95 for the dye uptake were about 30 and 141 min, respectively. The equilibrium data from 10 to 45 °C indicated that the Liu isotherm model was the best-fitted isothermal model. The maximum sorption capacity attained was 112.3 mg g−1 at 45 °C. The thermodynamic data have shown that the equilibrium was favorable and endothermic, and the ΔH° was compatible with an electrostatic attraction between RY-2 and SPEDA@nanocel. Experiments of desorption of loaded adsorbent showed promising results for real applications since at least 5 adsorption/desorption cycles could be employed without significant changes in the recovery and with high precision. [ABSTRACT FROM AUTHOR]

• Sustainable strategy to synthetize selenium-doped biochar materials. • High surface area Se-doped biochar (1300 m2/g) with mesopore features was synthetized. • Selenium-doped biochar showed effective removal of selected dye and drug. • High-performance adsorbents for treating different synthetic effluents. In this study, for the first time, a selenium-doped mesoporous biochar was prepared and efficiently employed for sodium diclofenac and reactive orange 16 dye adsorption. The characterization results indicated that selenium doping had a remarkable impact on Biochar-Se morphological and physicochemical structures. The efficacy of developed biochar samples on reactive orange 16 (RO-16) and diclofenac (DCF) removals was fully investigated. For both molecules (DCF and RO-16), Liu's equilibrium model offered the best fitness with maximum adsorption capacity values of 355 mg g−1 for DCF and 538 mg g−1 for RO-16 for Biochar-Se. Multiple mechanisms including pore filling, π-π interaction, and hydrogen bonding between the Biochar-Se and DCF/RO-16 molecules were involved in the adsorption process. Se-nanoparticles formed metal–oxygen bonds, which boosted the adsorption of DCF and RO-16 molecules. The current work offered a feasible approach for the development of Se-doped biochar adsorbent that is incredibly effective in treating wastewater. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Green strategy for developing advanced heteroatom-doped biomass-derived carbon materials. • Nitrogen doping strategy boosted the number of functionalities on the biochar surface. • Nitrogen doping boosted dye adsorption capacity due to the multiple mechanisms. [ABSTRACT FROM AUTHOR]

Alternative treatments, such as, NaOH, ultrasound assisted (UA) and supercritical CO2 (SCO2), were performed to improve the potential of rice husk as adsorbent to remove methylene blue (MB) from aqueous media. All the treatments improved the surface characteristics of rice husk, exposing its organic fraction and/or providing more adsorption sites. The Langmuir and Hill models were able to explain the MB adsorption for all adsorbents in all studied temperatures. The experimental and modeled parameters demonstrated that the MB adsorption was favored by the temperature increase and by the use of NaOH-rice husk. The maximum adsorption capacities for the MB solutions (ranging from 10 to 100 mg L-1), estimated from the Langmuir model at 328 K, were in the following order: NaOH rice-husk (65.0 mg g-1)>UA-rice husk (58.7 mg g-1)>SCO2-rice husk (56.4 mg g-1)> raw rice husk (52.2 mg g-1). The adsorption was a spontaneous, favorable and endothermic process. In general, this work demonstrated that NaOH, UA and SCO2 treatments are alternatives to improve the potential of rice husk as adsorbent. [ABSTRACT FROM AUTHOR]

Textile dyes are one of the most commonly found pollutants in water, and it is necessary to remove them before textile industry effluents are released into the environment. In this study, cellulose-based adsorbents were prepared by grafting N1-(3-trimethoxysilylpropyl)-diethylenetriamine (TMSPDETA) on microcrystalline cellulose surface for the adsorption of reactive dyes from aqueous solution. Characterization of the produced adsorbents [Cel@TMSPDETA 10 ; composite of cellulose + TMSPDETA (10% weight)] and the experimental and modeling studies were thoroughly investigated. Based on ΔBIC analysis (Bayesian Information Criterion), the fractal-like pseudo-first-order model (FPFO) was the model with the highest degree of adequacy to describe the kinetic behavior for RR-35 (Reactive Red 35) and RG-19 (Reactive Green 19) dye adsorption on Cel@TMSPDETA 10. It was observed that the values of t 0.95 (time necessary to attain 95% saturation) of RG-19 dye were 1.81 times slower than those of RR-35. This difference in times to attain 95% saturation of RG-19 with RR-35 could be assigned to the larger size of the RG-19 molecule. Based on the ΔBIC values, the Liu isotherm was better fitted to the experimental data. At 30 °C, the highest Q max (Liu model) value was 197.0 mg g−1 for RR-35 dye. For RG-19, the highest value of Q max (Liu model) was 210.5 mg g−1 at 45 °C. Alternatively, a statistical physics model that represents the general case of the Langmuir model was adopted to provide new insights into the adsorption mechanisms of RR-35 and RG-19 dyes on the adsorbents. Interestingly, this new approach showed that RR- 35 was adsorbed via a partial aggregation process, contrary to the RG-19 dyes. [Display omitted] • Increase in the sorption capacity of up to 8 times Cel@TMSPDETA 10 to Cel • Cel@TMSPDETA 10 was employed to remove RR-35 and RG-19 dyes from wastewater. • The FPFO and Liu models were fitted to describe the kinetic and equilibrium experiments. • Statistical physics data shows that RR-35 was adsorbed with a lower aggregation degree. • Statistical physics data shows that RG-19 was adsorbed with a higher aggregation degree. [ABSTRACT FROM AUTHOR]