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In this research, the greener catalyst of iron nanoparticles (G-FeNPs) was synthesized from the reduction of iron (III) salt by the extract of used green tea leaves waste. The product was characterized by SEM, AFM, and FTIR, while the zeta potential was measured to study the stability of G-FeNPs. The degradation of the anionic dye Eriochrome Blue Black R (EBBR) from an aqueous solution using a Fenton-like process catalyzed by G-FeNPs has been studied. The effects of catalyst dosage, hydrogen peroxide concentration, and pH, initial concentration of EBBR dye, contact time, and temperature were studied and evaluated for dye degradation. The optimized conditions achieved 91.5% removal of 25 mg/L EBBR dye at the reaction conditions: [G-FeNPs] = 0.8 g/L, [H2O2] = 4 mmol/L, pH=3, 60 min contact time, and at room temperature. Four kinetic models were employed to study the reaction kinetic model favorable; first-order, second-order, Elovich, and Behnajady-Modirshahla-Ghanbary (BMG). In general, Elovich and BMG reaction kinetics models are well fitted to all reactions. The thermodynamic functions, such as ΔGº, ΔHº, and ΔSº, were also investigated. The results obtained indicate that the Fenton-like process of EBBR dye was spontaneous and endothermic.

Most of dyes cause various environmental and health problems due to their toxic, mutagenic, and even carcinogenic properties. Therefore, several treatment methods are used to remove dyes from wastewater. Adsorption is one of the most preferred methods due to its easy application and high efficiency. The aim of this study is to prepare and characterize KOH-activated pine cone (APC) biochar and use it as adsorbent for removal of anionic diazo dye, Congo red (CR) from aqueous solution. The various operating parameters such as pH, contact time, temperature, initial dye concentration, and adsorbent dosage are optimized in batch adsorption system. Experimental results showed that the prepared APC biochar has a surface area of 1714.5 m2/g and was achieved 94.62% CR removal efficiency at an adsorbent dosage of 2 g/L. The Freundlich, Langmuir, and Temkin adsorption models were used for the mathematical description of the adsorption equilibrium. Experimental data showed the best compatibility with the Freundlich isotherm. Batch adsorption models, based on the assumption of the pseudo first-order, pseudo second-order, and intra particle diffusion mechanisms, were applied to examine the kinetics of the adsorption. Kinetic data fitted the pseudo second-order kinetic model. Calculated thermodynamic parameters indicated the spontaneous, endothermic, and the increased randomness nature of CR adsorption. Structural and morphological changes of APC biochar after adsorption process were determined by using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis. The prediction of the CR adsorption capacity of the APC biochar using artificial neural network (ANN) algorithm was modeled. For this purpose, many different ANN models have been developed. Among them, ANN10 gave the best results. According to ANN10 results, root-mean-squared error (RMSE), mean bias error (MBE), mean absolute error (MAE), and correlation coefficient (R2) were estimated as 0.770, 0.310, 0.037, and 0.999, respectively. Consequently, the prediction results showed well agreement with experimental results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cheap, novel, ecofriendly and effective nanosorbent was engineered. • A comprehensive study has been done for adsorption and determination of thiophene. • Determination of thiophene was done by UV–Vis spectroscopy at 222 nm. • The results were checked with spike recovery test and direct GC-FID method. In this study, an engineered Fe 3 O 4 @SiO 2 -SH core–shell was synthesized as a novel, selective, efficient, cost-effective, and magnetic nanosorbent from natural materials such as sea sand and rice husk. TEM, FE-SEM, EDX, XRD, TGA, VSM, BET, and FTIR were used for the characterization of nanosorbents. A comprehensive study has been done for the adsorption and determination of thiophene as an important sulfur-containing aromatic petroleum contamination. Adsorption isotherms, kinetics and thermodynamics were also studied. Determination of thiophene was done by UV–Vis spectroscopy at 222 nm. The effective parameters in the separation and determination of thiophene were optimized. The detection limit of the method is equivalent to 88 µg/L and the dynamic linear range is in the range of 800 to 19200 µg/L. Based on the Langmuir isotherm, the maximum absorption capacity for the nanoabsorbent is 204.08 mg/g. River water, textile factory effluent, and oil refinery effluent were successfully applied as the real samples for separation and determination of thiophene. The results were checked with spike recovery test and direct measurement gas chromatography method. The statistical analysis shows a good agreement between the results of the two methods. [ABSTRACT FROM AUTHOR]

The effect of the surface topography on protein adsorption process is of great significance for designing hydroxyapatite (HA) ceramic material surfaces. In this work, three different topographies of HA materials HA-sheet, HA-rod, and HA-whisker were synthesized and testified by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Brunauer–Emmett–Teller (BET) and a field emission scanning electron microscopy (FE-SEM). We have systematically investigated the adsorption kinetics and thermodynamics of bone morphogenetic proteins (BMP-2) on the three different topography surfaces of HA, respectively. The results showed that the maximum adsorption capacities of HA-sheet, HA-rod and HA-whisker were (219.96 ± 10.18), (247.13 ± 12.35), and (354.67 ± 17.73) μg · g − 1 , respectively. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated as well as discussed. It demonstrated that the adsorption of BMP-2 onto HA could be described by the pseudo second-order equation. Adsorption of BMP-2 onto HA followed the Langmuir isotherm. It confirmed that compared with other samples HA-whisker had more adsorption sites for its high specific surface area which could provide more opportunities for protein molecules. The adsorption processes were endothermic (Δ H > 0), spontaneous (Δ G < 0) and entropy increasing (Δ S > 0). A possible adsorption mechanism has been proposed. In addition, the BMP-2 could be adsorbed to the surface which existed slight conformational changes by FT-IR. [ABSTRACT FROM AUTHOR]

Abstract: In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic. [Copyright &y& Elsevier]

Developing cost- effective green sorbents for enhanced removal of organophosphorus pesticides from contaminated water remains inspirational. In this study, a novel nanoscale Moringa olivera seeds waste (nMSW) was produced and applied for the first time as an effective bio-nanosrbent for chlorpyrifos (CPF) removal from contaminated wastewater. The nMSW sorbent was characterized and the parameters that affect the biosorption process like CPF concentration (10–80 μg/mL), biosrbent dose (0.05–0.5 g), solution pH (5–9), exposure time (10–1440 min) and temperature (25–45 °C) were optimized. The CPF adsorption by nMSW follows in order Langmuir >Temken >Kiselev adsorption models. The maximum adsorption capacity of nMSW for CPF has shown 2.75 folds increase (25 mg g−1) compared to that of the conventional bulk MSW and superior to most of the reported green sorbents. The sorption kinetics data fitted well to the power function and first-order models. Remarkable CPF removal efficiency of 81% was achieved using nMSW at pH 7 in contact time period of 30 min. The thermodynamic parameters revealed the spontaneous and the exothermic nature of CPF sorption process. The functional groups of nMSW and CPF, thermodynamics and bio-sorption data suggested that H-bonding, hydrophobicity, electrostatic and π–π interactions are the main driving forces in CPF removal mechanism by nMSW. The novel nano-biosorbent can be introduced as an effective green and low cost alternative for CPF removal from contaminated wastewater. [Display omitted] • Utilization of Moringa seed waste for production of a novel nano-sorbent. • Nano-sized Moringa oleifera seed waste greatly enhanced chlorpyrifos adsorption. • Adsorption of chlorpyrifos was a spontaneous and exothermic process. • Mechanism of chlorpyrifos adsorption is facilitated by H-bonding and hydrophobicity. [ABSTRACT FROM AUTHOR]