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This study aims to investigate the use of rubber (Hevea brasiliensis) seeds, a solid agricultural waste, as a novel adsorbent for the adsorption of Congo red (CR) from aqueous solution in batch mode. Experiments were carried out as a function of contact time, dye concentration, adsorbent dosage, pH, and temperature. Langmuir, Freundlich, and Sips adsorption isotherm models were applied to describe isotherm parameters. The results showed that equilibrium contact time was 90 min. The experimental results indicate that, the percentage of dye adsorption increases with an increase in the adsorbent dosages and temperature. The CR adsorption percentage decreased with increasing dye concentration and pH solution from 3 to 12. Thermodynamic parameters data indicated that the CR adsorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (∆G°) in the range of 9.13–8.12 kJ/mol, enthalpy (∆H°) and entropy (∆S°) of 14.15 kJ/mol and 16.85 J/mol, respectively. The Langmuir isotherm model fit the equilibrium data better than both the Freundlich and Sips isotherm models, with adsorption capacity 9.82 mg/g. The kinetic data for adsorption processes were described by pseudo-second-order model with a rate constant in the range of 0.043–0.156 g mg/g min−1. The rubber seeds investigated in this study showed a high potential use for the adsorption of CR from aqueous solution. [ABSTRACT FROM AUTHOR]

The sorption of lignosulfonate onto powdered eggshell under the influence of temperature has been studied. The rate of adsorption onto eggshell was investigated under a variety of adsorbent dosages. The kinetic data from these investigations were correlated to a number of adsorption models in an attempt to elucidate the mechanism of the adsorption processes. Thermodynamic parameter data indicated that the lignosulfonate sorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (ΔG°) in the range of 1.83-1.07 kJ mol-1, enthalpy (ΔH0) and entropy (ΔS0) of 5.66 kJ mol-1 and 12.82 J mol-1, respectively and the activation energy of 18.17 kJ mol-1. The adsorption mechanism was found to follow a pseudo-second-order model, with the kinetic constants in the range of 0.689-1.430 g mg-1 min-1. Both the intra-particle diffusion and Boyd kinetic models indicated that boundary layer/film diffusion was the main rate determining step in lignosulfonate adsorption process. [ABSTRACT FROM AUTHOR]

In this study, TiO2/ZnO nanocomposite (TZC) photocatalysts were successfully prepared through a sol-gel process followed by calcination. TZC photocatalyst characterization was performed by XRD, FTIR, SEM, TEM and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the TZC photocatalyst is studied systematically by the degradation of humic acid (HA) from aqueous solutions under visible light irradiation. Photodegradation of HA from aqueous solutions shows excellent photocatalytic activity. The rate of photocatalytic degradation increases with increasing catalyst loading and light intensity. From kinetic studies, it showed that HA photodegradation using TZC photocatalysts can be explained by the pseudo-firstorder kinetic model. The results also show that this method has excellent potential to remove HA from peat water. [ABSTRACT FROM AUTHOR]

The foremost objective of this work is to prepare a novel electrochemical sensor-based screen-printed carbon electrode made of zinc oxide nanoparticles/molecularly imprinted polymer (SPCE-ZnONPs/MIP) and investigate its characteristics to detect sodium dodecyl sulfate (SDS). The MIP that is polyglutamic acid (PGA) film was synthesized via in situ electro-polymerization. The SDS's recognition site was left on the surface of the PGA film after extraction using the cyclic voltammetry (CV) technique, facilitating the specific detection of SDS. Moreover, the ZnONPs (∼71 nm, polydispersity index of 0.138) were synthesized and effectively combined with the MIP by a drop-casting method, enhancing the current response. The surface of the prepared SPCE-ZnONPs/MIP was characterized by scanning electron microscopy and energy dispersive X-ray. Besides, the electrochemical performance of the SPCE-ZnONPs/MIP was also studied through CV and differential pulse voltammetry (DPV) techniques. As an outstanding result, it is observed that the current response of SPCE-ZnONPs/MIP for detection of SDS remarkably increased almost four times higher from 0.009 mA to 0.041 mA in comparison with bare SPCE. More importantly, the proposed SPCE-ZnONPs/MIP exhibited an excellent selectivity (in the presence of interfering molecules of Ca 2+ , Pb 2+ , as well as sodium dodecylbenzene sulfonate (SDBS)), sensitivity, reproducibility, and repeatability. Since the modified sensor offers portability, it is suitable for in situ environment and cosmetic monitoring., Competing Interests: There is no conflict to declare., (This journal is © The Royal Society of Chemistry.)