In this work, activated carbons (ACs) prepared by chemical activation of garcinia cola nut shell impregnated with H 3 PO 4 (CBH 2/1) and KOH (CBK 1/1) were used to study the kinetics, equilibrium and thermodynamics of the adsorption of thymol blue from aqueous solution. The characterization of ACs showed the BET measurements gave surface area and total pore volume respectively of 328.407 m 2 •g −1 and 0.1032 cm 3 •g −1 for CBH 2/1 and 25.962 m 2 •g −1 and 0.03 cm 3 •g −1 for CBK 1/1 ; elemental analysis showed a high percentage of carbon in both ACs. Influence of parameters such as initial pH, contact time, adsorbent mass, initial concentration, ionic strength and the effect of temperature on the removal of thymol blue from aqueous solution were studied in batch mode. The studies showed that equilibrium adsorption was attained after 60 minutes for the two ACs, adsorption capacity increased with increasing concentration of thymol blue, and maximum adsorption capacity was obtained at an acidic environment with pH 2. Avrami's non-linear kinetic expression was the best suited for describing the adsorption kinetics of thymol blue onto ACs, while equilibrium data showed that the three-parameter isotherms better described the adsorption process since R 2 > 0.96, and the error functions were lowest for all of them.

A simple and fast electrochemical method based on aminoalcohol-functionalized palm oil fiber modified carbon paste electrode (TEA-POF/CPE) has been used for the electroanalysis of 2-nitrophenol (2-NP). The aminoalcohol-functionalized palm oil fiber (TEA-POF) was prepared by chemical grafting of triethanolamine (TEA) onto the surface of alkali material. The grafted material was characterized by some physico-chemical techniques. The electrochemical results showed that the TEA-POF/CPE exhibited more sensitive response towards the 2-NP reduction and allowed to estimate a low detection limit of 1.26 μM (S/N = 3). Finally, the sensor has been selective and successfully applied to the 2-NP detection in real water samples.

In the present work, the usefulness of cetyltrimethylammonium bromide-modified palm oil fiber (CTAB-modified POF) for the removal of indigo carmine (IC) and 2,6-dichlorophenolindophenol (2,6-DCPIP) from aqueous solutions was investigated. Raw, NaOH-treated, and CTAB-modified POF were characterized by Fourier-transform infrared (FT-IR) spectroscopy, elemental analysis, thermogravimetric-hyperdifferential scanning calorimetric (TG-HDSC) analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). e adsorption studies of IC and 2,6-DCPIP were performed in batch mode using CTAB-modified POF. e results showed that equilibrium was attained after a contact time of 30 minutes for IC and 20 minutes for 2,6-DCPIP. e maximum capacity of adsorption was obtained at pH � 2. e capacity of adsorption considerably increased with modified biosorbents and with increasing initial concentration of dyes. e ionic strength favors the increasing adsorption capacity of IC and does not affect the adsorption capacity of 2,6-DCPIP. e percentage of adsorption increased with increasing mass of the biosorbents. e nonlinear regression of adsorption isotherms showed that Freundlich (r 2 � 0.953; χ 2 � 4.398) and Temkin (r 2 � 0.986; χ 2 � 1.196) isotherms are most appropriate to describe the adsorption of IC and 2,6-DCPIP on CTAB-modified POF, respectively. e maximum adsorption capacities determined by the Langmuir isotherm were 275.426 and 230.423 μmol·g − 1 for IC and 2,6-DCPIP, respectively. e linear regression of adsorption kinetics was best described by the pseudo-second-order model (R 2 ≥ 0.998). e diffusion mechanism showed that external mass transfer is the main rate controlling step. Desorption of the two dyes is favorable in the alkaline medium.

This work describes a new sensitive sensor for the simultaneous electrochemical determination by square wave anodic stripping voltammetry of Cd 2+ and Pb 2+ ions in aqueous solution, based on a disposable ink-jet-printed graphene electrode (IPGE) modified by a thin film of montmorillonite (Mont) clay mineral. The clay was characterized by X-ray diffraction and scanning electron microscopy while the Mont-IPGE was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry before its exploitation for sensing studies. EIS results revealed a low electron transfer rate on Mont-IPGE during the electro-oxidation of [Fe(CN) 6 ] 3−. The stripping response on both Cd 2+ and Pb 2+ analytes was improved by the in situ co-deposition with bismuth, added to the electrolyte solution, on the clay substrate. The proposed electrode showed great stability and good reproducibility. The key experimental parameters governing the stripping analysis of Cd 2+ and Pb 2+ were optimized. A linear relationship between peak currents and concentrations of the analytes was obtained in the range from 0.01 to 0.21 µM, leading to detection limits of 0.42 nM for Cd 2+ and 1.14 nM for Pb 2+ ions, respectively (S/N = 3). The sensitivities to Cd 2+ and Pb 2+ ions were 921.8 A cm −2 M −1 and 1960.8 A cm −2 M −1 , respectively. The Mont-IPGE sensor was used for the quantification of lead and cadmium in a mineral water.

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