Oranges are popularly consumed globally because of their high nutritional values and antioxidant properties. The leftover orange wastes, readily available as a raw material, can be effectively utilized to produce adsorbents and catalysts that can scavenge and break down a diverse spectrum of pollutants from aqueous solutions. This study explores the potential use of orange waste as a raw material for the preparation of an adsorbent to remove heavy metals, dyes, pesticides, herbicides, polycyclic aromatic hydrocarbons (PAHs), aromatic hydrocarbons, inorganic contaminants, and radioactive ions from water. Additionally, it explores the use of orange waste in treating gaseous pollutants and preparing catalysts for degrading dye, pharmaceutical, and plastic pollutants. Recent research has focused on developing low-cost adsorbents from orange waste and studying its isotherms, kinetics, and thermodynamic properties against pollutants. Critical discussions have been conducted on the isotherm model, kinetic model, and thermodynamic parameters calculations for orange waste-derived adsorbents. Conclusions are drawn from the data presented in the preponderance of published articles on the use of orange waste-derived materials against environmental pollutants. There is a lack of comprehensive review articles on the adsorption and catalytic properties of orange waste-derived materials against various contaminants. Recent research has demonstrated that orange waste could serve as a potential eco-friendly material for the remediation of environmental pollutants.

This study explored the fabrication of activated carbon from teff husk biomass using microwave and mufflefurnace -assisted heating and observed its effect on surface characteristics and the thermodynamics, isotherm, and kinetics of Pb2+ ions removal. Chemical activation of the teff husk was carried out using ZnCl2 as an activating agent. The microwave -assisted activated carbons (MW-THAC) and muffle furnace -assisted activated carbon (MF-THAC) were characterized for surface area, pHzpc, functional groups, thermal stability, phase composition, surface morphology, and surface -elemental compositions. The surface area of MW-THAC and MFTHAC was found to be 9.81 m2/g and 327.54 m2/g, respectively. Thermodynamic parameters indicated that the interaction with MW-THAC and MF-THAC was spontaneous and endothermic. The maximum Pb adsorption capacities of MW-THAC and MF-THAC calculated using the Langmuir model at 45 degrees C were found to be 20.45 mg/ g and 26.04 mg/g, respectively. Pb2+ removal through MW-THAC followed the Langmuir isotherm and the pseudo -first order kinetic model. However, the Freundlich isotherm and pseudo -second order kinetic models best describe Pb2+ adsorption onto the MF-THAC surface. The desorption study shows that 80.6 % and 78.7 % of Pb2+ ions can be recovered from the surfaces of the MW-THAC and MF-THAC adsorbents. This study confirms that activated carbon derived from teff husk could be a potential candidate for the adsorption and recovery of Pb2+ ions.

The quality of drinking water in Ethiopia is an influential environmental factor of health and water can use as a medium for disease transmission in countries on all continents; all are affected from the poorest to the richest. Moreover, in our globe millions of people are unprotected to unsafe concentration of chemical pollutants in the drinking water. Dichlorohenols are considered as key water pollutants that are destructive to creatures at stumpy concentrations and many of them have been clustered as detrimental pollutants because of their probable to damage human health even in low concentration. This research aimed to determine phenolic compounds from drinking water of Jimma town which is found south west of Ethiopia, by using 4-Aminoantipyridine (AAP). The sample of drinking water before and after treatment was collected for determination of pollutants which classified as raw water (RW), treated water (TW) and system distributed water (SDW). The sample of water was preserved by phosphoric acid and sulfuric acid under pH 4 and distillation was carried out in order to remove sulfur containing compounds by addition of CuSO4 solution. In the analysis of water using 4-Aminoantipyrine the treated water and the system distributed water have been contained 2.73 ppb and 3.64 ppb which had more phenolic compounds as compared to raw water of 1.18 ppb. Therefore, the existence of phenolic compound in both treated and system distributed water of Jimma town drinking water has more phenolic compounds as compared to the permissible level of both Ethiopian Standard, 2 ppb and EPA Standards, 1 ppb.

Present study discusses the removal of heavy metal contaminants from an aqueous solution using ortho-phosphoric acid activated pumpkin seed shells derived activated carbon (PSS-AC). The activation was done by heating the mixture in an electrical furnace at 800 °C for 3 h. Adsorption experiments were carried out as a function of pH, contact time, initial Cu (II) and Cd (II) ion concentrations, adsorbent dosage and temperature of the solution for the metal ion removal. The equilibrium and kinetic studies data were fitted better for the Langmuir isotherm model and pseudo-second order model respectively. Thermodynamic parameter obtained for Cu (II) and Cd (II) ions adsorption suggests the reaction to be non-spontaneous, feasible; and endothermic between temperatures of 25 °C and 45 °C.

Phenol compounds found in wastewaters of various industries such as petroleum refining, coal conversion, plastic, textiles, iron and steel manufacturing units.Remediation of phenols and its derivatives from contaminated water before discharging is essential, as they are toxic for aquatic organisms.This work is an attempt to remove phenol from aqueous solution applying the adsorption technique using locally available and eco-friendly tea waste adsorbent.The batch adsorption experiment was performed on different concentrations.Langmuir and Freundlich isotherms were applied to confirm the adsorption model.The data obtained found to be best fitted to the Langmuir isotherm.The kinetic study for the adsorption process were performed by checking various models and the data obtained show that the pseudo-second-order model fit well for both 8-HQ treated and untreated powdered tea waste adsorbent.

The locally available adsorbent pine apple peel ( Ananascosmosus ) has been tested by preparing activated carbon by KOH activation for its effectiveness in removing hexavalent chromium and divalent lead present in the water at low concentrations. Batch adsorption method has been employed to investigate the efficiency of the adsorbent. Adsorption parameters like adsorbent dose, p H, contact time and temperature have been obtained. Adsorption isotherms Freundlich and Langmuir, which states that heterogeneity of the adsorbent surface, were tested and the data obtained best fits to Freundlich model. The adsorption kinetics follow pseudo-second-order kinetic model. Thermodynamic parameters for Pb (II) and Cr (VI) adsorption, enthalpy change, (-0.149 and -0.081kJ/mol), entropy change (0.183 and 0.012kJ/mol), and Gibbs free energy change (-3.138 and -3.554 kJ/mol at 293 K, -3.191 and -3.615 kJ/mol at 298 K, -3.245 and -3.675 kJ/mol at 303 K), respectively have been calculated. The results show that adsorption is feasible, spontaneous in nature, and exothermic.

This paper mainly explain the lowering of band gap energy of synthesized ZnO nanoparticles (3.263eV) than their bulk counterparts (3.37 eV), which indicate the high conductivity than the bulk ZnO powder. Zn1-xLixO, Zn1-xNaxO and Zn1-xKxO (where x= 0.005, 0.01, 0.015 and 0.02 M for all dopants) doped ZnO nanoparticles and their solution was then characterized by UV-vis spectrophotometer. All concentration of Li + doped ZnO nanoparticles was more narrowing the band gap of the undoped ZnO nanoparticles than Na + and K + doped ZnO nanoparticles. Both the size and concentration of dopants were affecting the band gap energy of ZnO nanoparticles. As the concentration and ionic radii of the dopants increases the optical band gap energy was also increasing. So the highest band gap energy was obtained by 0.015 and 0.02M K + doped ZnO nanoparticles. © 2016 Elixir all rights reserved. Elixir Materials Science 91 (2016) 38058-38062 Materials Science Available online at www.elixirpublishers.com (Elixir International Journal) Tizita Girma et al./ Elixir Materials Science 91 (2016) 38058-38062 38059 Instrument and materials Analytical balance, Oven, Volumetric flask, Measuring cylinder, Ultrasonic wave irradiation, Quartz cuvett, Hot plate and JENWAY 6705 UV-visible spectrophotometer

This study was aimed for removal of phenol from water using activated carbon synthesize from avocado kernel seeds by adsorption onto it. For adsorption process cleaned and washed avocado kernel seeds ( Persea americana ) were dried at 100°C in an oven overnight and carbonization was carried out by increasing the furnace temperature at a rate of 5 °C/min to a final temperature of 800 °C for 160 minutes. Then, the activated carbon was powdered and sieved, washed with distilled water until the solution pH reached 7.0. Optimization of activated carbon was performed through effects of solution pH, contact time; initial phenol concentration and temperature of the adsorption. The kinetic studies of the adsorption process were achieved by verifying various models and the data obtained was best fitted to pseudo-second-order kinetic model. The isotherms models were analyzed with Langmuir, Freundlich and Temkin to validate the adsorption process. It was found that Langmuir model was best fitted to the obtained result for both adsorbents.

This study reports on the adsorption of 2-chlorophenol from an aqueous solution using activated carbon prepared by H2SO4 activation of the pericarp of Ricinus communis (RCAC). The pericarp was carbonized and activated by treating with H2SO4 solution followed by heating in an oven at 105 degrees C for 12 hrs. Batch adsorption experiments were carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature of the solution. Kinetic data were best fit to a pseudo-first-order rate equation for the adsorption of 2-chlorophenol on RCAC. Thermodynamic parameters H-o, S-o and G(o) for the adsorption were also determined which shows that adsorption on the surface of RCAC was spontaneous in nature, and exothermic between temperatures of 20 degrees C and 80 degrees C. The equilibrium data better fit the Langmuir isotherm model for 2-chlorophenol adsorption on RCAC. IR spectrum for loaded and unloaded RCAC was obtained and found to be in good agreement.

Adsorption of 8-hydroxyquinoline (8HQ) on powdered orange peel (POP), a locally available adsorbent, has been studied. Experiment was performed on different 8HQ concentration, particle size, and adsorbent dosage. The Langmuir and Freundlich adsorption isotherm model has been tested. The obtained results best fitted the Langmuir model, suggesting monolayer adsorption of 8HQ on POP. The kinetic studies for the adsorption process were also carried out using pseudo-first- and pseudo-second-order models, and the data obtained is best fitted to the pseudo-second-order kinetic model. Thermodynamic parameters were calculated for the adsorption process and the result showed that the values of ΔGads, ΔHads, and ΔSads are −1171.4J/mol, −140J/mol and −40.5 J/K at 303 K. Thus, it can be summarized that the adsorption of 8HQ is spontaneous, chemisorbed, monolayer, and exothermic

Charge transfer complex formation between 8-hydroxyquinoline as the electron donor and citric acid as the electron acceptor has been studied spectrophotometrically in ethanol and methanol solvents at room temperature. Absorption band due to charge transfer complex formation was observed near 320 and 325 nm in ethanol and methanol, respectively. The stoichiometric ratio of the complex has been found 3 : 1 by using Job’s and conductometric titration methods. Benesi-Hildebrand equation has been applied to estimate the formation constant and molecular extinction coefficient. It was found that the value of formation constant was larger in ethanol than in methanol. The physical parameters, ionization potential, and standard free energy change of the formed complex were determined and evaluated in the ethanol and methanol solvents.

The iodine content of water, soil, salt and cereals have been analyzed using Atomic Absorption Spectroscopy (AAS), titrimetry, Fusion and ion selective electrode methods at Geological Survey of Ethiopia, Geosciences Laboratory Center, Addis Ababa, Ethiopia. From the view point of analytical result, the chloride, sodium, potassium, calcium, manganese and magnesium, which are considered as goitrogens are with high concentrations while that of iodine is significantly low (p = 0.055). Likewise, the concentrations of iodine in all the water samples fall in the ranges of the iodine concentration of the various parts of the world, 15µg/l. The iodine concentration in the soil samples taken from non-farm lands (no use of chemical inputs) is significantly higher (p = 0.001) than that of farm lands. Iodine concentration in wheat and barley samples is observed to be significantly low (p = 0.002). This is the major guide to draw the conclusion that community using this water, cereals and salt could face the insufficiencies of iodine in their dietary, which in turn would cause less up-take of iodine by the body resulting iodine deficiency disorder and endemic goiter among the population. Thus, the main approaches to tackle the challenges are the use of iodized salt and oil, fortification of food, water and condiments and distribution of iodine tablets.

This study reports on the adsorption of Hexavalent Chromium from aqueous solutions using activated carbon prepared from bamboo ( Oxytenanthera abyssinica ) waste by KOH activation heating in an electrical furnace at 1073 K for 3 hrs. Batch adsorption experiments were also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage, and temperature of the solution. Kinetic studies of the data showed that the adsorption follows the pseudo-second-order kinetic model. Thermodynamic parameters showed that adsorption on the surface of BWAC was feasible, spontaneous in nature, and exothermic between temperatures of 298 and 318 K. The equilibrium data better fitted the Freundlich isotherm model for studying the adsorption behavior of Hexavalent Chromium by BWAC. IR spectrum for loaded and unloaded BWAC was obtained using FT-IR spectrophotometer. Adsorption efficiency and capacity of Hexavalent Chromium were found to be 98.28% at pH 2 and 59.23 mg/g at 300 K.

It has been studied previously that there exist surface potential in a whole tooth. This work is carried out to investigate the cause of human teeth decay in the oral cavity by electrochemical method. The enamel wafer preferentially allows the passage of monovalent cations and it restricts the passage of monovalent anions so that developing an electric potential. The developed surface potentials were measured between enamel crown’s buccal side and tooth root. Surface potentials examined in all the teeth in the presence of KCl. Then the electric potentials developed this way provide an electric driving force for possible degradation and caries formation of enamel by electric means. This difference is the result of the difference in ionic strength of blood and saliva and types of food intake. It is found that potential increased with increasing KCl concentration and after acid corroded, however the addition of fluoride caused the electric current drop significantly. These results suggest that drop in current indicates a significant increase in the electric resistance of the enamel as a result of fluoride and it is also found that potentials can be affected by the surrounding electrolytes.

This work is carried out to confirm the existence of the surface potentials in extracted tooth by electrochemical method. The surface potentials were measured between enamel crown’s buccal side and tooth root. Surface potentials examined in all the teeth in the presence of KCl. It is found that potential increased with increasing KCl concentration and after acid corroded. The results suggest that potentials can be affected by the surrounding electrolytes and establish an electrical double layer. It is also found that on passing electric current through enamel causes degradation.

Polyaniline (PANI) in its emeraldine salt form was synthesized by chemical method from aniline monomer in the presence of HCl mixed with LiCl and ammonium persulfate as oxidant. Then, a portion of sample was dedoped with NH3 solution and another equal portion was separately postdoped with secondary dopants, such as H2SO4 and HClO4, respectively. Finally, the dried samples of PANI prepared in all its three different forms (emeraldine salt form, undoped emeraldine base, and the two secondary doped forms of PANI) were characterized by UV-visible spectroscopy, cyclic voltammetry (CV) techniques, Fourier transform infrared (FT-IR) spectroscopy, and electrical conductivity measurement. The cyclic voltammograms of PANI in its emeraldine base (PANI-EB) determined the electrochemical behavior and the growth mechanisms of the polymer. The FT-IR and UV-vis spectra confirmed the expected structural modification up on doping, undoping, and postdoping processes of the polymer. Their measured electrical conductivities were from 0.02 for undoped, 156 for primary doped form, and increasing from 158 to 257 S/cm for those secondary doped PANI. The influence of secondary doping on the electrical conductivity was also investigated from their spectroscopic data which shows dramatic rise in conductivity. The result also shows that secondary doping increased the pi conjugation.