Effect of Physical and Chemical Activation on the Removal of Hexavalent Chromium Ions Using Palm Tree Branches

Nowadays the removal of heavy metals from wastewater is essential due to their high toxicity and impact on human health. In the present study, branches of palm trees were converted into activated carbon by chemical and physical activation. The prepared samples were used for the removal of Cr(VI) from their aqueous solution. Chemical activation was carried out using (20 and 50%) H3PO4 and K2CO3, and physical activation was performed using steam. Batch adsorption experiments were carried out to examine the removal process under factors such as pH and pHpzc. The metal ion removal was pH dependent and reached maximum removal at pH 2. Experimental data were analyzed using Langmuir, Freundlich, and Flory-Huggins isotherms. The adsorption studies revealed that the removal of Cr(VI) ions was well fitted with Langmuir isotherm. The adsorption kinetics well fitted using a pseudo second-order kinetic model. Column studies revealed that the highest bed volume (60 BV) was observed for the sample activated with 50% H3PO4. The adsorption efficiency was enhanced with acid treatment (50% H3PO4) and reduced by steam.

Photosynthetic Active Pigments Changes in Norway Spruce (Picea abies) under the Different Acclimation Irradiation and Elevated CO2 Content

Photosynthetic active pigments content (chlorophylls and carotenoids) in Norway spruce (Picea abies) needles was measured by absorption spectroscopy. Norway spruce was exposed to low and high photosynthetic active radiation and ambient and elevated CO2 concentration. It was investigated that combination of low photosynthetic active radiation and elevated concentration of CO2 resulted in stimulation of chlorophylls and carotenoids production. Combination of high photosynthetic active radiation and elevated CO2 concentration led to overall chlorophylls and carotenoids content decrease. Moreover, specific leaf area trend could be used as a potentially reliable indicator of plant stress response.

Adsorption of Hexavalent Chromium from Aqueous Solution Using Chemically Activated Carbon Prepared from Locally Available Waste of Bamboo (Oxytenanthera abyssinica)

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.

Gas Chromatography Mass Spectrometry Identification of Labile Radicals Formed during Pyrolysis of Catechool, Hydroquinone, and Phenol through Neutral Pyrolysis Product Mass Analysis

Catechol, hydroquinone, and phenol are known to be environmental pollutants due to their ability to generate environmentally free radicals, which cause millions of deaths worldwide. Recently, efforts have been done to precisely identify the origin and the nature of those free radicals employing EPR-LTMI technique. All the three precursors generate cyclopentadienyl radical as major pyrolysis products and phenoxyl radical as both pyrolysis and photolysis products which were obtained from phenol; ortho-semiquinone and para-semiquinone were seen, respectively, from the pyrolysis of catechol and hydroquinone. However, it has been suspected that the solely use of the EPR-LTMI did not allow the isolation of the more labile radicals that is supposedly terminated by radical-radical or radical-surface interaction. The present study reports the gas chromatography mass analysis of the pyrolysis products from catechol, hydroquinone, and phenol. Naphthalene , indene, and hydroxyindene were observed as the pyrolysis products of hydroquinone, while fluorene, 1H-indenol and its isomer 1H-inden-1-one 2,3 dihydro, acenaphthylene, benzofuran-7-methyl, and benzofuran-2-methyl were observed as pyrolysis products of catechol. Dibenzo dioxin and dibenzo furan were observed from pyrolysis of catechol and hydroquinone. Those products result from the combination of radicals such as cyclopentadienyl, para-semiquinone, ortho-semiquinone, hydroxyl-cyclohexadienyl, phenoxyl, and most importantly Hydroxycyclopentadienyl which was not identified by EPR-LTMI.

Hydrocarbons Migration through Groundwater Convergence toward Saline Depressions: A Case Study, Sidi El Hani Discharge Playa, Tunisian Sahel

This paper aims to provide proofs of hydrocarbons migration from petroleum reservoirs towards the surface of discharge playas. This is a case study of the discharge playa of Sidi El Hani, eastern Tunisia. The geochemistry of water of some hydrological drills in the Sahel area and of water from the discharge playa proves relatedness between the deep aquifer and the water of the discharge playa. Thus, the hydrology is now more than likely converging from the subsurface. This convergence may be an agent of transport of hydrocarbons. Concerning the organic matter within the discharge playa, high percentages of different fractions seem abnormal in such a saline context. This maturated organic matter should be viewed in the widest context of a multidisciplinary study taking into account the presence of petroleum potentials in the subsurface, the converging hydrogeology, and the tectonised region. The high percentage of Aromatic Polycyclic Hydrocarbon (APH) may be the result of hydrocarbons migration rather than anthropogenic pollution. As for the reinterpretation of previous works about the organic matter in playas done in sebkha Moknine, the contaminated organic matter, which was interpreted as a human induced activity, may have another origin from a reservoir located in the subsurface of the Sahel area.

Removal of Methyl Violet 2B from Aqueous Solution Using Casuarina equisetifolia Needle

One of the major contaminants of water bodies is dye pollutants that come from textile, paper, and leather industries. In this study, Casuarina equisetifolia needle (CEN) is used to remove methyl violet 2B (MV) from aqueous solutions. Batch experiments were done to investigate the contact time, effect of pH, initial dye concentrations, and temperature. Langmuir and Freundlich isotherm models were used to describe the interaction between the adsorbate and adsorbent. The sorption mechanism was described using Lagergren 1st order, pseudo 2nd order, and Weber-Morris intraparticle diffusion models. FTIR spectroscopy was used to analyze the functional groups of CEN before and after sorption with MV. Optimal conditions were found to be at room temperature with 2 h contact time and no pH adjustment was needed. Experimental data was best fitted onto Langmuir model with maximum adsorption capacity of 164.99 mg/g, while pseudo 2nd order best described the experimental data for the kinetics study. Thermodynamic parameters such as change in Gibbs free energy (), enthalpy (), and entropy () were also investigated.

Assessment of Heavy Metals Concentration in Arsenic Contaminated Groundwater of the Chaco Plain, Argentina

The occurrence and distribution of arsenic and 23 other trace elements have been investigated in groundwater from Comandante Fernández Department in the Central region of Chaco Province, Northern Argentine. The arsenic concentrations samples ranged between 0.7 to 1990 µg L−1; 91% (n=45) exceeds the 10 µg L−1 World Health Organization (WHO) provisional standard limits for drinking water. Fluorine was detected in 31% of groundwater samples. Furthermore, there was found a significant correlation between As and F (r2=0.50), indicating an association in the prevalence of both elements. In addition, about 78%, 31%, 16%, 13%, and 4.5% of groundwater samples had, respectively, B, Fe, Al, Mn, and Sb exceeding Código Alimentario Argentino (CAA) guideline values. In contrast of the previously values descript, the corresponding to Cr, Be, Ni, Pb, Ag, Se, and Zn were found below the quantification limit. The presence of As and trace elements in groundwater represents an important issue because it can cause a public health problem.

Evaluation of Preoxidized SUS304 as a Catalyst for Hydrocarbon Reforming

The feasibility of oxidation pretreated SUS304 alloy tube as a hydrocarbon reforming catalyst was investigated. It was hypothesized that preoxidation resulted in the dispersion of the active component and the formation of mixed metal oxides on the surface of the alloy which consequently rendered the alloy tube catalytically active towards reforming reaction. Oxidation pretreatment was done in O2 at 1000°C for 2 hours followed by a catalytic evaluation at 730°C for 2 hours. Tetradecane was used as a model compound for steam, partial oxidation, and CO2 reforming experiments. According to the collected XRD pattern, α-Fe2O3 and Cr2O3 were formed after oxidation pretreatment. In addition, SEM-EDX analysis showed a very rough surface composed of oxygen, chromium, iron, and nickel. Catalytic evaluation of the sample displayed activity towards partial oxidation and CO2 reforming which led to the conclusion that oxidation pretreated SUS304 alloy tube has a potential as a catalyst for partial oxidation and CO2 reforming of hydrocarbons. However, the varying activity observed suggested that each reforming reaction requires a specific formulation and morphology.

Batch Adsorption of Maxilon Red GRL from Aqueous Solution by Natural Sugarcane Stalks Powder

Sugarcane stalks powder was tested for its efficiency of removing a textile dye Maxilon Red GRL from aqueous solution. Different parameters affecting dye removal efficiency were studied. These parameters include contact time, initial dye concentration, adsorbent dose, ionic strength, pH, and temperature. Langmuir and Freundlich isotherm models were applied to the equilibrium data. The data fitted well with the Langmuir isotherm (). The maximum monolayer adsorption capacity () was found to be 20.96 mg/g at an initial pH of 7.2. The temperature variation study showed that dye adsorption is exothermic and spontaneous with increased randomness at the solid solution interface. The results indicated that sugarcane stalks could be an alternative for more costly adsorbents used for dye removal. The kinetic of the adsorption process followed the pseudo second-order kinetics model.

Closed Anaerobic Biotransformation Products of Organoarsenic Compounds in Fucus distichus

The closed anaerobic decomposition extracts of Fucus distichus incubated with seawater and sediment, and without sediment as control, were subjected to extractions and isolation on Sephadex LH 20 and Cellulose Thin Layer Chromatography. The decomposition extracts and isolates were analyzed by using both the Hydride Generation Gas Chromatography Atomic Absorption Spectrometry (HG-GC-AAS) and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICPMS) to identify the arsenic species in the equilibrium mixtures of the seaweed and filtrates separately. In the methanol seaweed extract, equilibrium mixture of arsenosugars (AS) AS1 and AS2 and their biotransformation products of dimethylarsinoylethanol (DMAE) and dimethylarsinic acid (DMAA) were identified. In the methanol filtrate extract of the mixture, only DMAE and DMAA were identified. However, in the control methanol filtrate extract five organoarsenic species, AS1 and AS2, one unidentified hidden organoarsenic species, DMAE and DMAA were identified in the equilibrium mixture. This result confirmed that the hidden organoarsenic species in Fucus distichus, AS1 and AS2, and an unidentified organoarsenic compounds are biotransformed to only DMAE and DMAA under an anaerobic condition. This also suggests that DMAE and DMAA are strong intermediate candidates for the generation of arsenobetaine, from arsenoribosides in the marine food webs.