Effectiveness of a biogenic composite derived from cattle horn core/iron nanoparticles via wet chemical impregnation for cadmium (II) removal in aqueous solution.

The objective of the current study was focused on the potential adsorption capability of a biogenic hydroxyapatite/iron nanoparticles-based composite tailored for the elimination of toxic pollutant, Cd(II) ions. Morphological along with physicochemical properties of composites were analyzed by different techniques including Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). It has been noticed an increase in cell parameters of prepared composites with an increase in the amount of nanoparticles. The best adsorbent was found to be the one with a 5% amount of nanoparticles (P400Fe(5%)). The kinetics studies have shown that the pseudo-first-order-models were in good agreement for the removal of Cd(II) ions onto P400Fe(5%) at any concentration, suggesting a physisorption mechanism. Besides, isotherms analysis has consistently revealed Freundlich as the model better explained the isotherm data, with a maximum removal capacity of 392.3 mg g-1, higher compared to many adsorbents. Thermodynamically, the removal adsorption process of Cd(II) ions onto the composite favorable, exothermic, and spontaneous. The regeneration study has been also investigated with reusability used until four cycles. The overall results pointed out the suitability and efficiency of the prepared biogenic composite for the elimination of metal pollutants in wastewater.

Surface modification of biomaterials based on cocoa shell with improved nitrate and Cr(vi) removal.

The present work addresses the development of simple, low-cost and eco-friendly cocoa-shell-based materials for efficient removal of heavy metal hexavalent chromium (Cr(vi)), and toxic nitrate (NO3 -) from aqueous solution. A conventional treatment process was used to purify cocoa shell (CS) into an adsorbent, followed by chemical grafting of dendrimers to promote its surface properties for nitrate and Cr(vi) removal. The morphology, surface charge, structure and stability of the new adsorbent were investigated by scanning electron microscopy, Fourier transform infrared and UV-visible spectroscopies, zeta potential, X-ray photoelectron spectrometry, and differential scanning calorimetry. The successful chemical grafting of the dendrimer (polyethyleneimine, PEI) onto purified CS was confirmed. CS-T-PEI-P proved to be a very efficient candidate for the removal of nitrate and chromium(vi). Removal of the two pollutants at different initial concentrations and pH values was studied and discussed. Sorption of chromium and nitrate was found to obey 2nd-order kinetics and a Freundlich-type isotherm, affording an uptake adsorption of 16.92 mg g-1 for NO3 - and 24.78 mg g-1 for Cr(vi). These results open promising prospects for its potential applications as a low cost catalyst in wastewater treatment.

Comparison of HCl and H2SO4 for the acid activation of a cameroonian smectite soil clay: palm oil discolouration and landfill leachate treatment.

Vertisols occupy approximately 1,200,000 ha in Northern Cameroon. Their richness in smectites allows for the production of "bleaching earths" necessary for refining palm oil, and their effluent is used for leachate treatment. In the present work, two mineral acids (HCl and H2SO4) were compared, and the most efficient acid with the lowest cost was determined for use in industrial applications. Under similar experimental conditions (ratio of acid solution/clay mass = 5/1, temperature = 97 °C, stirring time = 4 h), the quantity of cations (Fe2+, Fe3+, Al3+) solubilised during acid activation, palm oil discolouration rate by each activated sample and the financial cost of 5 L of acid solution that is required for the acid activation of one kilogram of smectite clay were compared. It was found that 2N H2SO4 was more efficient than 1N HCl and 1N H2SO4, considering palm oil bleaching efficiency and cost. The filtrate collected after the acid activation of vertisols was rich in H+ (2.04.10-1M), Fe2+ (2.8.10-3M), Fe3+ (4.2.10-2M) and Al3+ (9.2.10-2M) ions. One gram of smectite clay material produced 9 mL of this filtrate that was used for the treatment of leachate from a controlled landfill. The leachate colour decreased from 4262 to 285 PtCo units, while the corresponding chemical oxygen demand (COD) decreased from 802 to 128 mg/L. Thus, the most effective acid for industrial bleaching earth production from vertisol is 2N H2SO4 acid.