Fixed-bed adsorption of Pb(ii) and Cu(ii) from multi-metal aqueous systems onto cellulose-g-hydroxyapatite granules: optimization using response surface methodology.

We prepared cellulose microfibrils-g-hydroxyapatite (CMFs-g-HAPN (8%)) in a granular form. We evaluated the ability of these granules to eliminate Pb(ii) and Cu(ii) ions from aqueous solution in dynamic mode using a fixed-bed adsorption column. Several operating parameters (inlet ion concentration, feed flow rate, bed height) were optimized using response surface methodology (RSM) based on a Doehlert design. Based on ANOVA and regression analyses, adsorption was found to follow the quadratic polynomial model with p < 0.005, R2 = 0.976, and R2 = 0.990, respectively, for Pb(ii) and Cu(ii) ions. Moreover, three kinetic models (Adams-Bohart, Thomas, Yoon-Nelson) were applied to fit our experimental data. The Thomas model and Yoon-Nelson model represented appropriately the whole breakthrough curves. The Adams-Bohart model was suitable only for fitting the initial part of the same curves. Our adsorbent exhibited high selectivity towards Pb(ii) over Cu(ii) ions in the binary metal system, with a maximum predicted adsorption capacity of 59.59 ± 3.37 and 35.66 ± 1.34 mg g-1, respectively. Under optimal conditions, multi-cycle sorption-desorption experiments indicated that the prepared adsorbent could be regenerated and reused up to four successive cycles. The prepared CMFs-g-HAPN was an efficient and effective reusable adsorbent for removal of heavy metals from aqueous systems, and could be a suitable candidate for wastewater treatment on a large scale.

Efficient removal of Cu2+ and methylene blue pollutants from an aqueous solution by applying a new hybrid adsorbent based on alginate-chitosan and HAP derived from Moroccan rock phosphate.

Alginate-chitosan/hydroxyapatite (Alg-Cs/HAP) beads were prepared as adsorbent to remove methylene blue (MB) and copper ions from an aqueous solution using a batch system. FTIR, TGA, point of zero charge (pHpzc), SEM, XRD, and BET analysis were used to characterize the elaborated material. The effect of several parameters such as initial pH value, adsorbent dose, temperature, contact time, and initial pollutant concentration were also investigated. The obtained results showed that Alg-Cs/HAP exhibit excellent adsorption properties for Cu (II) and MB removal, with high adsorption capacities of copper ions (208.34 mg/g) and methylene blue (454.54 mg/g). The kinetic of the adsorption process is correlated with the pseudo-first-order for methylene blue and the pseudo-second-order for copper ions. The equilibrium data for MB dye fitted the Freundlich isotherm model, thus implying that the adsorption process consists of multilayer adsorption as well as interactions between the adsorbate and the adsorbent. The equilibrium data for copper ions corresponds closely with the Langmuir model which suggests that the adsorbed molecules occur over a monolayer. Various thermodynamic parameters such as the standard Gibbs energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were calculated. All results indicated that Alg-Cs/HAP material has a good potential for the treatment of wastewater.

Design and development of a highly efficient reusable zeolite impregnated ZnAl2O4 catalyst for biodiesel production.

As the demand for sustainable energy sources expands, the production of biodiesel has attracted great attention. The development of effective and ecologically friendly biodiesel catalysts has become an urgent need. In this context, the goal of this study is to develop a composite solid catalyst with enhanced efficiency, reusability, and reduced environmental impact. For that, eco-friendly, and reusable composite solid catalysts have been designed by impregnating different amounts of zinc aluminate into a zeolite matrix (ZnAl2O4@Zeolite). Structural and morphological characterizations confirmed the successful impregnation of zinc aluminate into the zeolite porous structure. Catalytic experiments revealed that the catalyst containing 15 wt% ZnAl2O4 showed the highest conversion activity of fatty acid methyl esters (FAME) of 99% under optimized reaction conditions, including 8 wt% catalyst, a molar ratio of 10:1 methanol to oil, a temperature of 100 °C, and 3 h of reaction time. The developed catalyst demonstrated high thermal and chemical stability, maintaining good catalytic activity even after five cycles. Furthermore, the produced biodiesel quality assessment has demonstrated good properties in compliance with the criteria of the American Society for Testing and Materials ASTM-D6751 and the European Standard EN14214. Overall, the findings of this study could have a significant impact on the commercial production of biodiesel by offering an efficient and environmentally friendly reusable catalyst, ultimately reducing the cost of biodiesel production.

A Novel Approach to Prepare Cellulose-g-Hydroxyapatite Originated from Natural Sources as an Efficient Adsorbent for Heavy Metals: Batch Adsorption Optimization via Response Surface Methodology.

In the present research, we describe a novel approach for in situ synthesis of cellulose microfibrils-grafted-hydroxyapatite (CMFs-g-HAPN (8%)) as an adsorbent using phosphate rock and date palm petiole wood as alternative and natural Moroccan resources. The synthesized CMFs-g-HAPN (8%) was extensively characterized by several instrumental techniques like thermogravimetry analysis, Fourier transform infrared spectroscopy, X-ray diffraction, 31P nuclear magnetic resonance, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The developed adsorbent was used to remove Pb(II) and Cu(II) from aqueous solutions. The influences of different adsorption parameters such as contact time, initial metal concentration, and amount of adsorbent were also investigated thoroughly using response surface methodology in order to optimize the batch adsorption process. The results confirmed that the adsorption process follows a polynomial quadratic model as high regression parameters were obtained (R 2 value = 99.8% for Pb(II) and R 2 value = 92.6% for Cu(II)). According to kinetics and isotherm modeling, the adsorption process of both studied ions onto CMFs-g-HAPN (8%) followed the pseudo-second-order model, and the equilibrium data at 25 °C were better fitted by the Langmuir model. The maximum adsorption capacities of the CMFs-g-HAPN (8%) adsorbent toward Pb(II) and Cu(II) are 143.80 and 83.05 mg/g, respectively. Moreover, the experiments of multicycle adsorption/desorption indicated that the CMFs-g-HAPN (8%) adsorbent could be regenerated and reused up to three cycles. The high adsorption capacities of both studied metals and regeneration performances of the CMFs-g-HAPN (8%) suggest its applicability as a competitive adsorbent for large-scale utilization.