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.

Effect of sodium alginate-based superabsorbent hydrogel on tomato growth under different water deficit conditions.

The main challenge facing agriculture today is water scarcity. At present, agriculture consumes around 70 % of the planet's freshwater, much of which is lost through evaporation, leaching and runoff. This wastage, combined with the increased frequency and severity of droughts linked to climate change, is having a considerable negative impact on crops. As a result, the food security of people living in regions with limited water resources is threatened. In this regard, efficient water management using water-saving materials and soil additives such as superabsorbent polymers (SAPs) are recognized as an effective strategy to boost water use efficiency by plants and improve agricultural productivity. The present study fits with this strategy and aims to investigate the effect of new sodium alginate-based hydrogel-treated sandy loam soil on seed emergence and growth of tomatoes as a crop model under different water-deficit stress levels. A set of pot experiments was conducted in a greenhouse chamber using sandy loam soil amended with two levels of hydrogel (0.1 % and 0.5 % by weight) along with untreated control, all under water-deficit stress at three levels: 30 % of the daily amount of required irrigation water (DARW) for different growing cycles (severe stress), 70 % DARW (mild stress), and 100 % DARW (normal irrigation conditions). The germination test showed the absence of phytotoxicity of the developed hydrogel and confirmed its suitability in protecting seedlings from drought stress. Greenhouse experiment results demonstrated that water stress and levels of applied hydrogel significantly (P < 0.05) affected plant growth parameters such as plant height, stem diameter, number of leaves, chlorophyll content, fresh weight, and dry weight compared with the treatments without SAPs. The developed sodium alginate-based SAPs showed relevant agronomical benefits under drought stress by retaining more water and nutrients, thus it had the potential to be used in agriculture for better water management along with significant environmental benefits.

Ultrasound-assisted degradation of organophosphorus pesticide methidathion using CuFe2O4@SiO2-GOCOOH as a magnetic separable sonocatalyst.

Water contamination by pesticides is a critical environmental issue, necessitating the development of sustainable and efficient degradation methods. This study focuses on synthesizing and evaluating a novel heterogeneous sonocatalyst for degrading pesticide methidathion. The catalyst consists of graphene oxide (GO) decorated CuFe2O4@SiO2 nanocomposites. Comprehensive characterization using various techniques confirmed the superior sonocatalytic activity of the CuFe2O4@SiO2-GOCOOH nanocomposite compared to CuFe2O4@SiO2 alone. The enhanced performance is attributed to the combined effects of GO and CuFe2O4@SiO2, including increased surface area, enhanced adsorption capabilities, and efficient electron transfer pathways. Reaction parameters such as time, temperature, concentration, and pH significantly influenced the degradation efficiency of methidathion. Longer reaction times, higher temperatures, and lower initial pesticide concentrations favored faster degradation and higher efficiency. Optimal pH conditions were identified to ensure effective degradation. Remarkably, the catalyst demonstrated excellent recyclability, indicating its potential for practical implementation in pesticide-contaminated wastewater treatment. This research contributes to the development of sustainable methods for environmental remediation, highlighting the promising potential of the graphene oxide decorated CuFe2O4@SiO2 nanocomposite as an effective heterogeneous sonocatalyst for pesticide degradation.