Dual-functionalized strontium phosphate hybrid nanopowder for effective removal of Pb 2+ and malachite green from aqueous solution

Optimization Conditions of Malachite Green Adsorption onto Almond Shell Carbon Waste Using Process Design

Almond shell-based biocarbon is a cheap adsorbent for the removal of malachite green, which has been investigated in this work. FT-IR, DRX, and BET were used to characterize almond shell-based biocarbon. The nitrogen adsorption-desorption isotherms analysis results showed a surface area of 120.21 m2/g and a type H4 adsorption isotherm. The parameters of initial dye concentration (5-600 mg.L-1), adsorbent mass (0.1-0.6 mg), and temperature (298-373 K) of adsorption were investigated. The experiments showed that the almond shell could be used in a wide concentration and temperature range. The adsorption study was fitted to the Langmuir isotherm and the pseudo-second-order kinetic model. The results of the FT-IR analysis demonstrated strong agreement with the pseudo-second-order chemisorption process description. The maximum adsorption capacity was calculated from the Langmuir isotherm and evaluated to be 166.66 mg.g-1. The positive ∆H (12.19 J.mol-1) indicates that the adsorption process is endothermic. Almond shell was found to be a stable adsorbent. Three different statistical design sets of experiments were taken out to determine the best conditions for the batch adsorption process. The optimal conditions for MG uptake were found to be adsorbent mass (m = 0.1 g), initial dye concentration (C0 = 600 mg.L-1), and temperature (T = 25 °C). The analysis using the D-optimal design showed that the model obtained was important and significant, with an R2 of 0.998.

Hexabromocyclododecane alters malachite green and lead(II) adsorption behaviors onto polystyrene microplastics: Interaction mechanism and competitive effect

The role of microplastics (MPs) as a carrier of pollutants in water environment is an emerging issue; however, information regarding the underlying mechanisms for malachite green (MG) and Pb(II) adsorption onto hexabromocyclododecane (HBCD)-polystyrene (PS) composites MPs (HBCD-PS MPs) is still lacking. In this study, the adsorption behaviors and mechanisms of MG and Pb(II) onto PS and HBCD-PS MPs were investigated in batch adsorption experiments. The amounts of MG and Pb(II) adsorbed onto PS MPs were negligible while the presence of HBCD significantly enhanced the adsorption of MG and Pb(II) onto HBCD-PS MPs. The results of intra-particle and film diffusion model confirmed that the adsorption of MG and Pb(II) onto HBCD-PS MPs was dominated by intra-particle diffusion. The maximum adsorption amount (q_m) of Pb(II) and MG onto HBCD-PS MPs followed the sequence of Pb(II) (3.33 μmol g^-1) > MG (1.87 μmol g^-1). In binary systems, MG and Pb(II) showed competitive adsorption onto HBCD-PS MPs, and Pb(II) exhibited relatively higher affinity to be adsorbed onto HBCD-PS MPs. Solution pH and salinity played a crucial role in the adsorption process. XPS analysis suggested that the -Br participated in the adsorption process as an electron-withdrawing group. Overall, electrostatic interaction regulated the adsorption of MG and Pb(II) onto HBCD-PS MPs. Results from this study demonstrated that HBCD could enhance the role of MPs in the MG and Pb(II) migration by changing their adsorption behavior onto MPs.

Development of magnetic porous coordination polymer adsorbent for the removal and preconcentration of Pb(II) from environmental water samples

A novel porous coordination polymer adsorbent (BTCA-P-Cu-CP) based on a piperazine(P) as a ligand and 1,2,4,5-benzenetetracarboxylic acid (BTCA) as a linker was synthesized and magnetized to form magnetic porous coordination polymer (BTCA-P-Cu-MCP). Fourier transform infrared (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscope(FESEM), energy-dispersive X-ray spectroscopy(EDS), CHN, and Brunauer-Emmett-Teller(BET) analysis were used to characterize the synthesized adsorbent. BTCA-P-Cu-MCP was used for removal and preconcentration of Pb(II) ions from environmental water samples prior to flame atomic absorption spectrometry(FAAS) analysis. The maximum adsorption capacity of BTCA-P-Cu-MCP was 582 mg g^-1. Adsorption isotherm, kinetic, and thermodynamic parameters were investigated for Pb(II) ions adsorption. Magnetic solid phase extraction (MSPE) method was used for preconcentration of Pb(II) ions and the parameters influencing the preconcentration process have been examined. The linearity range of proposed method was 0.1-100 μg L^-1 with a preconcentration factor of 100. The limits of detection and limits of quantification for lead were 0.03 μg L^-1 and 0.11 μg L^-1, respectively. The intra-day (n = 7) and inter-day (n = 3) relative standard deviations (RSDs) were 1.54 and 3.43% respectively. The recoveries from 94.75 ± 4 to 100.93 ± 1.9% were obtained for rapid extraction of trace levels of Pb(II) ions in different water samples. The results showed that the BTCA-P-Cu-MCP was steady and effective adsorbent for the decontamination and preconcentration of lead ions from the aqueous environment.

Successive removal of Pb2+ and Congo red by magnetic phosphate nanocomposites from aqueous solution

The successive removal of Pb²⁺ and Congo red (CR) from aqueous solution by three magnetic phosphate nanocomposites (Fe₃O₄@Sr₅(PO₄)₃(OH), Fe₃O₄@Ba₃(PO₄)₂, and Fe₃O₄@Sr_5xBa_3x(PO₄)₃(OH), denominated FSP, FBP, and FSBP, respectively) was systematically investigated in comparison with Fe₃O₄ (denominated F) nanoparticle. FSP, FSBP, F, and FBP exhibited a high removal capacity of 351, 272, 76, and 23 mg/g for Pb²⁺, respectively. These materials could be reclaimed by magnetic separation and then used for successive CR remediation, showing a high CR removal capacity of 224, 163, 126, and 61 mg/g, respectively. The isothermal and kinetic behavior fitted well with the Langmuir model and pseudo-second-order model, respectively. The successive removal mechanism by these magnetic phosphates was proposed to be the ion exchange between Pb²⁺ and Sr²⁺ in the lattice and then the loaded Pb²⁺ could contact with anionic dye CR to form precipitation on the surface of materials, inhibiting the leaching of Pb²⁺ ions from the reclaimed materials back into water. In addition, these materials showed good reusability and practical application. This study demonstrated the potential of these low cost phosphate nanocomposites as promising materials for successive removal of Pb²⁺ and CR from water.