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• Co-pyrolysis biochars have higher Pb removal capacities than original biochar. • Metaphosphate within co-pyrolysis biochar promoted Pb sorption. • Carbon stability of co-pyrolysis biochars is enhanced compared with original biochar. When used separately, biochar and orthophosphate are good materials to remove Pb from water, but few studies have been done on Pb removal by biochar-orthophosphate composite. Here biochar-orthophosphate composites were prepared by co-pyrolyzing rape straw with orthophosphate (Ca(H 2 PO 4) 2 ·H 2 O / KH 2 PO 4) at ratio of 5:1 (W:W), noted as WBC-Ca and WBC-K, respectively, so as to explore the Pb removal capacities and mechanisms of co-pyrolysis biochars. The sorption isotherms of Pb were well fitted with Langmuir model and the maximum sorption capacities of Pb by original biochar, WBC-Ca, and WBC-K were 184.1, 566.3 and 1559 mmol kg−1, respectively. The results of FTIR, XRD, and XPS analyses showed that phosphorus in biochar played an important role to remove Pb by forming lead-precipitates. However, the species of lead-precipitates in three types of Pb-loaded biochars were Pb 5 (PO 4) 3 Cl, Pb 2 P 2 O 7 , and Pb n/2 (PO 3) n , individually, and that was because speciation of phosphorus had undergone significant thermochemical transformation during pyrolysis process. Orthophosphate in WBC-Ca was mainly transformed to pyrophosphate, while orthophosphate in WBC-K was transformed to both metaphosphate and pyrophosphate. The present results warrant the promising application of co-pyrolysis biochar derived from rape straw and orthophosphate in removal of Pb from wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Smart aminosilane modified- SnO 2 /Porous silica nanocomposite was synthesized. • High efficiency removal of lead ions and bacterial inactivation were obtained. • The maximum adsorption capacity was 653.62 mg g−1. • Nanocomposite possessed exceptional disinfection ability toward E-Coli and S. aureus bacteria. Abstract The aim of the present study is to synthesize a new and proficient nanoadsorbent for rapid removal of heavy metals and disinfection of microorganisms. The proposed nanoadsorbent was fabricated using SnO 2 nanoparticles as the core, coated with mesoporous silica and further modified with 3-Aminopropyl triethoxysilane to render SnO 2 /PSi/NH 2 nanocomposite. The nanocomposite was characterized using Fourier Transform Infrared (FTIR), X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Nitrogen adsorption-desorption analysis. The potential of the resultant SnO 2 /PSi/NH 2 nanocomposite for the convenient removal of Lead ions in a batch systems was investigated as a function of solution pH, contact time, adsorbent dosage, temperature and metal ion concentration. The adsorption behavior was in good agreement with Sips and Langmuir isotherm models. The maximum adsorption capacity of SnO 2 /PSi/NH 2 was 653.62 mg g−1. Furthermore, the desorption experiments demonstrated that the proposed nanocomposite could be used frequently for at least three consecutive cycles with minor losses in adsorption performance. The bacterial inactivation ability of SnO 2 /PSi/NH 2 toward E-Coli and S. aureus bacteria was also evaluated using disk diffusion and linear cultivation tests, according to which the SnO 2 /PSi/NH 2 nanocomposite possessed exceptional disinfection ability toward both bacteria, specifically S. aureus. [ABSTRACT FROM AUTHOR]

Four new types of carboxylate-ferroxane nanoparticles, namely; maleate ferroxane (MF), fumarateferroxane (FF), para -amino benzoate ferroxane (PABF) and para -hydroxy benzoate ferroxane (PHBF) were synthesized, characterized and used for lead removal from aqueous solutions. Lepidocrocite nanoparticles were also synthesized and characterized asa precursorforcarboxylate-ferroxanes. FTIR, SEM and DLS analysis characterized the synthesized samplesand final Pb(II) concentration were analysed using inductively coupled plasma atomic emission spectrometer. Performance evaluation of the nanoparticlesin adsorption process was achieved using Taguchi experimental design. Variables in adsorption process were initial pH, contact time, adsorbent dose, adsorbent typeand initial concentration of Pb 2+ ions. The initial Pb(II) concentration was the most influential factor in the adsorption process among the five factors. Adsorption of lead was performed through two possible mechanisms; ion exchange and complex formation. Maleate ferroxane performed the best lead removal efficiency among the four types of ferroxane nanostructures studied. The adsorption kinetic data described well with a pseudo-second-order model and the equilibrium data fitted well to the Frendlich isotherm. [ABSTRACT FROM AUTHOR]

Abstract: The present study was aimed at examining the ability of a natural zeolitic volcanic tuff to remove Pb(II) ions from aqueous solutions under various conditions. The effects of various parameters such as optimum adsorbent mass, contact time, pH of the medium, Pb(II) concentration, and temperature were investigated. In addition, different adsorption isotherms were obtained using concentrations of Pb(II) ions ranging from 1mg/L to 200mg/L. The adsorption process follows second-order reaction kinetics and follows the Langmuir adsorption isotherm. The thermodynamic parameters are discussed in this article, including changes in Gibbs free energy, entropy, and enthalpy, for the adsorption of Pb(II) on tuff, and it is revealed that the adsorption process was spontaneous and exothermic under natural conditions. The maximum removal efficiency of 92% was obtained at a pH of 5 with a 25-min contact time for a 10g/L solid-to-liquid ratio and an initial heavy metal concentration of 100mg/L. [Copyright &y& Elsevier]

Abstract: Recycling treatment of cable insulation resin generated from electric wires and cables was investigated. Conventional insulation PVC contains a lead component, tribase, as a thermal stabilizer and lead removal is necessary to recycle this PVC as insulation resin. This paper describes a solid surface adsorption method using ion exchange resin to remove the fine lead containing particles from PVC dissolved solution. Low lead concentration in the recovered PVC, complying with the requirements of RoHS, was achieved. [Copyright &y& Elsevier]

The capacity of sepiolite for the removal of lead ions from aqueous solution was investigated under different experimental conditions. The Langmuir and Freundlich equations, which are in common use for describing sorption equilibrium for wastewater-treatment applications, were applied to data. The constants and correlation coefficients of these isotherm models for the present system at different conditions such as pH, temperature and particle size were calculated and compared. The equilibrium process was well described by the Langmuir isotherm model and the maximum sorption capacity was found to be 93.4 mg/g for the optimal experimental condition. The thermodynamic parameters (ΔG°, ΔH° and ΔS°) for lead sorption on the sepiolite were also determined from the temperature dependence. The influences of specific parameters such as the agitation speed, particle size and initial concentration for the kinetic studies were also examined. The sorption kinetics were tested for first order reversible, pseudo-first order and pseudo-second order reaction and the rate constants of kinetic models were calculated. The best correlation coefficients were obtained using the pseudo-second order kinetic model, indicating that lead uptake process followed the pseudo-second order rate expression. [Copyright &y& Elsevier]

• A novel surface mole-ratio (SMR) method was established and applied for delineating Pb-P precipitation and Pb adsorption. • The P-Pb-AAF system was applied for delineating Pb-P precipitation and Pb adsorption for elaborating the SMR method. • The SMR can be expanded in binary adsorbates and multi-adsorbate solutions, such as natural water, wastewater and soils. The enhancement effects of phosphate (P) on Pb removal by adsorbents have been attributed to co-adsorption of P and Pb, the formation of P-Pb surface ternary surface complexes, and surface precipitation of P and Pb. However, distinguishing adsorption from surface precipitation in multi-adsorbate systems has been a challenge. For the first time, a surface mole-ratio (SMR) method was established and applied for delineating Pb-P precipitation and Pb adsorption on an acrylic amine fiber (AAF) adsorbent. In elaborating the SMR method, we developed Pb removal experiments by mixing solutions containing 0.2 g/L of AAF, 6 and 12 μmol/L P, and 0–35 μmol/L Pb. When the removed Pb/P (μmol/μmol) was plotted as a function of the equilibrium Pb (μmol/L), the SMR diagram exhibited a turning-point similar to the Pb/P mole ratio of 5/3 = 1.67 in pyromorphite (Pb 5 (PO 4) 3 OH) precipitate. The SMR diagram indicated that when the Pb concentration increased, the precipitate formed first; after all P formed precipitates, Pb was removed by adsorption. The precipitation and adsorption processes were further confirmed by other SMR diagrams, FTIR, SEM-EDX, and XRD analysis. The SMR method will have broad applications in determining the removal mechanisms of multi-adsorbates by adsorbents and coagulants, and stabilization mechanisms of heavy metals in soils. With the development and application of more modern in-situ characterization techniques, SMR method will be more effective. [ABSTRACT FROM AUTHOR]