Magnetic Biochar Derived from Fenton Sludge/CMC for High-Efficiency Removal of Pb(II): Synthesis, Application, and Mechanism

Magnetic biochar composites (MBC) were developed by a simple one-step pyrolysis method using Fenton sludge waste solid and carboxymethyl cellulose sodium. Detailed morphological, chemical, and magnetic characterizations corroborate the successful fabrication of MBC. Batch adsorption experiments show that the synthesized MBC owns high-efficiency removal of Pb(II), accompanied by ease-of-separation from aqueous solution using magnetic field. The experiment shows that the equilibrium adsorption capacity of MBC for Pb(II) can reach 199.9 mg g^-1, corresponding to a removal rate of 99.9%, and the maximum adsorption capacity (q_m) reaches 570.7 mg g^-1, which is significantly better than that of the recently reported magnetic similar materials. The adsorption of Pb(II) by MBC complies with the pseudo second-order equation and Langmuir isotherm model, and the adsorption is a spontaneous, endothermic chemical process. Investigations on the adsorption mechanism show that the combination of Pb(II) with the oxygen-containing functional groups (carboxyl, hydroxyl, etc.) on biochar with a higher specific surface area are the decisive factors. The merits of reusing solid waste resource, namely excellent selectivity, easy separation, and simple preparation make the MBC a promising candidate of Pb(II) purifier.

Magnetic supramolecular polymer: Ultrahigh and highly selective Pb(II) capture from aqueous solution and battery wastewater

For the practical capture of heavy metal ions from wastewater, fabricating environmental friendly adsorbents with high stability and super adsorption capacity are pursuing issue. In this work, we develop magnetic supramolecular polymer composites (M-SMP) by using a simple two-step hydrothermal method. Systematical characterizations of morphological, chemical and magnetic properties were conducted to confirm the formation of M-SMP composites. The resulting M-SMP composites were applied to remove Pb(II) from aqueous solution and from real battery wastewater, and easy separation was achieved using a permanent magnet. By investigating the effects of various parameters, we optimized their operating condition for Pb(II) adsorption by the M-SMP. The uptake of Pb(II) onto M-SMP fitted well the pseudo-second-order and Langmuir isotherm models, and favourable thermodynamics showed a spontaneous endothermic process. The SMP endowed M-SMP with ultrahigh adsorption capacity for Pb(II) (946.9 mg g^-1 at pH = 4.0, T = 298 K), remarkable selectivity, satisfactory stability and desirable recyclability. In Pb-contaminated lead-acid battery industrial wastewater, the concentration of Pb(II) declined from 18.070 mg L^-1 to 0.091 mg L^-1, which meets the current emission standard for the battery industry. These merits, combined with simple synthesis and convenient separation, make M-SMP an outstanding scavenger for the elimination of industrial Pb(II) wastewater.

Highly-dispersed ruthenium precursors via a self-assembly-assisted synthesis of uniform ruthenium nanoparticles for superior hydrogen evolution reaction

For the first time, highly-dispersed ruthenium precursors via a hydrogen-bond-driven melamine–cyanuric acid supramolecular complex (denoted CAM) self-assembly-assisted synthesis of uniform ruthenium nanoparticles with superior HER performance under both acidic and alkaline conditions are reported. Electrochemical tests reveal that when the current density is −10 mA cm⁻², the optimal Ru/CNO electrocatalyst could express low overpotentials of −18 mV and −46 mV, low Tafel slopes of 46 mV dec⁻¹ and 100 mV dec⁻¹, in 0.5 M H₂SO₄ and 1.0 M KOH, respectively. The remarkable HER performance could be attributed to uniform ruthenium with the aid of highly dispersed ruthenium precursors (Ru–CAM) and subsequent annealing results in uniform ruthenium nanoparticles.

Highly dispersed ruthenium precursors via a supramolecular self-assembly assisted synthesis of uniform ruthenium nanoparticles with excellent HER performance.

Theophylline-bearing microspheres with dual features as a coordinative adsorbent and catalytic support for palladium ions

Polystyrenic microspheres in the sub 5 micrometer size range (micro-gel) with –CH₂Cl active sites were synthesized via the dispersion polymerization of 4-chloromethylstyrene, divinyl benzene and methoxy polyethylene glycol acrylate. Then, theophylline residues were introduced onto the polystyrenic microspheres via the substitution of the chloride in the –CH₂Cl group to prepare chelate type microspheres of μ-T2. It was found that the microspheres have co-continuous structures, monodispersed particle sizes, and excellent solvent and water wettability. Using the μ-T2 microspheres possessing theophylline residues, adsorption experiments involving the adsorption of palladium(ii), copper(ii) and platinum(iv) from acidic chloride media under both individual and mixed conditions were carried out and it was found that the μ-T2 microspheres exhibited excellent adsorption selectivity for palladium(ii) over copper(ii) and platinum(iv). It was also revealed that thiourea or ammonia solutions are the most effective in desorbing palladium ions from the microspheres. Despite being used in four adsorption–desorption cycles, the μ-T2 microspheres were still able to strongly adsorb palladium ions, with an adsorption of over 85%. In addition, the μ-T2 microspheres also showed palladium capturing ability even in very dilute palladium solutions (below 1.0 ppm). Interestingly, the μ-T2 microsphere-adsorbed palladium ions exhibited excellent catalytic activity in the Suzuki–Miyaura coupling reaction of bromobenzene and phenylboronic acid, yielding biphenyl in 100% under the conditions within 1 hour at 50 °C in water.

Sub 5 micrometer sized polystyrenic microspheres bearing theophylline residues were synthesized and used as adsorbent and catalytic support for palladium ions.

A highly efficient supramolecular adsorbent for precious metal: adsorption behavior of PdII by melamine cyanurate

Melamine cyanurate (M-CA) was found to be a high recoverable and selective supramolecular adsorbent for recovery of Pdⁱⁱ ion.

Preparation of a zwitterionic polymer based on l-cysteine for recovery application of precious metals

l-Cysteine-grafted polystyrene was synthesized from a cysteine-styrene monomer (Cys-Sty) in aqueous solution and used as a facile and selective high-recovery material for palladium(ii), platinum(iv), and gold(iii) ions from aqueous media.