Sludge-derived iron-carbon material enhancing the removal of refractory organics in landfill leachate: Characteristics optimization, removal mechanism, and molecular-level investigation.

Mature landfill leachate is a refractory organic wastewater, and needs physical and chemical pretreatments contemporaneously, e.g. iron-carbon micro-electrolysis (IC-ME). In this study, a novel iron-carbon (Fe-C) material was synthesized from waste activated sludge to be utilized in IC-ME for landfill leachate treatment. The pyrolysis temperature, mass ratio of iron to carbon, and solid-liquid ratio in leachate treatment were optimized as 900 °C with 1.59 and 34.7 g/L. Under these optimal conditions, the chemical oxygen demand (COD) removal efficiency reached 79.44 %, which was 2.6 times higher than that of commercial Fe-C material (30.1%). This excellent COD removal performance was indicated to a better mesoporous structure, and uniform distribution of zero-valent iron in novel Fe-C material derived from sludge. The contribution order of COD removal in IC-ME treatment for landfill leachate was proven as coagulation, adsorption, and redox effects by a contrast experiment. The removal of COD includes synthetic organic compounds, e.g. carcinogens, pharmaceuticals and personal care products. The contents of CHO, CHON, and CHOS compounds of dissolved organic matter (DOM) in the leachate were decreased, and both the molecular weight and unsaturation of lipids, lignin, and tannic acids concentration were also reduced. Some newly generated small molecular DOM in the treated leachate further confirmed the existence of the redox effect to degrade DOM in leachate. The total cost of sludge-derived Fe-C material was only USD$ 152.8/t, which could save 76% of total compared with that of commercial Fe-C materials. This study expands the prominent source of Fe-C materials with excellent performance, and deepens the understanding of its application for leachate treatment.

Functionalized poly(arylene ether sulfone) containing hydroxyl units for the fabrication of durable, superhydrophobic oil/water separation membranes.

The stability of superhydrophobicity is crucial for the long-term application of an oil/water separation membrane in harsh environments such as high temperatures and various aggressive solvents. However, achieving such a stable superhydrophobic membrane remains a challenge. In this study, high performance fibrous oil/water separation membranes with a highly stable superhydrophobicity were fabricated by designing a functional polymer containing hydroxyl units. The reaction of hydroxy groups in poly(arylene ether sulfone) with octadecyltrichlorosilane (OTS) produces stable covalent interactions, which greatly enhance the stability of OTS on the PAES-OH (polyarylene ether sulfone containing hydroxy units) fibrous membrane fabricated by electrospinning, thus improving the stability of superhydrophobicity of the membrane. The stability of the OTS layer was characterized by FT-IR, SEM and water contact angle measurement. The results suggest that OTS is highly stable on a PAES-OH membrane, while OTS on a polyethersulfone (PES) fibrous membrane is detached from the fiber during ultrasonic cleaning. The obtained membrane is superhydrophobic, with a water contact angle (CA) as high as 159.2° and a threshold sliding angle (TSA) as low as 7.8° even after ultrasonic cleaning for 3 h. In addition, the oil/water separation experiments indicate that this membrane has an excellent performance in the separation of oil from oil/water mixtures, and oil/water emulsions: the gravity driven flux is 7260-8720 L (m2 h)-1 and the water rejection is over 99%. This study provides a new approach for fabricating oil/water separation membranes with highly stable superhydrophobic properties from the perspective of designing new polymers.

A rapid deposition of polydopamine coatings induced by iron (III) chloride/hydrogen peroxide for loose nanofiltration.

Mussel-inspired polydopamine (PDA) coatings have received widespread concern due to the advantages of eco-friendliness, adhesion nature, and film-forming feasibility. However, self-polymerization of dopamine assisted by air-oxidation under alkaline condition is time-consuming, and the ensuing uneven PDA coatings restrict their applications. In this study, we proposed a rapid PDA deposition triggered by a facile system of iron (III) chloride/hydrogen peroxide (FeCl3/H2O2) under acidic condition. The oxygen-radical species generated by FeCl3/H2O2 largely promote covalent polymerization and deposition rate of dopamine. This not only considerably shortens the deposition time of PDA, but also improves the stability of PDA coatings, combined with the chelation of Fe ions in PDA matrices. SEM, AFM, XPS, zeta potential and water contact angle analyses confirmed the formation of a hydrophilic, smooth, and negatively charged PDA layer onto several membrane substrates. Herein, PDA-coated hydrolyzed polyacrylonitrile membranes yield a remarkable NF performance with superior dye retentions (direct red 23: 98.6%, Congo red: 99.0%, reactive blue 2: 98.2%) and a high water permeability (17.5 L m-2 h-1 bar-1). Furthermore, a low salt rejection (NaCl: 5.6%) of PDA-modified membranes demonstrates their great potential in fractionation of dye/salt mixtures. Meanwhile, the PDA-modified membranes show an excellent organic fouling resistance and a long-term stability. This facile, environmental-friendly method provides a rapid PDA deposition onto various substrates for a wide range of applications, including filtration membranes.