The preparation of an environmentally friendly and efficient flocculant for solid-liquid separation in industrial wastewater is highly important. In this study, a novel cationic flocculant (AL-g-PAMA) was synthesized by a thermal initiation method using alkali lignin (AL) as the main chain and acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as the grafted side chains. The structure, thermal stability, and surface morphology of the copolymers were investigated by various characterization methods. The results indicated the successful synthesis of AL-g-PAMA. AL-g-PAMA was applied to improve solid-liquid separation in kaolin suspensions. The results showed that AL-g-PAMA had excellent flocculation-sedimentation and dewatering efficiency. When the dosage of AL-g-PAMA #5 was 600.0 g/t_(s), the thickness of the compressed layer was 2.2 cm, the floc settling velocity was 24.1 cm/min, and the transmittance of the supernatant was 84.0%. The moisture content of the filter cake decreased from 55.0% to 43.4% after treatment with AL-g-PAMA #5. The results of zeta potential and focused beam reflectance measurement (FBRM) analysis indicated that bridging and electroneutralization were the main flocculation mechanisms. Therefore, this study extends the potential for using lignin as a bioflocculant and provides a feasible approach to efficiently purify high-turbidity wastewater.

This study aimed to increase the ammonium nitrogen adsorption capacity of lignite using ultrafine grinding, aiming to reduce eutrophication in water bodies. Ammonium sulfate (NH₄)₂SO₄ was employed as a stand-in for ammonium nitrogen in water solutions. The lignite sample for adsorption was processed with varying milling times. Adsorption efficacy was assessed primarily through isothermal adsorption tests and other techniques. Additionally, the study delved into the adsorption mechanisms. The results demonstrate that lignite ground for 50 min follows monolayer adsorption, characterized by minimal pore size and reduced diffusion rates, thereby extending the time to reach equilibrium and maximizing adsorption. BET and SEM analyses show that coal powder is effectively ground by zirconia balls in a vertical stirring mill, diminishing its particle size and forming new micropores. Concurrently, larger native pores are transformed into mesopores and micropores, providing numerous sites for NH₄⁺ adsorption. XPS and FTIR analyses indicate an increase in exposed carbonaceous surfaces and oxygen-containing functional groups in ultrafine lignite. Ammonium ions replace hydrogen in carboxyl groups to form COONH₄, and hydrogen bonds may form between NH₄⁺ and C-O groups. Additionally, the electrostatic attraction between NH₄⁺ and the coal surface further enhances adsorption. It can be concluded that the physical grinding process increases the specific surface area and creates more active adsorption sites, which in turn, boosts NH₄⁺ adsorption capacity. The maximum equilibrium adsorption capacity is as high as 550 mg/g. This study suggests that ultrafine lignite is a promising material for treating ammonia-nitrogen wastewater.

Large-scale application of filled coal mining technology has long been limited by conditions such as the cost of filling. Compared to traditional filling materials, coal flotation tailing filling materials (CFTFM) offers advantages such as low cost and excellent performance. The Box–Behnken response surface method was used to investigate the influence of flotation tailing properties on the mechanical properties and hydration mechanisms of the filling material. Ash content, blending, and calcination temperature of the flotation tailings were used as the investigating factors, and uniaxial compressive strength (7d and 28d), slump, and the slurry water secretion rate of the filling material as the evaluation indicators. The results showed that the influence of the flotation tailings on the uniaxial compressive strength (28d) of CFTFM followed the order ash > calcination temperature > doping, with the interaction of ash and calcination temperature having a greater influence on the uniaxial compressive strength. The optimized pre-treatment conditions for the flotation tailings were 59% ash, 30% doping, a calcination temperature of 765 °C, and optimum uniaxial compressive strength of 7.02 MPa. The effect of flotation tailings on the exotherm of CFTFM hydration was determined using a TAM Air isothermal microcalorimeter, mainly in the induction and acceleration phases. Combined with SEM electron microscopy and IR FT-IR analysis of the hydration products, a descriptive model of the CFTFM hydration mechanism was established. CFTFM hydration can be described in three phases: diffusion, hydration, and hardening. The CFTFM prepared in this study is applicable to the integrated mining and charging synergistic mining technology, which can effectively reduce gangue lifting energy consumption and washing process waste, reduce the cost of filling, and can effectively achieve harmless, resourceful, and large-scale disposal of coal-based solid waste.

Hydrogenation of levulinic acid (LA) represents a significant approach for producing the high-value biomass-based platform compound γ-valerolactone (GVL). In this study, an efficient RuIr alloy bimetallic catalyst supported on SiC was synthesized and applied for the aqueous hydrogenation of LA into GVL under mild conditions. The RuIr/SiC catalyst exhibited high LA conversion and GVL selectivity (both > 99%) in water at 0.2 MPa H₂ pressure and 25 °C. The excellent performance is attributed to the synergistic interaction between Ru and Ir nanoparticles on the semiconducting SiC support. Furthermore, the catalytic activity of the RuIr/SiC alloy remained basically unchanged after five cycles, confirming the high stability of the bimetallic alloy catalyst.

In this work, the assembly behavior and structure of a compound collector with different carboxyl group positions at the low-rank coal (LRC)–water interface were investigated through coarse-grained molecular dynamics simulation (CGMD) combined with sum-frequency vibration spectroscopy (SFG). The choice of compound collector was dodecane +decanoic acid (D-DA) and dodecane +2-butyl octanoic acid (D-BA). CGMD results showed that the carboxyl group at the carbon chain’s middle can better control the assembly process between carboxylic acid and D molecules. SFG research found that the carboxyl group at the carbon chain’s termination had a greater impact on the displacement of the methyl/methylene symmetric stretching vibration peak, while the carboxyl group at the carbon chain’s middle had a greater impact on the displacement of the methyl/methylene asymmetric stretching vibration peak. The spatial angle calculation results revealed that the methyl group’s orientation angle in the D-BA molecule was smaller and the carboxyl group’s orientation angle in the BA molecule was bigger, indicating that D-BA spread more flatly on the LRC surface than D-DA. This meant that the assembled structure had a larger effective adsorption area on the LRC surface. The flotation studies also verified that the assembly behavior and structure of D-BA with the carboxyl group at the carbon chain’s middle at the LRC–water interface were more conducive to the improvement of flotation efficiency. The study of interface assembly behavior and structure by CGMD combined with SFG is crucial for the creation of effective compound collectors.