Modification of mineral surfaces by adsorption of biosurfactants produced by Streptomyces sp

Effect of Sophorolipid Adsorption on the Coal Microstructure: Experimental and Wettability Mathematical Model Discussion

Green biosurfactants are emerging as a promising area of research. However, there is a limited focus on the adsorption and wetting characteristics of biosurfactants on coal dust. This study explores the effects of sophorolipid (SL) biosurfactants on the microstructure and wettability of different coalification degree coal. The microstructure parameters of SL adsorbed on coal dust were measured using a surface tensiometer, contact angle analyzer, and particle size analyzer. The results indicate that SL has the lowest critical surface tension, leading to a 9.25° decrease in the contact angle for low-rank bituminous coal (YZ-LRBC). Furthermore, SL significantly altered the particle size distribution of lignite (NM-LC) and YZ-LRBC. The pore size structure of SL-infiltrated coal dust was quantified using a specific surface area analyzer, revealing a decrease in the specific surface area and an increase in the average pore size. The infrared analysis demonstrated that SL permeation significantly increased the percentage of hydrophilic functional groups (hydroxyl structures) while reducing the hydrophobic functional groups (aliphatic hydrocarbon and aromatic structure). Based on the measured microstructure parameters, a regression equation for contact angle was established: [contact angle (°)] = 73.800 - 0.860 × [D10 (nm)] + 4.280 × [specific surface area (m2/g)]. Notably, the characteristic particle size D10 had a significant negative effect on the contact angle, while the specific surface area had a significant positive effect. These findings provide a theoretical foundation for the application of biosurfactants in water injection to reduce dust and improve the wetting efficiency.

Adsorption and immobilization of phosphorus from eutrophic seawater and sediment using attapulgite - Behavior and mechanism

The adsorption behavior of phosphorus on raw sediment (RS), attapulgite (AT), purified attapulgite (PAT) and AT/PAT-amended sediments conforms to the Langmuir, pseudo first-order kinetics and liquid film diffusion model. The adsorption process is spontaneous and monolayer adsorption, and the adsorption rate is mainly controlled by liquid film diffusion. The addition of attapulgite improved the adsorption capacity of phosphorus in the sediments of mariculture ponds. The results of long-term sediment core incubation showed that the average reduction rates of total phosphorus (TP) and soluble reactive phosphorus (SRP) in overlying water and SRP in pore water by adding 20% purified attapulgite (S/PAT20) were 62.11%, 70.83% and 56.32% respectively, and the phosphorus flux in sediments decreased by 53.81%. The addition of attapulgite reduces the risk of phosphorus release in sediments, and changes sediments from "source" to "pool". The specific surface area and pore volume of PAT increased to 203.254 cm²/g and 0.395 cm³/g respectively, but the phosphorus adsorption capacity was only increased by 2 times compared with AT (1431.3-2671.8 mg P/kg), indicating that the changes of mineral structure and chemical composition jointly determine the phosphorus adsorption effect. Adsorption mechanisms include physical adsorption, surface chemical precipitation, ligand effects, electrostatic attraction and ion exchange. Therefore, seeking modification methods with low energy consumption, low production cost, no damage to rod crystal, expansion of pore volume, increase of hydroxyl and other functional groups, and great retention of effective components are issues that need to be considered to improve the phosphorus adsorption capacity of attapulgite.

Rhamnolipids as Effective Green Agents in the Destabilisation of Dolomite Suspension

In this paper, we describe an application of mono- and dirhamnolipid homologue mixtures of a biosurfactant as a green agent for destabilisation of a dolomite suspension. Properties of the biosurfactant solution were characterised using surface tension and aggregate measurements to prove aggregation of rhamnolipids at concentrations much lower than the critical micelle concentration. Based on this information, the adsorption process of biosurfactant molecules on the surface of the carbonate mineral dolomite was investigated, and the adsorption mechanism was proposed. The stability of the dolomite suspension after rhamnolipid adsorption was investigated by turbidimetry. The critical concentration of rhamnolipid at which destabilisation of the suspension occurred most effectively was found to be 50 mg·dm-3. By analysing backscattering profiles, solid-phase migration velocities were calculated. With different amounts of biomolecules, this parameter can be modified from 6.66 to 20.29 mm·h-1. Our study indicates that the dolomite suspension is destabilised by hydrophobic coagulation, which was proved by examining the wetting angle of the mineral surface using the captive bubble technique. The relatively low amount of biosurfactant used to destabilise the system indicates the potential application of this technology for water treatment or modification of the hydrophobicity of mineral surfaces in mineral engineering.