Use of porous materials to remove oil contaminants from water

Waste Mineral Wool and Its Opportunities-A Review

Massive waste rock wool was generated globally and it caused substantial environmental issues such as landfill and leaching. However, reviews on the recyclability of waste rock wool are scarce. Therefore, this study presents an in-depth review of the characterization and potential usability of waste rock wool. Waste rock wool can be characterized based on its physical properties, chemical composition, and types of contaminants. The review showed that waste rock wool from the manufacturing process is more workable to be recycled for further application than the post-consumer due to its high purity. It also revealed that the pre-treatment method—comminution is vital for achieving mixture homogeneity and enhancing the properties of recycled products. The potential application of waste rock wool is reviewed with key results emphasized to demonstrate the practicality and commercial viability of each option. With a high content of chemically inert compounds such as silicon dioxide (SiO₂), calcium oxide (CaO), and aluminum oxide (Al₂O₃) that improve fire resistance properties, waste rock wool is mainly repurposed as fillers in composite material for construction and building materials. Furthermore, waste rock wool is potentially utilized as an oil, water pollutant, and gas absorbent. To sum up, waste rock wool could be feasibly recycled as a composite material enhancer and utilized as an absorbent for a greener environment.

Bio-inspired anchoring of amino-functionalized multi-wall carbon nanotubes (N-MWCNTs) onto PES membrane using polydopamine for oily wastewater treatment

The major problem that limits the utilization of PES membranes in treatment of oily wastewater is the drastic irreversible membrane fouling due to the attachment of oil droplets onto the membrane surface. The goal of this study was to develop a novel, fast and facile post-functionalization of polydopamine (PDA) coated membranes using pre-synthesized nanoparticles for fabrication of novel organic-inorganic hybrid recoverable membranes with high hydrophilicity and underwater oleophobicity. Here, bio-inspired technique was studied because the membrane technology could separate small oil droplets (even <10 µm) with high performance if faced little fouling phenomena during the treatment process. The amino-functionalized multi-wall carbon nanotubes (N-MWCNTs) were anchored onto the PDA coated PES membranes. The membranes characteristics, with specific focus on surface morphology and wettability were investigated. The newly developed PES/PDA/N-MWCNTs membranes showed an enhanced flux (~1086%) compared to the unmodified PES membrane. This enhancement was attributed to the high hydrophilic and underwater oleophobic properties, which were found to alleviate the effect of fouling. The total fouling ratio (R_t) of the PES/PDA/N-MWCNTs membrane was 22.35%, which was far lower than that of the unmodified PES membrane (98.38%). Meanwhile, most of the fouling was reversible for the former with the remaining (irreversible fouling) of 18.08%. It was concluded that cake filtration is the dominant fouling mechanism of the PES/PDA/N-MWCNTs membranes due to their average pore diameter. The modified membranes showed high oil rejection (>99%) so that the obtained clean water with oil concentration lower than 5 ppm met the wastewater discharge standard recommendations. Also, evaluation of the PES/PDA/N-MWCNT membrane in cross-flow filtration showed its antifouling properties in the long-term application (16 h).

Application of a new type of Si–Al porous clay material as a solid phase support for immobilizing Acidovorax sp. PM3 to treat domestic sewage

A novel Si–Al porous clay material W (reprocessed from ceramic waste) was used for Acidovorax sp. strain PM3 immobilization to promote the growth of strains and improve nitrogen and phosphorus removal performance in water treatment systems. The porous clay material W was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy indicating that porous clay material W was a type of mullite with 63.52 m2/g specific surface area. After immobilization, the maximum biomass increased 2.7 times the specific growth rate and the removal rates of chemical oxygen demand (COD), ammonia (NH4+–N), and total phosphorus (TP) by the immobilized PM3 were 42.99, 29.19, and 11.76% higher than the free strain after 24 h. The Monod equation showed that the growth rate and processing speed of immobilized PM3 increased. The maximum adsorption capacities of COD and NH4+–N onto porous clay material W were 2.33 and 0.32 mg/g on the basis of Langmuir isotherm. The removal capacities of COD, NH4+–N, and TP by the immobilized PM3 were 588.24, 20.37, and 5.06 mg/l, respectively, as shown by kinetic studies. These results demonstrated that porous clay material W could improve the efficiency of microbial nitrogen and phosphorus removal, and the immobilized microorganism system could effectively treat domestic sewage. The adsorption isotherms can well describe the adsorption process. The maximum adsorption capacity of COD and NH4+–N on porous clay material W is 2.33 and 0.32 mg/g, respectively. Kinetic studies showed that the removal capacity of immobilized PM3 to COD, NH4+–N, and TP was 58.824, 20.37, and 5.06 mg/l, respectively.

A facile approach to ultralight and recyclable 3D self-assembled copolymer/graphene aerogels for efficient oil/water separation

In this paper, a facile approach was developed for highly effective oil/water separation by incorporating of the dimethyldiallylammonium chloride acrylamide polymer (P(AM-DMDAAC)) into graphene aerogels. The functionalized 3D graphene aerogel integrated a series of excellent physical properties, including low density (11.4 mg/cm³), large specific surface area (206.591 m²/g), and great hydrophobicity (contact angle of 142.7°). The modified aerogel showed excellent adsorption capacity for oils and organic solvents (up to 130 g/g). The saturation can be reached in a short time and the adsorption capacity remained nearly unchanged after repeated heating cycles. Meanwhile, we found a simple method to achieve controlled wettability transition of P(AM-DMDAAC)/graphene aerogels (PGAs) by changing the pH values. The hydrophobic PGA prepared at pH 2.03 showed outstanding oil/water separation performance (130 g/g). As the pH increased, the oil adsorption capabilities of PGAs decreased slightly, but the adsorption performance for the hydrophilic organic dye was significantly improved. Therefore, as a recyclable and efficient water purification material, the sustainable and environment-friendly polymer-modified graphene aerogel has great application potential.

Integrated interrogation of causes of membrane fouling in a pilot-scale anoxic-oxic membrane bioreactor treating oil refinery wastewater

Studies on membrane fouling during treatment of oil refinery wastewater (ORW) via membrane bioreactor (MBR) are currently lacking, and associated fouling challenges are largely undocumented. Using advanced chemical and Illumina sequencing approach, we investigated the complex bio-physiochemical interactions responsible for foulant-membrane interactions during treatment of ORW. After nearly 2 months of the MBR operation, COD removal reached maximal of 97.15 ± 1.85%, while oil and grease removal was maintained at 96.6 ± 2.6%, during the treatment duration. Most of the less or non-biodegradable oil moieties (>0.5 μm) progressively accumulated on the membrane as the influent oil concentration increased. Presence of relatively higher unsaturated extracellular polymers (100.6 mg/g VSS) like fulvic acid and aromatic-like compounds at high volumetric loading (~18.7 kg COD/m³/d), enhanced the adsorption of chemical elements (Fe = 88.9, Al = 63.4, and Ce = 0.56 mg/g dry-sludge, respectively). Moreover, shift in microbial community structure to hydrocarbon-utilizing and metals-tolerating genera, as Comamonas and Rhodanobacter, respectively, uncovers major membrane colonizers in ORW treatment via MBR.