Biodegradable lignocellulosic porous materials: Fabrication, characterization and its application in water processing

Recoverable cellulose composite adsorbents for anionic/cationic dyes removal

GO/HEC/PGDE/Fe₃O₄ materials were successfully fabricated using environmentally-friendly hydroxyethyl cellulose (HEC), poly(ethylene glycol) diglycidyl ether (PGDE), graphene oxide (GO) and magnetic Fe₃O₄. Systematic investigations were completed to explore the influences of GO content in GO/HEC/PGDE/Fe₃O₄ and adsorption conditions on the adsorptions of cationic dyes (methylene blue (MB), crystal violet (CV)) and anionic dye acid blue 25 (AB-25). The increase of GO content can remarkably improve the adsorption capacity of GO/HEC/PGDE/Fe₃O₄ for the dyes. The three kinetic, four isothermic and three thermodynamic models were investigated to reveal the adsorption behaviors of the dyes. The formation of HEC/PGDE/Fe₃O₄ and adsorption mechanisms of the dyes by GO/HEC/PGDE/Fe₃O₄ were suggested. The GO/HEC/PGDE/Fe₃O₄ endowed with easy-fabrication, eco-friendly feature, efficient adsorption capacity of anionic/cationic dyes, convenient separation and reusability has potential applications in wastewater purification industry.

Biomass utilization and production of biofuels from carbon neutral materials

The availability of organic matters in vast quantities from the agricultural/industrial practices has long been a significant environmental challenge. These wastes have created global issues in increasing the levels of BOD or COD in water as well as in soil or air segments. Such wastes can be converted into bioenergy using a specific conversion platform in conjunction with the appropriate utilization of the methods such as anaerobic digestion, secondary waste treatment, or efficient hydrolytic breakdown as these can promote bioenergy production to mitigate the environmental issues. By the proper utilization of waste organics and by adopting innovative approaches, one can develop bioenergy processes to meet the energy needs of the society. Waste organic matters from plant origins or other agro-sources, biopolymers, or complex organic matters (cellulose, hemicelluloses, non-consumable starches or proteins) can be used as cheap raw carbon resources to produce biofuels or biogases to fulfill the ever increasing energy demands. Attempts have been made for bioenergy production by biosynthesizing, methanol, n-butanol, ethanol, algal biodiesel, and biohydrogen using different types of organic matters via biotechnological/chemical routes to meet the world's energy need by producing least amount of toxic gases (reduction up to 20-70% in concentration) in order to promote sustainable green environmental growth. This review emphasizes on the nature of available wastes, different strategies for its breakdown or hydrolysis, efficient microbial systems. Some representative examples of biomasses source that are used for bioenergy production by providing critical information are discussed. Furthermore, bioenergy production from the plant-based organic matters and environmental issues are also discussed. Advanced biofuels from the organic matters are discussed with efficient microbial and chemical processes for the promotion of biofuel production from the utilization of plant biomasses.

Current State of Porous Carbon for Wastewater Treatment

Porous materials constitute an attractive research field due to their high specific surfaces; high chemical stabilities; abundant pores; special electrical, optical, thermal, and mechanical properties; and their often higher reactivities. These materials are currently generating a great deal of enthusiasm, and they have been used in large and diverse applications, such as those relating to sensors and biosensors, catalysis and biocatalysis, separation and purification techniques, acoustic and electrical insulation, transport gas or charged species, drug delivery, and electrochemistry. Porous carbons are an important class of porous materials that have grown rapidly in recent years. They have the advantages of a tunable pore structure, good physical and chemical stability, a variable specific surface, and the possibility of easy functionalization. This gives them new properties and allows them to improve their performance for a given application. This review paper intends to understand how porous carbons involve the removal of pollutants from water, e.g., heavy metal ions, dyes, and organic or inorganic molecules. First, a general overview description of the different precursors and the manufacturing methods of porous carbons is illustrated. The second part is devoted to reporting some applications such using porous carbon materials as an adsorbent. It appears that the use of porous materials at different scales for these applications is very promising for wastewater treatment industries.

Evaluation of the inter-particle interference of cellulose and lignin in lignocellulosic materials

The inter-particle interference of lignocellulosic materials describes the order of the macromolecules at a larger size scale, which can give information about the pore structure, and interface of cellulose and lignin. The pore structure and interface influence the rate of enzymatic hydrolysis and thermal decomposition in cellulosic ethanol manufacturing. In this study, the inter-particle interference of cellulose and lignin of three major categories of lignocellulosic materials: wood-based (cedar and oak), energy crop (bamboo), and agricultural or forestry waste (palm) were evaluated. Scanning electron microscopy (SEM) reveals morphological irregularities in the case of bamboo and palm, which may form nucleation sites for faster accessibility to enzyme molecules. Small-angle X-ray scattering (SAXS) shows increased power-law exponent for palm, suggesting a less clustered structure, which was consistent with the rough surface morphology as detected by the SEM. Differential Scanning Calorimetry (DSC) showed a higher temperature maximum for cedar and oak, which is indicative of higher intermolecular forces within their organic compounds, and could result in slower disintegration of the macromolecules during biochemical processing. This study will help to estimate the activity of the macromolecules and absorption capacity of lignocellulosic materials during biochemical processing.

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.

Calcined Mussel Shell Powder (CMSP) via Modification with Surfactants: Application for Antistatic Oil-Removal

Biomass is known to efficiently adsorb pollutants from wastewater. In this paper, we demonstrated that a new antistatic oil-cleaning material can be prepared and assembled by using two surfactants, alkyl polyglucosides (APG) and dimethyl octadecyl hydroxy ethyl ammonium nitrate (SN), to modify calcined mussel shell powder (CMSP) through a two-step hydrotherm-assisted adsorption. The pore size and structure of CMSP was measured by BET and a contact angle meter was used to characterize the surface wetting ability. XRD, FTIR, XPS, SEM, TEM, and HRTEM were employed to determine the surface structure of CMSP modified by surfactants APG and SN (MMO). In order to further characterize properties of the surface morphology and crystal structure, the HRTEM was employed to show that the MMO surface had a single crystal structure: calcite, with a crystal plane spacing of 0.2467 nm. The surface of MMO appeared to be fluffy and disperse. The antistatic and degreasing ability of as-prepared samples (MMO) was evaluated by a ZC-36 high resistance meter and BD-457 whiteness meter. The results showed that when the calcination temperature of CMSP reached 1000 °C, and the addition amount of APG and SN was 0.8 g and 0.16 g, it had an optimum antistatic effect with a surface resistivity (Rs) of 1.35 × 10⁸ Ω, and a detergency rate to oil of 17.35%. This study aims to embrace a green solution to reduce environmental pressure and make use of waste, which is of great significance to environmental protection.