Hydrothermal Carbonization of Residual Algal Biomass for Production of Hydrochar as a Biobased Metal Adsorbent

A review on adsorption of heavy metals from wastewater using carbon nanotube and graphene-based nanomaterials

The rampant rise in world population, industrialization, and urbanization expedite the contamination of water sources. The presence of the non-biodegradable character of heavy metals in waterways badly affects the ecological balance. In this modern era, the unavailability of getting clear water as well as the downturn in water quality is a major concern. Therefore, the effective removal of heavy metals has become much more important than before. In recent years, the attention to better wastewater remediation was directed towards adsorption techniques with novel adsorbents such as carbon nanomaterials. This review paper primarily emphasizes the fundamental concepts, structures, and unique surface properties of novel adsorbents, the harmful effects of various heavy metals, and the adsorption mechanism. This review will give an insight into the current status of research in the realm of sustainable wastewater treatment, applications of carbon nanomaterials, different types of functionalized carbon nanotubes, graphene, graphene oxide, and their adsorption capacity. The importance of MD simulations and density functional theory (DFT) in the elimination of heavy metals from aqueous media is also discussed. In addition to that, the effect of factors on heavy metal adsorption such as electric field and pressure is addressed.

Effective removal of Ni(II) ions from its aqueous solution by utilizing Euphorbia thymifolia as an adsorbent

Since the electroplating and alloy industries continuously pollute water resources, this paper presents a novel adsorbent to adsorb nickel ions from aqueous solutions prepared in the lab. Chhotidudhi, a creeping weed that is commonly called Euphorbia thymifolia, was used as an adsorbent in its pristine and activated forms. In order to characterize the structure, morphology, and thermal properties of ground Euphorbia thymifolia (ETR) and activated Euphorbia thymifolia (ETA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal gravimetric analysis (TGA) were used. It was observed that the FTIR spectrum showed different functional groups, such as OH, CH, CO, CN, and CF, which indicated a strong bond with metals. XRD and SEM revealed that the adsorbent is amorphous with a porous structure. Additionally, different adsorbent doses, contact times, pH, concentrations, and temperatures were investigated. Approximately 2 h was required for effective adsorption with an initial concentration of 20 mg/L, pH 7, adsorption dose of 20 mg, and temperature of 303 K. At optimized conditions, the adsorption capacity for ETR and ETA was 52.4 mg/g and 109.05 mg/g, respectively, and the removal efficiency was 81.6% and 93.8%. Both Langmuir and pseudo-second-order reactions matched the experimental results perfectly.

Hydrothermal processing of microalgal biomass: Circular bio-economy perspectives for addressing food-water-energy nexus

Hydrothermal processing of microalgae is regarded as a promising technology to generate multitude of energy based and value-added products. The niche of hydrothermal technologies is still under infancy in terms of the technical discrepancies related to research and development. Thus, the present review critically surveyed the recent advancements linked to the influencing factors governing the algal hydrothermal processing in terms of the product yield and quality. The sustainability of hydrothermal technologies as a standalone method and in broader aspects of circular bio-based economy for energy and value-added platform chemicals are comprehensively discussed. Process optimization and strategic integration of technologies has been suggested to improve efficiency, with reduced energy usage and environmental impacts for addressing the energy-food-water supply chains. Within the wider economic transition and sustainability debate, the knowledge gaps identified and the research hotspots fostering future perspective solutions proposed herewith would facilitate its real-time implementation.