Biomass derived P−doped activated carbon as nanostructured mesoporous adsorbent for chromium(VI) pollutants with pronounced functional efficiency and recyclability

The adsorption mechanism of arsenic in flue gas over the P-doped carbonaceous adsorbent: Experimental and theoretical study

The utilization of carbon-based sorbent has gained extensive attention for arsenic removal from flue gas due to their high specific surface area, sufficient active sites and abundant sources. This study proposes that the addition of phosphorous could be used as an effective promoter for the activation and modification of carbonaceous sorbent to enhance their arsenic fixation capacity. Both experimental and density functional theory (DFT) methods were employed to systematically investigate the adsorption characteristics of arsenic over different carbon based sorbents. The results reveal that the modification of H3PO4 generated C-O-P, C-P-O, and C3-P-O functional groups on the surface of activated carbon, and the adsorption ability of H3PO4-modified activated carbon for gaseous arsenic was significantly improved compared with the untreated activated carbon. DFT calculations indicate that unsaturated C atoms on carbonaceous surface served as active sites during arsenic adsorption, the electronegativity of which could be enhanced by phosphorous functional group, thereby facilitating the adsorption of gaseous arsenic species. Additionally, the positive effect of the phosphorous functional group on arsenic adsorption is more pronounced on zigzag carbonaceous surface than on armchair carbonaceous surface. This work provides a theoretical basis of the development of high-performance biochar preparation for arsenic adsorption by explaining the promoting effect of phosphorous functional group on gaseous arsenic adsorption on carbonaceous surface.

Adsorption of heavy metal onto biomass-derived activated carbon: review

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Adsorption of Hexavalent Chromium Using Activated Carbon Produced from Sargassum ssp.: Comparison between Lab Experiments and Molecular Dynamics Simulations

Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The transformation of Sargassum-an invasive brown macroalga-into activated carbon (AC) via phosphoric acid thermochemical activation was explored in an effort to increase the value of Sargassum seaweed biomass. Several techniques (nitrogen adsorption, pHPZC, Boehm titration, FTIR and XPS) were used to characterize the physicochemical properties of the activated carbons. The SAC600 3/1 was predominantly microporous and mesoporous (39.6% and 60.4%, respectively) and revealed a high specific surface area (1695 m2·g-1). To serve as a comparison element, a commercial reference activated carbon with a large specific surface area (1900 m2·g-1) was also investigated. The influence of several parameters on the adsorption capacity of AC was studied: solution pH, solution temperature, contact time and Cr(VI) concentration. The best adsorption capacities were found at very acid (pH 2) solution pH and at lower temperatures. The adsorption kinetics of SAC600 3/1 fitted well a pseudo-second-order type 1 model and the adsorption isotherm was better described by a Jovanovic-Freundlich isotherm model. Molecular dynamics (MD) simulations confirmed the experimental results and determined that hydroxyl and carboxylate groups are the most influential functional groups in the adsorption process of chromium anions. MD simulations also showed that the addition of MgCl2 to the activated carbon surface before adsorption experiments, slightly increases the adsorption of HCrO4- and CrO42- anions. Finally, this theoretical study was experimentally validated obtaining an increase of 5.6% in chromium uptake.