Removal of Cr (VI) from aqueous solution by activated charcoal derived from Sapindus trifoliate L fruit biomass using continuous fixed bed column studies

Carbon-based adsorbents as proficient tools for the removal of heavy metals from aqueous solution: A state of art-review emphasizing recent progress and prospects

Carbon-centric adsorbents (CCA) are diverse forms, from simple biochar (BC) to graphene derivatives, carbon nanotubes (CNTs), and activated carbon (AC), which have been vastly explored for their removal of a plethora of pollutants, including heavy metals (HM). The prominent features of CCA are their operational attributes like extensive surface area, the occurrence of flexible surface functional groups, etc. This work offers a comprehensive examination of contemporary research on CCA for their superior metal removal aptitude and performances in simulated solutions and wastewater flows; via portraying the recent research advances as an outlook on the appliances of CACs for heavy metal adsorption for removal via distinct forms like AC, BC, Graphene oxide (GO), and CNTs. The bibliometric analysis tool was employed to highlight the number of documents, country-wise contribution, and co-occurrence mapping based on the Scopus database. The coverage of research works in this review is limited to the last 5 years (2017-2021) to highlight recent progress and prospects in using CCAs such as AC, BC, GO, and CNTs to remove HM from aqueous media, which makes the review unique. Besides an overview of the common mechanisms of CACs, the future scope of CAC, especially towards HM mitigation, is also discussed in this review. This review endorses that further efforts should be commenced to enhance the repertory of CCAs that effectively eliminate multiple targeted metals in both simulated and real wastewater.

Oleic Acid-Tailored Geopolymer Microspheres with Tunable Porous Structure for Enhanced Removal from Tetracycline in Saline Water

Tetracycline (TC) in the water body poses a huge threat to the ecological environment. There is a great challenge to develop highly efficient, green, low-cost and reusable adsorbents for TC removal from saline water. Herein, metakaolin-based geopolymer microspheres (MM) modified by oleic acid were proposed for the enhanced adsorption of TC from saline water. Experimental and characterization results showed that the introduction of oleic acid into the MM effectively adjusted the specific surface area, pore volume and zeta potential of the MM, thus accelerating the adsorption rate and enhancing the TC adsorption capacity of the MM. The adsorption process fitted well to the pseudo-second-order kinetic and Langmuir isothermal models. The Langmuir adsorption capacity of TC by the optimal MM, namely MM3 (0.3%, oleic acid), reached 645.7 mg·g−1 at 298 K, which was higher than many reported adsorbents. The adsorption process was endothermic and spontaneous. The MM3 had good adsorption performance of TC from saline water and regeneration performance. Moreover, the breakthrough curves of the MM3 in a column system were correlative with the Thomas and Yoon–Nelson models. The adsorption mechanisms of TC by the MM3 involved Van der Waals forces, electrostatic interactions, hydrogen–bonding interactions, and ion exchange.