Synthesis of core–shell activated carbon/CaO composite from Ficus Nitida leaves, as an efficient adsorbent for removal of methylene blue

Fabrication of spirulina based activated carbons for wastewater treatment

The lack of safe drinking water is among the main problems to be faced by many areas of the world due to climate change, unrestrained population increases, and unsustainable usage of water sources. Therefore, research projects focusing on water quality, pollution, and control for sustainable water sources are in high demand to manage any unexpected changes in water sources. Drinking water sources may be contaminated with organic and inorganic chemicals, disinfection by-products, and microorganisms. Different treatment processes to remove these contaminants from water may be limited because of their high costs and time-consuming or require a multiple-barrier approach to improving performance. Therefore, there is a great need to develop an effective process for removing impurities. The primary objective of this study is to assess the effectiveness of algae-based activated carbons and develop a unique, low-cost sustainable process for wastewater treatment. Activated carbons were produced from pelletised algae powder using carbonisation and chemical activation. Chemical activation was carried out with calcium chloride (CaCl2) and zinc chloride (ZnCl2) as chemical agents. Furthermore, Brunauer-Emmett-Teller (BET) along with scanning electron microscopy (SEM) techniques were used to analyse the morphology, surface area, as well as the porosity of the prepared activated carbons to build a water column filter. Based on the results, algae-based carbon with CaCl2 activation provided a better surface area (197.7486 m2/g) and cumulative pore volume (0.105284 cm3/g). The filtration process using algae-based activated carbon can be a promising technique for water treatment with some further improvement and modifications.

Potential use of dry powder of Vossia cuspidata (Roxb.) Griff. rhizomes and leaves in methylene blue dye remediation

Phytoremediation is a promising, cost-effective, and eco-friendly process for wastewater treatment. Herein, the dry biomasses of Vossia cuspidata (Roxb.) Griff. leaves (PL) and rhizomes including aerial stems (PR) were used to effectively remediate methylene blue (MB) dyes. Interestingly, the adsorption uptake and removal efficiency of MB by PR were higher than those of PL; exceeding 97 and 91% in 35 and 25 min for 0.1 and 0.4 g/L MB, respectively. The MB diffusion within the PL and PR was insignificant and the adsorption kinetics was principally controlled by the surface MB-adsorbent interaction, as consistently approved by the pseudo-second order kinetic model. In addition, the adsorption increased rapidly with the plant dosage with high dependence on the initial MB concentration. Moreover, the impact of shaking speed on the adsorption was minor but temperature played a critical role where the highest efficiencies were recorded at 30 and 40 °C on PL (91.9%) and PR (93.3%), respectively. The best removal efficiencies were attained with PR at pH 6, but with PL at pH 8. The Temkin isotherm could perfectly simulate the experimental data (R2 > 0.97); suggesting a linear decrease of the adsorption heat of MB with the plant coverage.

Phytoremediation Potential of Selected Ornamental Woody Species to Heavy Metal Accumulation in Response to Long-Term Irrigation with Treated Wastewater

Arid and semiarid environments of Mediterranean countries suffer from scarcity of water resources, which limits their agriculture productivity. Using treated wastewater (TWW) is considered an alternative strategy for irrigation purposes in such areas. However, TWW contains substantial levels of heavy metals (HMs) and contaminants that pollute the environment and soil. The aim of this study is to evaluate the phytoremediation potential of six selected woody tree species under long-term irrigation with TWW. The concentration, bioaccumulation factor (BFC), translocation factor (TF), and comprehensive bioconcentration index (CBCI) of HMs were measured in the various parts (roots, bark, and leaves) of the studied tree species. The results show a general pattern of mineral accumulation in the roots and low translocation to the areal parts of various species. Cupressus sempervirens, which is a native species in Mediterranean environments, had higher TF values for Fe, Mn, Cu, Cr, Cd, and Pb metals in its areal parts compared to other tree species. The study shows that Ficus nitida has the potential to be a hyperaccumulator for Cd in its bark, with a TF value that exceeds 12. Deciduous trees species (Populus nigra and Robinia pseudoacacia) were found to have high TF values for Ni and Cd toward their areal parts, whereas a higher TF for Cr (1.21) was only found in P. nigra bark. Cupressus sempervirens had, significantly, the highest bark and leaf CBCI values (0.83 and 0.82, respectively), whereas Ficus nitida had the second-highest values in the bark and leaves (0.56 and 0.51, respectively). Therefore, Cupressus sempervirens and Ficus nitida are considered good hyperaccumulators for various HMs, and can be used for phytoremediation activities in polluted areas.

Fabrication of Highly Microporous Structure Activated Carbon via Surface Modification with Sodium Hydroxide

The aim of this study was to select the optimal conditions for the carbonization process followed by surface modification treatment with sodium hydroxide (NaOH) to obtain a highly microporous activated carbon structure derived from palm kernel shells (PKS) and coconut shells (CS). The effects of the carbonization temperature and NaOH concentration on the physiochemical properties, adsorption capability, specific surface area, surface morphology, and surface chemistry of PKS and CS were evaluated in this study. The results show that surface-modified activated carbons presented higher surface area values (CS: 356.87 m2 g-1, PKS: 427.64 m2 g-1), smaller pore size (CS: 2.24 nm, PKS: 1.99 nm), and larger pore volume (CS: 0.34 cm3 g-1, PKS: 0.30 cm3 g-1) than the untreated activated carbon, demonstrating that the NaOH surface modification was efficient enough to improve the surface characteristics of the activated carbon. Moreover, surface modification via 25% NaOH greatly increases the active functional group of activated carbon, thereby directly increasing the adsorption capability of activated carbon (CS: 527.44 mg g-1, PKS: 627.03 mg g-1). By applying the NaOH post-treatment as the ultimate surface modification technique to the activated carbon derived from PKS and CS, a highly microporous structure was produced.

Advances in decontamination of wastewater using biomass-basedcomposites: A critical review

Contaminant removal from wastewater using natural biosorbents has been widely studied as a suitable and environmentally benign alternative for conventional techniques. Currently, researchers are working on various biomass-based composites for wastewater remediation to improve the performance of natural biosorbents. This review takes into focus a wide range of biomass-based composites like hydrogel composites, metal oxide composites, magnetic composites, polymer composites, carbon nanotubes (CNTs) and graphene composites, metal organic framework composites (MOFs) and clay composites for the removal of various contaminants from wastewater. It is evident from the literature survey that the composite fabrication involves the modification of morphological and textural features of the biomass which results in significant enhancement of adsorption capacity. Apart from this, regeneration of the used biomass-based composite is also studied in depth in order to overcome the problem of solid waste generation. This review would prove to be beneficial for researchers who are currently focusing on the development of cost-effective, easily available, recyclable biomass-based composites with enhanced adsorption capacities for wastewater treatment.