Preparation, characterization and Cr(VI) adsorption evaluation of NaOH-activated carbon produced from Date Press Cake; an agro-industrial waste.

Chromium exists mainly in two forms in environmental matrices, namely, the hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium. While Cr(III) is a micronutrient, Cr(VI) is a known carcinogen, and that warrants removal from environmental samples. Amongst the removal techniques reported in the literature, adsorption methods are viewed as superior to other methods because they use less chemicals; consequently, they are less toxic and easy to handle. Mitigation of chromium using adsorption methods has been achieved by exploiting the physical, chemical, and biological properties of Cr(VI) due to its dissolution tendencies in aqueous solutions. Many adsorbents, including synthetic polymers, activated carbons, biomass, graphene oxide, and nanoparticles as well as bioremediation, have been successfully applied in Cr(VI) remediation. Initially, adsorbents were used singly in their natural form, but recent literature shows that more composite materials are generated and applied. This review focused on the recent advances, insights, and project future directions for these adsorbents as well as compare and contrast the performances achieved by the mentioned adsorbents and their variants.

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Recent advances in hexavalent chromium removal from aqueous solutions by adsorptive methods

The presence of chromium in industrial effluents has become a huge problem worldwide as hexavalent chromium is highly toxic to animals due to its ability to generate reactive oxygen species in cells. The trivalent state of chromium, on the other hand, is significantly less toxic and also serves as an essential element in trace amounts. When industries such as electroplating, tannery, dyeing and others release their effluents into water bodies, hexavalent chromium enters the food chain and, consequently, reaches humans in a biomagnified form. Many remediation processes for removal of hexavalent chromium have been researched and reviewed extensively. These include chemical reduction to trivalent chromium, solvent extraction, chelation and adsorption, among others. It has been generally concluded that adsorption (and/or subsequent reduction) of hexavalent chromium is the best method. However, relatively little is known about the potential of using nanoparticles as adsorbents for the removal of hexavalent chromium from industrial effluents. This method of nanoremediation is more effective than conventional remediation methods and is cost-effective for the industry in the long run. This article reviews the various remediation methods of hexavalent chromium, with emphasis on the field of nanoremediation.

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Removal of chromium from industrial effluents using nanotechnology: a review

Preparation of nitrogen-doped porous carbon material by a hydrothermal-activation two-step method and its high-efficiency adsorption of Cr(VI)

Designing a stable, selective, and efficient adsorbent for the removal of pollutants like chromium poses serious concern. Herein, an organic–inorganic hybrid material, polypyrrole (PPY)-modified Mg...

Synthesis of Polypyrrole-Modified Layered Double Hydroxides for EfficientRemoval of Cr(VI)

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Removal of hexavalent chromium Cr (VI) using activated carbon prepared from mango kernel activated with H3PO4

Microporous activated carbon was prepared from almond shell powder and activated with H3PO4 and was used for the removal of Cr (VI). The characterization of activated carbon was done for Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer– Emmett–Teller (BET) surface area measurement and elemental analysis. The batch experiments were conducted to study the effects of contact time, solution pH, adsorbent dose, initial chromium concentration and temperature on removal of Cr (VI). The Cr (VI) removal was found to be 100% at an initial pH of 2. The equilibrium data for the adsorption of Cr (VI) on the adsorbent were fitted with Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherm models. The Langmuir isotherm model fitted better and values of model parameters qm, b, R 2 and RL were found to be 195, 0.024, 0.98 and 0.45, respectively. Adsorption kinetics was analyzed for the pseudo first order, pseudo second order and intra-particle diffusion situations. Thermodynamic parameters revealed the spontaneous, endothermic and increased randomness nature of the adsorption process. The values of Δ H and Δ S were found to be 22.9 KJ/mol and 95.3 J/mol-K. doi: 10.2166/aqua.2018.047 om http://iwaponline.com/aqua/article-pdf/67/8/724/519027/jws0670724.pdf er 2021 M. K. Rai B. S. Giri (corresponding author) Y. Nath H. Bajaj S. Soni R. S. Singh B. N. Rai Department of Chemical Engineering & Technology, IIT (BHU), Varanasi, 221005, U.P., India E-mail: balendushekher23@gmail.com R. P. Singh Department of Municipal Engineering, Southeast University, Nanjing 210096, China

M. K. Rai

Papers

Removal of hexavalent chromium Cr (VI) using activated carbon prepared from mango kernel activated with H3PO4

Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from almond shell: kinetics, equilibrium and thermodynamics study

Efficient removal of Cr (VI) from aqueous solution by using tannery by-product (Buffing Dust).