Scavenging of hexavalent chromium from aqueous solution by Macadamia nutshell biomass modified with diethylenetriamine and maleic anhydride

Isothermal and Kinetics Modeling Approach for the Bioremediation of Potentially Toxic Trace Metal Ions Using a Novel Biosorbent Acalypha wilkesiana (Copperleaf) Leaves

The presence of trace metals in wastewater brings serious environmental pollution that threatens human health as well as the ecosystem throughout the world due to their non-biodegradability nature. The present study focuses on the bioremediation of toxic trace metals, namely arsenic (As), cadmium (Cd), and chromium (Cr), using Acalypha wilkesiana leaf raw biomass. The optimization of various process variables was done to determine the removal percentage of trace metal using Acalypha wilkesiana leaf raw biomass, and the optimum conditions were an adsorbent dose of 0.5 g, contact time 10 h, 8 h, and 10 h, process temperature 30 °C, initial concentration of trace metal as 30 µg/L, 30 mg//L, and 40 mg/L, and pH of 7.5, 7 and 7.5 for As5+, and Cd2+ and Cr6+, respectively. Acalypha wilkesiana leaf raw biomass is characterized using a scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transformation infrared spectroscopy (FTIR), zeta potential before and after adsorption of the trace metal ions. The study was well fitted for the equilibrium data for Langmuir isotherm for As5+, Cd2+, and Cr6+, Freundlich for As5+, Dubinin-Radushkevinch (D-R) for Cr6+, and Temkin for As5+ and Cr6+. The adsorption of all three trace metals was confirmed by the kinetics and thermodynamic studies to be following pseudo-second-order kinetics with endothermic as well as spontaneous processes, respectively. Thus, the present study indicates Acalypha wilkesiana leaf raw biomass as an effective and efficient novel biosorbent to remediate different trace metals from aqueous systems with its possible application in existing and novel methods for wastewater management.

Trends in removal of pharmaceuticals in contaminated water using waste coffee and tea-based materials with their derivatives

The introduction of large amounts of pharmaceuticals into the environmental waters is well-documented in literature with their occurrence reported in all different water matrices accessible to humans and animals. At the same time, the increasing consumption of coffee and tea-based beverages results in the generation of solid waste, which is mostly disposed-off in the environment. To minimize environmental pollution, coffee and tea-based materials have been proposed as suitable options to remove pharmaceuticals in environmental waters. Therefore, this article provides a critical review on the preparation and applications of coffee and tea-based materials in removing pharmaceuticals from contaminated water. In this context, most studies in literature focused on the applications of these materials as adsorbents, while only limited work on their role in degradation of pharmaceuticals is discussed. The successful application in adsorption studies is attributed to high surface areas of adsorbents and the ability to easily modify the adsorbent surfaces by incorporating functional groups that provide additional oxygen atoms, which promote easy interactions with pharmaceuticals. Hence, the adsorption mechanisms are mostly described by hydrogen bonding, electrostatic and π-π interactions with sample pH playing a dominant role in the adsorption process. Overall, the present article focused on the developments, trends and future research direction on the preparations and applications of coffee and tea-based materials for efficient removal of pharmaceuticals in water. PRACTITIONER POINTS: Review of tea and coffee wastes application for removal of pharmaceuticals in water Key applications in adsorption and degradation of pharmaceuticals in water Removal mostly explained by hydrogen bonding, electrostatic, and π-π interactions Trends, gaps, and future research to be explored are reviewed and highlighted.

Influence of pyrolysis temperature on biochar properties and Cr(VI) adsorption from water with groundnut shell biochars: Mechanistic approach

This study was envisaged to understand the effect of increasing pyrolysis temperature on the Cr(VI) removal potential of the groundnut shells derived biochars. The biochars were prepared at four different pyrolysis temperatures (350 °C, 450 °C, 550 °C, 650 °C) and were used unmodified to examine the adsorption potential for Cr(VI). Influence of biochar dose (1-10 g/L), pH_initial (2-10), Cr(VI)_initial (10-500 mg/L) on Cr(VI) adsorptions; adsorption kinetics and isotherms were investigated. The observations suggested that the pyrolysis temperature is the key player in deciding the physicochemical properties as well the adsorption potential of the biochars. SEM and FTIR analysis suggested significant morphological and functional transformations in biochars with increasing pyrolysis temperature. The pH_initial was found to be the most profound adsorption parameter determining the adsorption potential of the biochars. The Cr(VI) adsorption capacity of the biochars decreased with the increase of the pyrolysis temperature (142.87-31.25 mg/L) as well as the solution pH_initial. All the biochars attained 100% removal efficiency with 50 mg/L of Cr(VI)_initial and GNSB/350 achieved it in the minimum time (10 h) among all the biochars. GNSB/350 showed promising Langmuir adsorption capacity of 142.87 mg/L (pH 2, T_adsorption 30 °C, Cr(VI)_initial 10-500 mg/L). In addition, the adsorption mechanism was found to be a synergistic action of chemi/physi-sorption with monolayer adsorption. Hence, the pyrolysis temperature significantly altered the physicochemical properties of the biochars, which highly influenced the adsorption performance of biochars.