Abstract
Macadamia nutshell powder oxidized by hydrogen peroxide solutions (MHP) was functionalized by immobilizing 1,5′-diphenylcarbazide (DPC) on its surface. The effectiveness of grafting was confirmed by the Fourier transform infrared spectrum due to the presence of NH and C=C stretches at 3361, 1591, and 1486 cm−1, respectively, on the grafted material which were absent in the nongrafted material. Thermogravimetric analysis revealed that the presence of DPC on the surface of Macadamia shells lowered the thermal stability from 300°C to about 180°C owing to the volatile nature of DPC. Surface roughness as a result of grafting was appreciated on the scanning electron microscopy images. Parameters influencing the adsorptive removal of Cr(VI) were examined and found to be optimal at pH 2, 120 min, 150 mg/L, and 2.5 g/L. Grafting MHP with DPC leads to an increase in the Langmuir monolayer capacity from 37.74 to 72.12 mg/g. Grafting MHP with DPC produced adsorbent with improved removal efficiency for Cr(VI).
Highlights
Natural biosorbents like mango kernels, Macadamia nutshells, coconut shells, pine cone, almond shells, sawdust, palm branches, and hazelnut consist in their plant cell walls the lignin, cellulose, and hemicellulose as the main structural components [1,2,3,4,5]
These materials contain a cornucopia of surface functional groups including ketones, aldehydes, esters, ethers, and alcohols. e escalating use of natural biosorbents in adsorption for the remediation of metal pollutants has been largely due to their abundant availability, inexpensiveness, biodegradability, easy desorption, good reusability, and the diverse functional groups they possess which are needed for metal abstraction [6,7,8]
Upon being used as adsorbents, there is a tendency of small organic molecules trapped within the polymeric cross-linked chains being released into the environments causing high biological oxygen demand and chemical oxygen demand [9]. ese drawbacks have restricted the utilization of biosorbents in adsorption in their pristine form
Summary
Natural biosorbents like mango kernels, Macadamia nutshells, coconut shells, pine cone, almond shells, sawdust, palm branches, and hazelnut consist in their plant cell walls the lignin, cellulose, and hemicellulose as the main structural components [1,2,3,4,5] These materials contain a cornucopia of surface functional groups including ketones, aldehydes, esters, ethers, and alcohols. Careless disposal and improper treatment of effluents from leather tanning, electroplating, textile dyeing, mining, and wood preservation industries lead to contamination of the environment by Cr(VI) compounds Owing to their advantages of simplicity, low cost, and fine-tuning of functional groups, adsorption methods have found more applications for the elimination of toxic metals. Adsorption was evaluated by varying pH, time, concentration, and dosage, and various models were used to substantiate the adsorption mechanism involved
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