No abstract

This study reports useful application of biodegradable polymeric materials functionalized with silver nanoparticle (AgNPs) biosynthesized from cocoa pods as effective adsorbent for dye wastewater purification. Corn starch and hen feather were functionalized with AgNPs for adsorption of rhodamine B (Rh-B). All adsorbents were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. Decreased intensities of peaks, superior rougher cavities and smaller grain diameter of functionalized biomaterials affirmed the functionalization. Effects of pH, contact time, initial Rh-B concentrations and temperature were investigated and found to be significantly important. Four isotherm models were used to describe the adsorption process with Freundlich being the most suitable for all adsorbents indicating Rh-B adsorbed on heterogeneous multilayer surfaces of adsorbents. AgNPs modification greatly enhanced maximum monolayer adsorption capacities (q max) of feather (4.27-56.53 mg g −1) and starch (1.176-48.60 mg g −1) by 30-and 40-fold respectively. Kinetic rates of adsorption for starch best fitted Elovich, pseudo first order for feather whereas pseudo second order best suitable for starch-AgNPs and feather-AgNPs. Energies (3.89-7.68 kJ mol −1) of adsorption suggest that adsorption of Rh-B onto the adsorbents was by physiosorption. The negative values of ∆H° and ∆G° imply that adsorption processes were exothermic and spontaneous. Results in this study show that surface functionalization of starch and feather improved their adsorptive performances and will find valuable applications in dye remediation due to their biodegradability and cost-effectiveness.

No abstract

This study describes synthesis and characterization of corncob (CC), corncob nanocellulose (CCNC) and functionalized corncob (FCC) as unique adsorbents for methyl orange (MO) removal. Nanocellulose was synthesized via H 2 SO 4 hydrolysis and functionalization was achieved using H 3 PO 4 . All adsorbents were characterized by scanning electron microscopy coupled with energy dispersive X-ray and Fourier transform infra-red spectroscopy. Functionalization modified surface chemistry (disappearance of OH and appearance of PO 4 3− ), increased percentage carbon by 41.42% and produced welldeveloped pores. Nanocellulose retained intrinsic chemical properties of corncob though more porous with enhanced surface functionality prompted by more intense functional groups peaks and appearance of SO 4 2− . Maximum adsorption of MO occurred at pH 3.01, 4.11 and 2.09 for CC (54.34%), FCC (77.1%) and CCNC (96.81%) respectively. Adsorption parameters were fitted to four adsorption isotherms with Langmuir being the most appropriate to describe the adsorption process. Adsorption capacity increased from 17.86 mg g −1 in corncob to 60.82 mg g −1 in FCC and 206.67 mg g −1 in CCNC implying CCNC had the highest adsorption quality. The rate of adsorption was most accurately predicted by pseudo first order kinetics. Adsorption mechanism was governed by film diffusion with contribution from intra-particle diffusion. Adsorption process was spontaneous (− ∆G o ) at all temperatures (303-315 K), exothermic (− ∆H o ) and physical on CC (3.73 kJ mol −1 ) and CCNC (3.42 kJ mol −1 ) however it was endothermic (+ ∆H o ) and chemical on FCC (12.86 kJ mol −1 ). This study shows that CCNC is comparatively the best adsorbent with highest adsorption capacity.

The adsorption capacity of steam activated carbon prepared from Delonix regia pods SADRC for adsorption of Aniline Blue (AB) from aqueous solution was investigated under various experimental conditions. Batch study was conducted to assess the potential of the activated carbon for the removal of Aniline Blue from aqueous solution. Activated carbon prepared from Delonix regia pods was characterized using Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) Spectrophotometry before and after adsorption. The FTIR, spectra of SADRC pod before and after Aniline Blue adsorption were compared to study the impact of the Aniline Blue on the activated carbon developed from the Delonix regia pod. The stretching vibration band at 2169.54 cm −1 may be due to strong CN, while the stretching vibration band at around 1580-1650 cm −1 may be due to C=C stretching vibration. The bands around 1350 and 426.49 cm −1 are due to C-N and-SO 3 H group, respectively; this further suggests that some functional groups may be present on the surface of the carbon due to the low temperature of carbonization (300˚C) of the adsorbent. Equilibrium isotherm studies were carried out by varying the following four parameters: initial concentration of Aniline Blue dye solution, solution pH and adsorbent dose. The equilibrium data obtained were more fitted to Langmuir than Freundlich isotherm models. The correlation coefficient value (R 2) of the pseudo first order kinetics ranged from 0.08 to 0.85 while the R 2 of the pseudo second order kinetics ranged from 0.963 to 0.997 at all the temperatures and initial concentrations considered. This suggests that the adsorption kinetics of Aniline Blue onto SADRC can be * Corresponding author. S. A. Adebisi et al. 1222 represented with pseudo second order kinetic model. This study showed that Delonix regia pod could be effectively used as an adsorbent for the removal of Aniline Blue from aqueous solutions over a wide range of concentration and temperature.