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This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity (q max ) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-secondorder kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (∆H°, ∆S° and ∆G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy (E) and activation energy (E a ) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

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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.

Copper is an essential element for living but imbalance between Cu + and Cu 2+ produces free radicals. Quercetin is an effective metal chelator and its chelates are often better free radical scavengers than free quercetin. In this study, the syntheses, characterizations, antioxidant activities of quercetin as well as its Cu (I) and Cu (II) complexes using UV-VIS, IR spectrometric methods, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay were investigated. 1:1 and 2:1 stoichiometric ratios were obtained for the dark-brown Cu + and green Cu 2+ quercetin complexes respectively. Bathochromic shifts from 268 nm (band II) and 362 nm (band I) in quercetin were observed at 302 nm and 386 nm for Cu (I)-quercetin complex and at 281 nm and 394 nm for Cu (II)-quercetin complex. FT-IR showed shifts in the positions of carbonyl and hydroxyl groups with presence of bands at 932.01 cm-1 in Cu (I)-quercetin and 928.57 cm-1 in Cu (II)-quercetin confirming complexation. Both complexes were better free radical scavengers than free quercetin with Cu (I)-quercetin complex having the highest antioxidant activity. Higher antioxidant activity and differences in spectra characters of Cu (I)-quercetin complex are related to relative stability of fully filled orbital of Cu + over Cu 2+ .