Optical detection and efficient removal of transition metal ions from water using poly(hydroxamic acid) ligand

[Display omitted] The green colour Cu-Ligand complex is shown in figure inset after adsorption of copper ion. The reflectance spectra were increased when increasing of Cu2+ ion concentration from 0 to 15ppm. A broad peak at 673nm was created when Cu2+ ion is adsorbed by ligand whereas blank polymeric ligand does not shows any peak at 673nm. •Optical color signals achieving for metal ion complexation.•Excellent adsorption properties with some transition metal ions were observed.•Reusability for 12 cycles shows without any significant loss of its removal performances.•This new type adsorbent can be used for metal ions removal from wastewater. A copolymer, cellulose-graft-poly(methyl acrylate), was synthesized by a free-radical initiating process, and the ester functional groups converted into the hydroxamic acid ligand. The pH of the solution acts as a key factor in achieving optical color signals of metal-complexation. The reflectance spectra of the [M-ligand]n+ complex was found to be at the highest absorbance, ranging from 92 to 99% at pH 6, with absorbance noted to increase as metal ion concentrations were increased. A broad peak at 673nm for Cu2+ was observed, indicating the presence of the charge transfer (π–π transition) complex. The developed ligand demonstrated superior adsorption capacity for copper (305.3mgg−1), as well as strong adsorption capacity for other metals; the adsorption capacities for Fe3+, Mn2+, Co2+, Cr3+, Ni2+, and Zn2+ were 275.6, 258.5, 256.6, 254.3, 198.5, and 190.1mgg−1, respectively. The experimental data of the adsorption kinetics of the metal ions fitted well with a pseudo-second-order rate equation. The obtained data demonstrated that the observed metal ion sorption was well fitted with the Langmuir isotherm model (R2>0.99), suggesting that the surface of the adsorbent is homogenous and monolayer. The reusability of the ligand was verified using the sorption/desorption process, demonstrating that the developed adsorbent can be reused for 12 cycles without significant loss of its original sensing and removal performance.