Microporous carbon with highly dispersed nano-lanthanum oxide (La2O3) for enhanced adsorption of methylene blue

Abstract

• Nano La 2 O 3 is ideal to induce extra microporosity on carbon granules by heat treatment at 873 K. • Resulted carbon retained their inherent honey comb structures where nucleated metal oxide are occupied on the edges. • Material is ideal to scavenge cationic dyes by electrostatic activation because of O 2− ions of these occupied nano La 2 O 3 with organics. • John-Sivanandan Achari isotherms of GACLaO873 has three phases identified as due to molecular sieve effects, donor–acceptor and electrostatic attraction type adsorptions in the liquid phase. Activated carbon doped with Lanthanum compounds are prepared and used as a preferred material for adsorption treatment systems. In this study, use of nano La 2 O 3 and La 3+ is attempted as tuning agents for granular activated carbons (GAC) and products are marked as GACLaX and GACLaOX series, produced under controlled activation (473–1273 K) for a Lanthanum/carbon ratio 0.04. They were tested for their physico-chemical features, textural superiority, and efficiency determined by XRD, FTIR, SEM, XPS, Raman, and N 2 /BET and t-plots. It is found that carbon GACLaO873 (GAC activated with nano lanthanum oxide at 873 K) has good microporosity and adsorption efficiency. Nano La 2 O 3 and La 3+ incorporated extra microporosity ( SA micro ) measured as 707 m 2 /g for GACLaO873 compared to native carbon GAC (589 m 2 /g). The respective surface area ( SA BET ) of these new carbons are determined as 946 m 2 /g (GACLaO873), 953 m 2 /g (GACLa1073), and 997 m 2 /g (GAC383). Suitability of the new carbon materials in solid–liquid batch reactor systems is studied for methylene blue (MB) in concentration ranges 25–1500 mg/L. Analysis of equilibrium isotherm uptake data by John-Sivanandan Achari isotherm model found distinct features of different adsorption phases (kinks) in their plots. For GACLaO873, monolayer coverage q m (J-SA) has been 256 mg/g against the basic carbon GAC383 (190 mg/g). Lanthanum activated carbon GACLa1073 has been noted with adsorption efficiency for metal ions, Mn (99.3%), Fe (99.1%), Co (96.6%), As (76.3%), Ba (63.0%), Li (50.4%), Al (71.3%), Cr (47.7%), Ni (99.2%), Cu (7.11%), Zn (24.3%), Cd (55.1%), Tl (32.6%) and Pd (94.9%) tested for a contaminated groundwater sample as a field trial. Lanthanum, La 3+ , and nano La 2 O 3 doped activated carbon series (GACLaX and GACLaOX) prepared under a controlled condition and activation temperature X, bears good microporosity and adsorption efficiency for organic and metal ion contaminants.