Equbal A. Khan

Adsorptive removal of rhodamine B from textile wastewater using water chestnut (Trapa natans L.) peel: adsorption dynamics and kinetic studies

Water chestnut peel, an agricultural bio-waste, was used as a biosorbent for removal of rhodamine B (RhB), basic textile dye, from an aqueous solution. The effects of various experimental parameters were studied. The equilibrium data correlated well with a Freundlich isotherm (R2 = 0.98–0.99) followed by a Halsey isotherm model (R2 = 0.98–0.99) which indicated heterogeneity of the adsorbent surface and multilayer adsorption of RhB dye onto the water chestnut peel waste (WCPW). High correlation coefficients (R2 = 0.99) together with close agreement between experimental qe (0.4–1.7 mg g−1) and calculated qe (0.4–2.5 mg g−1) suggested that the adsorption process followed pseudo-second-order kinetics, with k2 values in the range of 52–3.4 × 10−1 g mg−1 min−1 at different concentrations. The overall mechanism of adsorption was controlled by both liquid-film and intra-particle diffusions. The negative values of change in Gibbs free energy (−ΔG0 = 19.2–29.2 kJ mol−1) and positive values of change in enthalpy (ΔH0 = 30.9–117.6 kJ mol−1) revealed the process to be spontaneous and endothermic. WCPW was found to be an effective adsorbent for removal of RhB, a cationic dye, from an aqueous solution.

Removal of malachite green from aqueous solution using waste pea shells as low-cost adsorbent – adsorption isotherms and dynamics

The adsorptive removal of malachite green (MG) from aqueous solution using waste pea shells (Pisum sativum L.) is reported. Optimized conditions for maximum uptake were established. The adsorption was best described by the Freundlich model. A pseudo-second-order kinetic model correlated best with the data. Liquid-film and intra-particle diffusion control the overall process. Thermodynamic parameters indicated that adsorption was spontaneous, endothermic, and accompanied with an increase in entropy. Low contact time and high removal efficiency at natural pH of water recommend pea shells as efficient low-cost adsorbent for removal of MG from wastewaters.

Removal of congo red and basic violet 1 by chir pine (Pinus roxburghii) sawdust, a saw mill waste: batch and column studies

The efficiency of chir pine sawdust (CPS) for adsorptive removal of the dyes, congo red (CR) and basic violet 1 (BV), from aqueous solution was evaluated using batch and column studies. The equilibrium was attained in 60 min for CR and 45 min for BV. The adsorption of BV obeyed the Langmuir isotherm model while the Freundlich isotherm fitted the equilibrium data of CR adsorption. The Langmuir monolayer adsorption capacities (Qo) of CPS for BV and CR were 11.3 and 5.8 g kg−1, respectively. The kinetic data for CR were best fitted to the Lagergren pseudo-first-order model and for BV to the pseudo-second-order model. The intra-particle diffusion was found to be the rate-controlling step for CR adsorption, while the adsorption kinetics of BV were controlled by both intra-particle and liquid-film diffusion. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The adsorption activation energy (Ea) for CR (124 kJ mol−1) implied chemical adsorption while that for BV (5.4 kJ mol−1) indicated physical adsorption. An increase in the Thomas model constant (KTh) with increasing flow indicated that for both dyes the mass transport resistance decreased during adsorption. Thus, CPS may be an efficient low-cost adsorbent for decolorization of dye-containing wastewaters.

Uptake of Cu2+ and Zn2+ from simulated wastewater using muskmelon peel biochar: Isotherm and kinetic studies

Abstract The muskmelon peel, an abundant common food waste material, has been gainfully utilized for the production of biochar. The biosorptive characteristics of muskmelon peel biochar towards copper(II) and zinc(II) from water are investigated. The biochar is characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) studies. The various process parameters for the removal of copper(II) and zinc(II) using biochar are optimized. The maximum biosorption of Cu(II) and Zn(II) is attained at pH 7. Maximum Langmuir adsorption capacity (qm) are 78.74 for copper(II) and 72.99 mg/g for zinc(II) at 303 K. Langmuir isotherm is found to best fit the equilibrium data indicating homogeneous adsorption of metal ions onto the biochar surface. The pseudo-second order kinetic model describes the data best indicating adsorption of one molecule of metal ions onto two surface sites. Thermodynamic parameters suggest the adsorption process to be spontaneous and exothermic. Both liquid-film and intra-particle diffusions controll the overall kinetics of the adsorption process. Biochar proved to be an inexpensive and efficient adsorbent for the removal of titled metals from liquid phase.