Kinetic and isotherm studies for lead adsorption from aqueous phase on carbon coated monolith

Adsorption of lead [Pb(II)] ions on two different types of carbon coated monoliths (CCM 600 and CCM 8000) was investigated with variations in the parameters such as agitation speed, pH, contact time, and Pb(II) initial concentration. Optimum Pb(II) adsorption was observed at pH: 5. The observed equilibration time on CCM 600 and CCM 8000 was 470 min and 350 min, respectively while, the equilibrium adsorption capacities were 14.2 mg/g and 15.2 mg/g at 50 mg/L initial Pb(II) concentration. The adsorption capacities on CCM 600 and CCM 8000 increased to 48 mg/g and 53.5 mg/g at 250 mg/L initial Pb(II) concentration. Linear and non-linear isotherm studies showed that equilibrium data better fitted to Freundlich isotherm model. Kinetic studies showed better applicability of pseudo-second order kinetics model. It was concluded that CCM 8000 showed better performance for Pb(II) ions removal compared to CCM 600

Adsorption of nickel on electric arc furnace slag: batch and column studies

The ability of electric arc furnace slag (EAFS), a by-product of the steel industry to adsorb nickel [Ni(II)] from an aqueous solution, was investigated by both batch and column operations. The characterization studies showed the mesoporous nature of EAFS with dominance of acidic sites. The adsorption was found to be dependent on the adsorbent dosage, contact time, the pH, and initial metal ion concentration. Optimum Ni(II) uptake was 160.92 mg/g at 1000 mg/L initial concentration with equilibration time 216 h. Adsorption follows the pseudo-second-order kinetics model. Linear and non-linear isotherm models revealed the applicability of the Langmuir model confirming monolayer adsorption. Both the column bed capacity and the exhaustion time increased with increase in bed height. The saturation time was found to increase from 42 to 46 h with a decrease in the flow rate from 15 to 5 mL/min. The bed depth saturation time and Thomas models were evaluated. The experimental breakthrough curves agreed well with the predicted model

Optimization of bromate adsorption onto Fe-CNTs nanocomposite using response surface methodology

This study was aimed at employing response surface methodology (RSM) for optimization of process variables and identifying optimal conditions for the adsorption of bromate (BrO3-) from contaminated water using multi-walled carbon nanotubes, based on iron hydr(oxide), Fe-CNTs nanocomposite. Fifteen experimental runs were conducted in batch mode to study the effect of individual as well as interactive process variables,  i.e., pH, BrO3− initial concentration, and adsorbent dose, on the removal of BrO3− using Box–Behnken design (BBD) of RSM. The coefficient of determination (R2) at 98.34% indicated a good agreement between actual and predicted values. The main effect and contour plot were drawn to obtain the independent and interactive effect of operational variables on BrO3− uptake. A process optimization curve was drawn to determine the optimum operating conditions that lead to a desirable response. The optimum conditions for BrO3− adsorption using Fe-CNTs nanocomposite were found to be pH 2.0, initial BrO3− concentration of 10.0 mg/L, and adsorbent dose of 0.010 g per 50 mL solution

Acid modified carbon coated monolith for methyl orange adsorption

Carbon coated monolith (CCM) was chemically modified by treating with nitric acid. The acid modified carbon coated monolith (ACCM) was then characterized by using various techniques. Two folds increase in acidic sites was observed on ACCM compared to CCM. Surface studies showed mesoporous nature of ACCM. A decrease in ACCM surface area and an increase in pore volume observed after the modification. The ATR-FT-IR studies showed increase in carboxylic groups on ACCM confirming CCM oxidation by nitric acid. The pH studies showed optimum adsorption (88 mg/g) at pH 6 which is very near to pHPZC of ACCM. Contact time studies showed equilibration time in between 4320 and 4560 min for initial MO concentration range 0.05–0.6 g/L. Comparatively 53% higher MO adsorption was observed on ACCM than CCM under similar experimental conditions. Freundlich model applicability confirms multilayer MO adsorption on ACCM surface. Pseudo-second-order kinetics model was fitted best to the experimental data revealing chemical nature of adsorption process. The adsorption process is endothermic and spontaneous in nature. Desorption studies showed optimum MO recovery (73%) when 1 N NaOH was used as an eluent

Biosorption and desorption of nickel on oil cake: batch and column studies

Biosorption potential of mustard oil cake (MOC) for Ni(II) from aqueous medium was studied. Spectroscopic studies showed possible involvement of acidic (hydroxyl, carbonyl and carboxyl) groups in biosorption. Optimum biosorption was observed at pH 8. Contact time, reaction temperature, biosorbent dose and adsorbate concentration showed significant influence. Linear and non-linear isotherms comparison suggests applicability of Temkin model at 303 and 313 K and Freundlich model at 323 K. Kinetics studies revealed applicability of Pseudo-second-order model. The process was endothermic and spontaneous. Freundlich constant (n) and activation energy (Ea) values confirm physical nature of the process. The breakthrough and exhaustive capacities for 5 mg/L initial Ni(II) concentration were 0.25 and 4.5 mg/g, while for 10 mg/L initial Ni(II) concentration were 4.5 and 9.5 mg/g, respectively. Batch desorption studies showed maximum Ni(II) recovery in acidic medium. Regeneration studies by batch and column process confirmed reutilization of biomass without appreciable loss in biosorption

Carbon coated monolith, a mesoporous material for the removal of methyl orange from aqueous phase: adsorption and desorption studies

The cordierite monolith was successfully modified to carbonaceous material termed as carbon coated monolith (CCM). Surface studies showed about 65% of the total pore volume falls in mesopore range with acidic functionality dominating over the surface. Batch adsorption experiments were carried out to study the applicability of CCM for the removal of methyl orange (MO) from aqueous solution. Different parameters such as effect of MO concentration, contact time, initial pH, regeneration and desorption potential of CCM were studied. Optimum adsorption of MO on CCM was observed at pH 6 (27.2 mg/g). The increase in initial MO concentration from 50 to 500 mg/L leads to increase in adsorption capacity from 15.99 to 88.5 mg/g. The observed equilibration time ranged in between 5000 and 5800 min. Linear and non-linear isotherm studies showed better applicability of Freundlich model. Kinetics studies showed better fitting for pseudo-second-order model. The Weber and Morris model showed multi-linearity indicating two or more steps were involved to describe the adsorption process. Desorption studies showed maximum recovery of MO when alkaline NaOH solution was used as an eluent. The regeneration studies showed decrease in adsorption capacity from 47.93 to 23.76 mg/g after three cycles

Bioremediation and Electricity Generation by Using Open and Closed Sediment Microbial Fuel Cells

The industrial contamination of marine sediments with mercury, silver, and zinc in Penang, Malaysia was studied with bio-remediation coupled with power generation using membrane less open (aerated) and closed (non-aerated) sediment microbial fuel cells (SMFCs). The prototype for this SMFC is very similar to a natural aquatic environment because it is not stimulated externally and an oxygen sparger is inserted in the cathode chamber to create the aerobic environment in the open SMFC and no oxygen supplied in the closed SMFC. The open and closed SMFCs were showed the maximum voltage generation 300.5 mV (77.75 mW/m2) and 202.7 mV (45.04 (mW/m2), respectively. The cyclic voltammetry showed the oxidation peak in open SMFCs at +1.9 μA and reduction peak at -0.3 μA but in closed SMFCs oxidation and reduction peaks were noted at +1.5 μA and -1.0 μA, respectively. The overall impedance (anode, cathode and solution) of closed SMFCs was higher than open SMFCs. The charge transfer impedance showed that the rates of substrate oxidation and reduction were very low in the closed SMFCs than open SMFCs. The Nyquist arc indicated that O2 act as electron acceptor in the open SMFCs and CO2 in the closed SMFCs. The highest remediation efficiency of toxic metals [Hg (II) ions, Zn (II) ions, and Ag (I) ions] in the open SMFCs were 95.03%, 86.69%, and 83.65% in closed SMFCs were 69.53%, 66.57%, and 65.33%, respectively, observed during 60–80 days. The scanning electron microscope and 16S rRNA analysis showed diverse exoelectrogenic community in the open SMFCs and closed SMFCs. The results demonstrated that open SMFCs could be employed for the power generation and bioremediation of pollutants

β-carotene adsorption onto mesoporous carbon-coated monolith column: dynamic studies

β-carotene adsorption dynamics from isopropyl alcohol (IPA) solution onto a mesoporous carbon-coated monolith (MCCM) column was studied. Kinetics and mass transfer parameters were modeled. Thomas and Adams-Bohart models were applied to the experimental data obtained from dynamic studies. The effects of bed depth, flow rate, and influent concentration on breakthrough curves and adsorption capacity were investigated. The results showed that β-carotene equilibrium uptake increased with decreasing flow rate and increasing influent concentration. The optimum adsorption capacity (1.37 mg/g) was achieved at 20 mg/L initial β-carotene concentration, 47.5 cm bed height, and 1.0 mL/min flow rate. The time to attain breakthrough point decreased, while a sharp breakthrough curve was observed with increase in flow rate and influent concentration and a decrease in bed height

Desorption of β-carotene from mesoporous carbon coated monolith: isotherm, kinetics and regeneration studies

β-carotene, a natural antioxidant, beneficial form human health prospective. In this study we had examined the recovery of β-carotene form mesoporous carbon coated monolith (MCCM) by batch process. Desorption kinetics and isotherm studies were carried out by using n-hexane as an eluent. Isotherm studies showed better applicability of Langmuir model. The first-order two-compartment three-parameter kinetics model as a function of initial loading concentration and reaction temperature was applied. It was observed that β-carotene desorption process is controlled by both rapid and slow desorption. Results showed that the slow desorption fraction increases from 0.8446 to 0.9007 with increase in initial loading concentration from 10.83 to 39.72 mg/g while, the slow desorption fraction decreases from 0.9261 to 0.8684 with increase in reaction temperature form 30 to 50°C. The activation energies for rapid and slow desorption were 7.88 and 44.47 kJ/mol, respectively. The regeneration studies were carried out by both chemical and thermal process. The regeneration efficiency (RE%) for the three consecutive cycles reduced from 96.24 to 60.04% and 94.51 to 81.62% for chemical and thermal regeneration processes, respectively

Fabrication of mesoporous carbons coated monolith via evaporative induced self-assembly approach: effect of solvent and acid concentration on pore architecture

Carbon coating onto monolith through soft-template approach have been accomplished by means of evaporative induced self-assembly (EISA). Variation in acid and alcohol content on monolith's surface properties was studied, while β-carotene was used as a modelled adsorbate. The pore architecture of adsorbent samples was analysed through corresponding surface chemistry, N2 sorption isotherm, pore size distribution (PSD) plot, Brunauer–Emmett–Teller (BET), Barett–Joyner–Halenda (BJH) model and scanning electron microscopy (SEM). SEM images displayed a well-covered interconnected worm-like framework of carbonaceous materials over monolith surface. Surface chemistry studies revealed dominance of acid functionalities over adsorbent samples surface, while basic functionalities remain unaltered. Carbon loading increased with increase in acid concentration, while it decreased with increase in alcohol content. The adsorbent surface area decreased with increase in acid concentration and alcohol content. The β-carotene adsorption capacities on synthesized samples varied between 179.60 (optimum) and 112.56 mg/g (lower), respectively. Optimum β-carotene adsorption was observed on samples MC0.2 and MC5 with alcohol and acid content of 5 mL and 0.2 mL, respectively