Meng-Wei Wan

Adsorption of indium(III) ions from aqueous solution using chitosan-coated bentonite beads

Batch adsorption study was utilized in evaluating the potential suitability of chitosan-coated bentonite (CCB) as an adsorbent in the removal of indium ions from aqueous solution. The percentage (%) removal and adsorption capacity of indium(III) were examined as a function of solution pH, initial concentration, adsorbent dosage and temperature. The experimental data were fitted with several isotherm models, where the equilibrium data was best described by Langmuir isotherm. The mean energy (E) value was found in the range of 1-8kJ/mol, indicating that the governing type of adsorption of indium(III) onto CCB is essentially physical. Thermodynamic parameters, including Gibbs free energy, enthalpy, and entropy indicated that the indium(III) ions adsorption onto CCB was feasible, spontaneous and endothermic in the temperature range of 278-318K. The kinetics was evaluated utilizing the pseudo-first order and pseudo-second order model. The adsorption kinetics of indium(III) best fits the pseudo-second order (R(2)>0.99), which implies that chemical sorption as the rate-limiting step.

Removal of oxidized sulfur compounds using different types of activated carbon, aluminum oxide, and chitosan-coated bentonite

AbstractThe adsorption of benzothiophene sulfone and dibenzothiophene sulfone from diesel using six different types of adsorbents were investigated. Adsorbents used were commercial adsorbents granular-activated carbon (GAC), aluminum oxide (ALU), novel adsorbents chitosan-coated bentonite (CHB), and metal-ion impregnated activated carbons, where there types of metal ions, Cu2+, Fe3+, and Ni2+, were loaded (Cu2+/AC, Fe3+/AC, Ni2+/AC). Kinetic studies conducted showed that the adsorption process followed a pseudo-second-order kinetics. Equilibrium studies indicated that the heterogeneous and homogenous monolayer adsorption and are present in the process. Moreover, based on the results of sulfone removal using the synthetic diesel fuel, increasing removal efficiencies of Benzothiophene sulfone followed the order of ALU < GAC < Cu2+/AC <  < Fe3+/AC < CHB, while for dibenzothiophene sulfone (DBTO) removal, increasing DBTO removed efficiencies followed the order of GAC < CHB < ALU < Cu2+/AC ≈ Fe3+/AC ≈ Ni2+/AC.

Competitive Fixed-Bed Adsorption of Pb(II), Cu(II), and Ni(II) from Aqueous Solution Using Chitosan-Coated Bentonite

Fixed-bed adsorption studies using chitosan-coated bentonite (CCB) as adsorbent media were investigated for the simultaneous adsorption of Pb(II), Cu(II), and Ni(II) from a multimetal system. The effects of operational parameters such as bed height, flow rate, and initial concentration on the length of mass transfer zone, breakthrough time, exhaustion time, and adsorption capacity at breakthrough were evaluated. With increasing bed height and decreasing flow rate and initial concentration, the breakthrough and exhaustion time were observed to favorably increase. Moreover, the adsorption capacity at breakthrough was observed to increase with decreasing initial concentration and flow rate and increasing bed height. The maximum adsorption capacity at breakthrough of 13.49 mg/g for Pb(II), 12.14 mg/g for Cu(II), and 10.29 mg/g for Ni(II) was attained at an initial influent concentration of 200 mg/L, bed height of 2.0 cm, and flow rate of 0.4 mL/min. Adsorption data were fitted with Adams-Bohart, Thomas, and Yoon-Nelson models. Experimental breakthrough curves were observed to be in good agreement ( and ) with the predicted curves generated by the kinetic models. This study demonstrates the effectiveness of CCB in the removal of Pb(II), Cu(II), and Ni(II) from a ternary metal solution.

Adsorption of Copper (II) by Chitosan Immobilized on Sand

Because of the dramatic develop of industry, heavy metal pollution has become a global environmental considerations. The heavy metals in the soil and groundwater have endangered our environment and human body by direct or indirect pathway. Thus, how to solve efficiently the heavy metal pollution in groundwater has become the most essential issue around the world. Theoretically, the traditional remediation method is physicalchemical processes, which resulted in high capital cost and serious damage in contaminated sites. Currently, bioremediation is a developing biologic process that offers the possibility to destroy or render harmless various contaminants using natural biological activity. As such, it uses relatively low-cost, low-technology techniques, which generally have a high public acceptance and can often be carried out on site. Biopolymer is a biodegradable material, and becomes a newly developing tendency for many industries. Those materials can be degraded by landfill process, which provides the nutrient for microorganisms, plants and animals. Based on this concept, obtaining form insects, the shell of aquatic crustaceans (crab and shrimp), and the cell wall of fungus. Chitin and Chitosan have widely applied in the adsorption study of heavy metal based on their chemical structures, reaction characteristics and modification properties. This research is based on the ideal of green design and using biodegradable material (chitosan) coated with sand. Nature materials such as sand, soil, clay and chitosan used as adsorbent to examine by Cu(superscript 2+) adsorption capability and isotherms analysis using Langmuir isotherm. In the considerations of real scale and cost-effective applications, sand was immobilization on chitosan to uptake the Cu(superscript 2+) ions in aqueous solution. Moreover, the adsorption capacity of 5% chitosan-coated sand (10.87 mg/g) was a better adsorbent compared to chitosan used alone (7.55 mg/g), 1% (3.38 mg/g) and 2.5% (4.50 mg/g) weight percentages coasted with chitosan. It is suggested that using 5 % chitosan-coated sand as a bioadsorbent in wastewater treatment process.

Feasibility studies on arsenic removal from aqueous solutions by electrodialysis

The effectiveness of electrodialysis (ED) in removing inorganic arsenic (As) from aqueous solution was investigated. A tailor-made ED stack was used to perform current-voltage and optimization experiments in a recirculating batch mode. Samples were pre-oxidized with NaClO using 1:2 sample to oxidant weight ratio (RS:O) to transform 100% of As(III) to As(V) in 180 seconds. A high feed water conductivity of 1500 μS/cm and a low feed water conductivity of 800μS/cm had limiting currents of 595 mA and 525 mA, respectively. Optimum experimental conditions that provided maximum As separation were applied potential (E) of 12 V, feed flow rate (Q) of 0.033 L/s, feed concentration (C) of 662.0 μg L−1, and operating time (t) of 45 min, the most significant ones were applied potential, feed concentration and operating time. Model confirmation experiments showed a good agreement with experimental results with only 0.031% error. The total As in the diluate stream was 4.0 μg L−1, consisting of an average of 3.0 μg L−1 As(V) and 1.0 μg L−1 As(III).

Ultrasound irradiation combined with hydraulic cleaning on fouled polyethersulfone and polyvinylidene fluoride membranes

In this study, an ultrasonic irradiation technique was utilized to mitigate the fouling of polyethersulfone (PES) and polyvinylidene fluoride (PVDF) membranes. The use of ultrasound at 20 kHz was applied to a dead-end microfiltration cell in order to mitigate fouling caused by the presence of colloidal bentonite particles. The effect of ultrasonic power and pulse duration on the permeate flux recovery was examined. Measurements indicate that an increase in ultrasonic power and longer pulse duration results to a higher permeate flux recovery. In order to reduce power consumption, a low to high power shift (LHPS) and pulsation method, were investigated. Methods of cleaning such as ultrasonic irradiation, ultrasonic cleaning with forward flushing and ultrasonic cleaning with backwashing were utilized and their cleaning efficiencies were examined. The cleaning performance was assessed using the clean water flux method and scanning electron microscope analysis of the cleaned membranes. Results showed that LHPS and pulsation method both improve the permeate flux recovery but were not able to attain the 93.97 and 74.88% flux recovery for PES and PVDF that was achieved by constant-15 W ultrasonic cleaning. In addition, forward flushing and backwashing may enhance the performance of ultrasonic cleaning at 9 W but could become disadvantageous at 15 W.

Fouling Elimination of PTFE Membrane under Precoagulation Process Combined with Ultrasound Irradiation

Precoagulation is one of the effective pretreatments in membrane filtration. This process mitigates membrane fouling, which is the major drawback of membrane technology in drinking water and wastewater treatment. This study investigated the effects of precoagulation under different coagulation mechanisms on membrane fouling. Use of ultrasound in polytetrafluoroethylene (PTFE) membrane cleaning was also evaluated. In precoagulation, synthetic raw water was precoagulated using aluminum sulfate at different coagulation mechanisms, named electrostatic patch effect (EPE), charge neutralization (CN), and sweep flocculation (SW). Flocs produced from different coagulation mech- anisms exhibited different sizes, structures, and strengths. Likewise, the fouling type generated from each mechanism was demonstrated as pore blocking for EPE, cake formation for SW, and combination phenomenon for CN. Moreover, this study indicated that the membrane flux was enhanced in the sequence of EPE > CN > SW. The flux recovery rate after ultrasonic cleaning was in the sequence of SW > CN > EPE. Finally, this study evidenced that the floc characteristics from various coagulation mechanisms affected membrane per- formance, fouling types, and ultrasonic cleaning efficiency. DOI: 10.1061/(ASCE)EE.1943-7870.0000406.

Removal of manganese ions from synthetic groundwater by oxidation using KMnO4 and the characterization of produced MnO2 particles

The aim of this study is to investigate the conditions for the removal of manganese ions from synthetic groundwater by oxidation using KMnO(4) to keep the concentration below the allowed level (0.05 mg/L). The process includes low-level aeration and addition of KMnO(4) in a Jar test system with Mn(2 + ) concentration of 0.50 mg/L, similar to that of natural groundwater in Taiwan. Different parameters such us aeration-pH, oxidant dose, and stirring speed were studied. Aeration alone was not sufficient to remove Mn(2 + ) ions completely even when the pH was increased. When a stoichiometric amount of KMnO(4) (0.96 mg/L) was used, a complete Mn(2 + ) removal was achieved within 15 min at an optimum pH of 8.0. As the amount of KMnO(4) was doubled, lower removal efficiency was obtained because the oxidant also generated manganese ions. The removal of Mn(2 + ) ions could be completed at pH 9.0 using an oxidant dose of 0.48 mg/L because Mn(2 + ) could be sorbed onto the MnO(2) particles. Finally, The MnO(2) particles were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Effect of coagulation mechanisms on the fouling and ultrasonic cleaning of PTFE membrane.

In this study, the effect of coagulation pretreatment on membrane fouling and ultrasonic cleaning efficiency was investigated using a dead-end polytetrafluoroethylene (PTFE) microfiltration system. The extent of membrane fouling was examined under different coagulation mechanisms such as charge neutralization (CN), electrostatic patch effect (EPE) and sweep flocculation (SW). Fouling through EPE mechanism provided the greatest flux decline and least permeate flux recovery over CN and SW. EPE produces more stable, smaller and more compact flocs while CN and SW have large, easily degraded and highly-branched structured flocs. The predominant fouling mechanism of EPE, CN and SW is pore blocking, a combination of pore blocking and cake formation, and cake formation, respectively. Better permeate flux recovery is observed with SW over CN and EPE, which implies formation of less dense and more porous cake deposits. The morphology of fouled membranes was examined using scanning electron microscopy (SEM).

Arsenate removal from aqueous solution using chitosan-coated bentonite, chitosan-coated kaolinite and chitosan-coated sand: parametric, isotherm and thermodynamic studies

In the present work, the removal efficiency of As(V) from aqueous solution using chitosan-coated bentonite (CCB), chitosan-coated kaolinite (CCK) and chitosan-coated sand (CCS) was evaluated. The chitosan-based adsorbents were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, the Brunauer-Emmett-Teller method and thermogravimetric analysis. Kinetic studies revealed that As(V) uptake using CCB, CCK and CCS fitted well with the pseudo-second order equation (R2 ≥ 0.9847; RMSE ≤ 9.1833). Equilibrium data show good correlation with the Langmuir model (R2 ≥ 0.9753; RMSE ≤ 8.5123; SSE ≤ 16.2651) for all adsorbents, which implies monolayer coverage onto homogenous energy sites. The Langmuir adsorption capacity for As(V) at pH 7.0 was determined to be 67.11, 64.85, and 16.78 mg/g for CCB, CCK and CCS, respectively. Thermodynamic studies show that As(V) uptake is exothermic in nature using CCK and endothermic using CCB and CCS. Moreover, adsorption of As(V) was feasible and spontaneous for CCB and CCS at 298 to 328 K. Results show that CCB is the most effective adsorbent in the removal of As(V) from water due to its high surface area and large pore diameter.