Xuegang Luo

Effect of gelatinization and additives on morphology and thermal behavior of corn starch/PVA blend films

The blend films of ungelatinized and gelatinized starch/polyvinyl alcohol (PVA) were prepared with a solution casting method by the introduction of additives (glycerol/urea) or not. The phase morphologies and thermal behaviors of the blends were carefully analyzed. A droplet phase was observed in the blends containing ungelatinized starch and a laminated phase was observed in the blends containing gelatinized starch. For both ungelatinized and gelatinized starch/PVA blends, the melting temperature (T(m)) (210-230 °C) of PVA was detected, and the T(m) of gelatinized starch/PVA blends was higher than that of the ungelatinized starch/PVA blends. Blend films containing 16.8 wt% of glycerol or urea exhibited a decreased T(m). The introduction of additives (glycerol or urea) reduced the decomposition onset temperature of the blend films. These various morphologies and thermal behaviors could be attributed to the different hydrogen bonding interaction characteristics between starch and polyvinyl alcohol at different conditions.

Fixed-bed column study for Cu2+ removal from solution using expanding rice husk

This paper deals with removal of copper ions from solution by raw rice husk (RRH) and expanding rice husk (ERH). Different column design parameters like bed depth, flow rate and initial copper concentration were investigated. It was found that the equilibrium uptake (q(eq(exp))) of the ERH and RRH increased with increase in initial copper concentration but decreased with increase in flow rate and bed depth, respectively. The higher adsorption capacity and longer breakthrough time were observed for ERH in comparison with RRH, under the same conditions. Compared to coconut-shell activated carbon (C-AC), ERH was also found more effective in removing Cu(2+). 0.01 mol L(-1) HCl solution was used for desorption of column which was prior to absorb copper ion, and 0.01 mol L(-1) NaOH solution was used for re-activation. Column regeneration and reuse studies were conducted for adsorption-desorption cycle.

Adsorption of tannin from aqueous solution by deacetylated konjac glucomannan.

Konjac glucomannan treated by alkali solution through deacetylated reaction was used as a new water insoluble adsorbent to remove tannin from aqueous solution. A comprehensive study on adsorption of tannin by deacetylated konjac glucomannan (DKGM) was conducted regarding the effects of initial pH, adsorbent dosage, contact time, temperature and initial tannin concentration. The adsorption process was much dependent on the pH and temperature and was found to follow pseudo-second-order kinetics. The optimum pH value was at pH ranging from 2 to 6. The maximum removal efficiency of tannin from aqueous solution was 90%. Increasing the adsorption temperature would result in lower adsorption capacity, suggesting that adsorption of tannin onto DKGM was exothermic in nature. The adsorption isotherms were measured at various temperatures and correlated to Freundlich isotherms. Adsorption mechanism was confirmed that the interaction of DKGM and tannin was through hydrogen bonding. It was also observed that DKGM possesses excellent reusability for tannin removal.

Removal of copper and lead from aqueous solution by carboxylic acid functionalized deacetylated konjac glucomannan

Carboxylic acid functionalized deacetylated konjac glucomannan was synthesized by free radical graft copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) onto the backbone of deacetylated konjac glucomannan with subsequent chemical activation of the ester groups in the side chains of the resulting graft copolymer by sodium hydroxide. Effects of sodium hydroxide concentration and hydrolyzed time on the conversion of ester groups into carboxylic acid groups were studied. A comprehensive adsorption study of Cu(2+) and Pb(2+) ions from aqueous solution was also conducted regarding the effects of initial pH, adsorbent dosage, time, and initial concentration. The new konjac glucomannan adsorbent offered high removal efficiency, fast adsorption rate and high uptake capacity for Cu(2+) and Pb(2+) ions. The maximum removal efficiency at pH 5.0 was found to 98% for Cu(2+) and 99% for Pb(2+) ions. The kinetic data were fitted well to pseudo-second-order model. The maximum uptake capacity of Cu(2+) and Pb(2+) ions onto carboxylic acid functionalized deacetylated konjac glucomannan was found to 64.5 mg g(-1) and 191.3 mg g(-1), respectively. The isotherm adsorption data was well described by the Langmuir isotherm model.

New insights on degradation of methylene blue using thermocatalytic reactions catalyzed by low-temperature excitation

Although photocatalysis has been actively surveyed on removing organic pollutants in ultraviolet (UV) environment, because of lacking UV in solar exposure, photodegradation is difficult to be considerably degraded in conventional exposure condition. In this work, an innovative approach was proposed to compensate for it, which was developed in model wastewater using thermal sensitizer at room temperature. At the optimal component condition, the removal rate of adsorption and thermocatalytic degradation processes can reach the highest level of 82.07% solely response to temperature in the dark. Moreover, the kinetics of degradation rate was modeled considering that it was found similarly to Langmuir-Hinshelwood behavior, and a tentative mechanism was objectively established, describing reasonably well in line with the experimental results. On the other hand, it was found that high amount of methylene blue (MB) adsorbed onto thermal sensitizer was of unambiguous importance to subsequent thermocatalytic performance. Briefly, all above suggest that the feasibility to the thermodegradation route has been successfully verified under room temperature excitation. Herein the insight into degradation pattern of dye over thermal excitation may further enlarge applications for wastewater treatment.

Preparation of mid-to-high molecular weight konjac glucomannan (MHKGM) using controllable enzyme-catalyzed degradation and investigation of MHKGM properties

Mid-to-high molecular weight konjac glucomannan (MHKGM) powders with different molecular weights were prepared and purified from their enzymatic hydrolysis solutions. MHKGM powder yield was optimized with respect to substrate concentration, urea concentration, the number of alcohol washings, and drying temperature. Properties of MHKGM powder were characterized by SEC, FTIR, UV, XRD, rheological, and thermal analysis techniques. The results showed that under the correct conditions a high productive yield of MHKGM can be obtained. MHKGMs have the same chemical structure as that of native KGM, but their weight average molecular weight (Mw), molecular weight distribution index (Mw/Mn), radius of gyration (Rg), solution optical clarity, rheological properties, and other physical properties such as water solubility are very different from those of native KGM. This study provides useful a reference for making MHKGM powder with varying molecular weight and the potential applications of KGM such as healthy food additives.

Adsorption of phosphorus from slaughterhouse wastewater by carboxymethyl konjac glucomannan loaded with lanthanum

Phosphorus removal was an important measure in the control of eutrophication of water environment. In this study, a novel phosphorus removal adsorbent of lanthanum-loaded carboxymethyl konjac glucomannan microspheres (CMKGM-La) was successfully prepared by the method of electrostatic spraying and sol-gel, and was characterized by SEM, XPS and EDX. Batch experiments were performed to evaluate the adsorption capacity at different conditions: pH, temperature, initial concentration, adsorbent dosage and contact time. The results showed that the adsorption kinetics data correlated well with the pseudo-second-order kinetic model and the adsorption isotherm was well described by the Langmuir isotherm model with the maximum capacity of 16.06 mg·g-1 for CMKGM-La microspheres at pH of 4 and 318.15 K. The adsorption of phosphorus was a spontaneous, entropy-increasing and endothermic process. The possible adsorption mechanism of phosphorus on the CMKGM-La microspheres consisted of the coordination reaction of La (III) with phosphorus and electrostatic attraction between protonated hydroxyl and phosphorus. The presence of co-existing ions (such as NH4+, Cl-, SO42-, SiO32- and CO32-) had no significant effect on phosphorus removal. These results suggested that the adsorbent of CMKGM-La microspheres was a promising adsorbent for the removal of phosphorus from slaughterhouse wastewater.

Preparation, Characterization, and Adsorption Properties of Amino-Alky Cellulose for 2, 4, 6-Trinitrotoluene

A novel adsorbent, amino-alky cellulose (AmAC), is prepared by chlorination and amination of hydroxyethyl cellulose (HEC). AmAC are characterized by 13C-NMR and used as adsorbent to remove 2, 4, 6-trinitrotoluene (TNT) from waste water. Effects of various parameters including solvent and amine group content are studied. Adsorption mechanisms are also analyzed. Results show that the maximum adsorption capacity is 69.23 mg g−1 and removal efficiency of 99.30%, while the adsorption deeds are attributed to the hydrogen bond between TNT molecules and amino-alky cellulose. The equilibrium sorption is well demonstrated by Freundlich isotherm model. The reusability experiment shows the adsorbed TNT could be desorbed by ethanol eluant when the pH is 1.