• Energy Research
• Closed Access close
• 6. Clean water close
• CN close
• CA close
• GB close

Abstract In this study, crude cellulose derived from cornstalk, after bleaching, was used as raw material for the synthesis of sodium carboxymethyl cellulose (CMC) by reacting with the cellulose with NaOH and chloroacetic acid at 75 °C for 1.5 h. Effects of alkali dosage, concentration of chloroacetic acid on the physical and chemical properties of the CMC products were investigated. It was revealed that the reactants alkali reagent/chloroacetic acid/cellulose at the molar ratio of 4.6:2.8:1and 4:2.5:1, or at the molar ratio of NaOH/ClCH 2 COOH ≈1.6–1.64, resulted in CMC products of relatively high water solubility. The viscosity-average molecular weight M v of these two CMC products obtained at molar ratios of 4.0:2.5:1 and 4.6:2.8:1 is in the range of 1.94 × 10 4 –2.48 × 10 4 g mol −1 , and the average DS of the two products are 0.57 and 0.85, respectively. As the solute concentration is above 2 wt%, the viscosity of the CMC-water solution exhibits nonlinear (exponential) increasing with increasing the solute concentration (typical of non-Newton fluids).

The microbial electrolysis desalination and chemical-production cell (MEDCC) is a device to desalinate seawater, and produce acid and alkali. The objective of this study was to enhance the desalination and chemical-production performance of the MEDCC using two types of stack structure. Experiments were conducted with different membrane spacings, numbers of desalination chambers and applied voltages. Results showed that the stack construction in the MEDCC enhanced the desalination and chemical-production rates. The maximal desalination rate of 0.58 ± 0.02 mmol/h, which was 43% higher than that in the MEDCC, was achieved in the four-desalination-chamber MEDCC with the AEM-CEM stack structure and the membrane spacing of 1.5mm. The maximal acid- and alkali-production rates of 0.079 ± 0.006 and 0.13 ± 0.02 mmol/h, which were 46% and 8% higher than that in the MEDCC, respectively, were achieved in the two-desalination-chamber MEDCC with the BPM-AEM-CEM stack structure and the membrane spacing of 3mm.

Microwave-assisted alkali pre-treatment of wheat straw and its enzymatic hydrolysis were investigated and compared with the conventional alkali pre-treatment process. First, the effect of microwave power and pre-treatment time on the weight loss and composition of wheat straw was examined. The results show that the higher microwave power with shorter pre-treatment time and the lower microwave power with longer pre-treatment time had the same effect on the weight loss and composition at the same energy consumption. The comparison was then made between the effect of the microwave-assisted alkali pre-treatment and the conventional alkali one on the weight loss and composition of wheat straw. The wheat straw had a weight loss of 48·4% and a composition of cellulose 79·6%, lignin 5·7% and hemicellulose 7·8% after 25 min microwave-assisted alkali pre-treatment at 700 W, compared with a weight loss of 44·7% and a composition of cellulose 73·5%, lignin 7·2% and hemicellulose 11·2% after 60 min conventional alkali pre-treatment. The microwave-assisted alkali pre-treatment removed more lignin and hemicellulose from wheat straw with shorter pre-treatment time compared with the conventional alkali one. Finally, the enzymatic hydrolysis of pre-treated wheat straw (substrate concentration 50 g l−1, enzyme loading 20 mg g−1 substrate) was also investigated and the results indicate that the microwave-assisted alkali pre-treated wheat straw had higher hydrolysis rate, reducing sugar concentration and glucose content in the hydrolysate than the conventional alkali pre-treated one. Microwave-assisted alkali pre-treatment is a potential alternative of wheat straw pre-treatment for its enzymatic hydrolysis.

Among various bioreactors examined in anaerobic digestion and dark fermentation, UASB bioreactor has shown to be a promising alternative. However, mass transfer resistance and biomass washout have been the issues that reported as draw backs of the granular system in the literature. Another problem associated with such a system is its long start-up period as a result of biomass washout and long microbial granulation stage. In this paper, the results obtained from an UASFF bioreactor in methane (AD process) and hydrogen (DF process) production from POME, are presented to assess mass transfer of substrate into the granules and also study the role of internal packing used in the middle part of reactor in the process stability. The value of effectiveness factor, η, for AD and DF processes were calculated to be 0.96 and 0.94, respectively, indicating that there was no mass transfer resistance due to internal and/or external factors. The results showed that the packing material could retain biomass in the reactor and had outstanding contribution in the granulation enhancement. Its role as a supplementing treatment stage was more significant at low HRTs and up-flow velocities.

Abstract In this paper, coupled governing equations were proposed to simulate three-dimensional heat conduction and moisture transport in the nuclear waste repository. Because there will be a large temperature gradient near inner and outer boundaries of the bentonite buffer layer, and the heat driven moisture transport is introduced in the governing equation of moisture transport. By applying the Fourier and Laplace transforms, the governing equations were converted to the Bessel equations, and the Laplace-domain solutions to temperature and moisture distributions were derived through the inverse Fourier transform. The reliability of the proposed solutions was verified through comparative analysis with the line heat source model. These analytical solutions were applied to obtain the evolutions of temperature field and moisture distribution near the waste canister. Finally, a sensitivity study was performed to analyze the effects of relevant parameters on the heat driven moisture transport.

Forest soil acidification caused by acid deposition is a serious threat to the forest ecosystem. To investigate the liming effects of biomass ash (BA) and alkaline slag (AS) on the acidic topsoil and subsoil, a three-year field experiment under artificial Masson pine was conducted at Langxi, Anhui province in Southern China. The surface application of BA and AS significantly increased the soil pH, and thus decreased exchangeable acidity and active Al in the topsoil. Soil exchangeable Ca2+ and Mg2+ in topsoil were significantly increased by the surface application of BA and AS, while an increase in soil exchangeable K+ was only observed in BA treatments. The soil acidity and active Al in subsoil were decreased by the surface application of AS. Compared with the control, soluble monomeric and exchangeable Al in the subsoil was decreased by 38.0% and 29.4% after 3 years of AS surface application. There was a minimal effect on soluble monomeric and exchangeable Al after the application of BA. The soil exchangeable Ca2+ and Mg2+ in the subsoil increased respectively by 54% and 141% after surface application of 10 t ha-1 AS. The decrease of soil active Al and increase of base cations in subsoil were mainly attributed to the high migration capacity of base cations in AS. In conclusion, the effect of surface application of AS was superior to BA in ameliorating soil acidity and alleviating soil Al toxicity in the subsoil of this Ultisol.

This study focused on the effects of plant compositions on removal rates of pollutants in microcosms through investigating rhizosphere microbial populations, photosynthetic efficiency and growth characteristics. Mixed-culture groups improved the removal efficiency of TN and TP significantly but exhibited lower COD removal rates. Total plant biomasses were improved as the species richness increased, but the N/P content in the plants was mainly affected by the type of species. The mixed-culture groups showed lower photosynthesis rates and oxygen supply generated from roots under high irradiation. Microbial communities of the cultured groups in the rhizosphere exhibited significant differences. According to principal component analysis (PCA), the fungi were the typical microbes of SPA, SPAB, and SPABC, resulted in improvement in nutrient accumulation. These results demonstrated that a mixed culture strategy can represent the overyielding of biomass, promote the photo-protection mechanism, and will further increase the removal rates of pollutants in a constructed wetland.

Abstract CBM reservoirs are extremely vulnerable to damage due to their complex pore structure. So, changing pore structures in CBM reservoirs is of vital importance for reducing reservoirs damage. Organic solvents have been considered as additives into fracturing fluids to enhance production because they can enhance the pore connectivity and loosening macromolecular network structure. It is thus of great interests to investigate how organic solvents (ethanol and ethylene glycol ether) change micropore structures and fluid distribution. In this study, samples were selected from different wells completed in No. 3 coal seam, Zhaozhuang minefield. Low-pressure nitrogen adsorption (LP-N2GA) experiments were conducted on coal samples to evaluate the changes in pore-structure parameters including specific surface area (SSA), pore diameter, and pore volume. NMR experiments were conducted on coal samples to evaluate the changes in fluid distribution. Analyzing the LP-N2GA results suggests ethylene glycol ether and ethanol can effectively increase SSA, pore diameter, and opening degree of pores in coal samples. Comparative analysis of NMR results indicates that ethylene glycol ether consistently reduces the irreducible water saturation (Swir) in samples. The average value of Swir of raw samples is 0.8670 and the average value of Swir of samples treated with ethylene glycol ether value is 0.7644. Considering the pore-structure alterations, this study demonstrates that ethylene glycol ether is more preferable for enhancing recovery from CBM reservoirs compared with ethanol.

The operation of centrifugal pumps can generate instabilities and pressure pulsations that may be detrimental to the integrity and performance of the pump. In the present study a numerical investigation of the time variation of pressure within a complete centrifugal pump was undertaken. A range of parameters and three flow rates were investigated and the pulsations were extracted at 15 different locations covering important pump regions. The transient flow results compared reasonably with experimental data obtained in a limited experimental survey and clearly indicated the pump locations experiencing the largest pulsation levels. It was also noted that monitoring pulsations at the top dead centre of the pump volute casing would provide a better indication of internal pump pulsations than monitoring at the discharge.