Studies on the use of power ultrasound in solid–liquid myrobalan extraction process

Focus on eco-friendly processing techniques makes vegetable tanning a viable option in leather processing and establishes the subsequent need for the more efficient methods of extraction in tannin manufacture. Application of ultrasound has been tried in the extraction of tannins from myrobalan nuts in order to improve the extraction efficiency, to perform the extraction under milder process conditions and to reduce the process time. The influence of process parameters such as ultrasonic output power, time and temperature has been studied. Scale-up trials and the use of ultrasound in pulse mode have also been attempted. The results show that a three- to fivefold improvement is possible with ultrasonic output from 20 to 100 W. Extraction efficiency has been calculated from the maximum extractable materials from myrobalan nuts. Extraction efficiency is found to be 90% for ultrasound, 100 W without external heating as compared to 77% for control process at 70 °C for 4 h. Therefore, ultrasound could be employed even dispensing with provision for temperature controls. The use of ultrasound in pulse mode offered 70% extraction efficiency of continuous mode. Scale-up trials indicate that there exists an optimum ultrasonic output power depending on the amount of nuts used, to achieve better extraction efficiency. The effectiveness of ultrasonically extracted tannin solution has also been tested in the tanning process for its applicability. The degree of tanning efficacy has been assessed by shrinkage temperature measurement. The results indicate that ultrasonically extracted tannin solution is suitable for tanning process. Therefore, application of ultrasound in tannin extract manufacture is a viable option with added advantages.     

Assessing the impact of leather industries on the quality of water discharged into the East China Sea from Wenzhou Watersheds

Ammonium nitrogen and total germanium are among the main pollutants in the wastewater discharged from the leather industry. The intake of high concentrations of ammonium nitrogen and/or total germanium harms human health and biological species, as is well documented in literature. This paper focuses on assessing the trends of ammonium nitrogen and total germanium concentrations through time in two watersheds (Aojiang and Oujiang) in the Wenzhou metropolitan area of Zhejiang Province and their relationships with the released wastewater using regression and correlation statistics. The paper also utilizes the integrated pollution index to evaluate water quality in the two watersheds. Preliminary results show that, from 1992 to 1998 in the Aojing watershed, the concentrations of ammonium nitrogen and total germanium increased 13 and 14 times, respectively, decreasing somewhat after 1998, while between 1992 and 1997 in the Oujiang watershed, the concentrations increased, then decreased after 1997. The concentrations of ammonium nitrogen and total germanium are positively related to the amount of released wastewater. The concentrations of ammonium nitrogen and total germanium exceeded water standards 12 and 3 times, respectively, in Pingyang county of the Aojiang watershed, 14 and 3.3 times in Lucheng District of the Oujiang watershed, and 14 and 3.8 times in the Ouhai Oujiang watershed, respectively. In Pingyang county of the Aojiang watershed, the water quality degraded from Type III in 1992 to over Type V in 2003, and in the Oujiang watershed, the water quality degraded from Type II to over Type IV in 1999, when they were compared with the water quality standards. The water quality slightly improved in 2003 for the Oujiang watershed. It appears that pollution did have a direct positive correlation with leather industry production in the Pingyang Aojing watershed, while there was a negative correlation between the two in the Oujiang watershed. In these two watersheds, the integrated pollution index did not appear to relate to population dynamics and agricultural production. This paper also discusses the current new methodologies and approaches adopted nationally and internationally to reduce the contaminants and purify the environment for maintaining a sustainable and healthier environment in Wenzhou.     

革用水性聚氨酯的研究

为适应可持续发展的需要,有必要寻找水性聚氨酯产品来替代原有产品。通过大量研究试验,对不同原材料进行对比筛选,已经开发出一批在模最、透湿量、耐挠等许多性能方面都较好的溶剂型聚氨酯浆料的水性浆料。     

Natural and anthropogenic contamination of the Fratta-Gorzone river (Veneto, Italy)

Stream-bed sediment samples were collected in 2001 and 2004 along the Fratta-Gorzone River (Italy) to assess the level of heavy metal contamination. The river stretch most affected by discharges of tannery effluent showed total and pseudo-total Cr levels (up to 2,860 mg/kg) that greatly exceed national and international chemical sediment quality standards. The most contaminated section of the river bed is located downstream of the main industrial discharge. However, a large fraction of the Cr present in the sediment appears to be of lithogenic origin. At most sites, more than 50% of Cr is not soluble in aqua-regia and thus unlikely to be very mobile or easily bio-available. A negligible risk to the benthic community can be inferred for Pb, Zn, Cd, Cu and Ni. This work highlights the limitation of using existing chemical sediment quality standards alone for risk assessment. The collection and analysis of suspended solids, the determination of river discharge and of dissolved Cr at 10 field stations allowed to estimate the particulate and dissolved Cr load and to locate the river stretch that was the likely source of contaminated sediment. The pumping of dilution water from the Adige River into the Fratta-Gorzone River did not produce the expected contaminant dilution effect due to re-suspension of contaminated solid particles and the release of Cr in solution.     

A potential new commercial method for processing leather to reduce environmental impact

INTRODUCTION: Current leather processing method involves dehairing and fibre opening employing lime and sulphide, which results in higher negative impact on the environment due to its uncleanness. This method of dehairing and fibre-opening process accounts for nearly 70-80% biochemical oxygen demand and chemical oxygen demand (COD) in tannery wastewater and also the generation of H(2)S gas. MATERIALS AND METHODS: Hence, an attempt has been made to reduce the environmental impact of the leather processing through a biochemical approach, employing proteolytic enzyme and sodium metasilicate for performing the above process more cleanly. RESULTS AND DISCUSSION: The developed process exhibits significant reduction in environmental parametres such as COD and total solid loads by 55% and 25%, respectively. This method completely avoids the formation of lime sludge. CONCLUSION: The functional properties of the leathers are also on par with conventionally processed leathers. Further, the process seems to be commercially viable.     

SBR生化法在制革废水处理中的应用

结合实际工程经验,比较了几种常用的生化法在制革废水治理中的应用,对运用SBR生化法处理制革废水的工艺设计、运行管理进行了探讨,表明SBR生化法治理制革废水具有耐冲击性能佳,操作运行管理方便,建设成本和运行费用较低等优点。     

Conversion of leather wastes to useful products

The main objective of the present study is to investigate the production of useful materials from different kinds of leather waste. Three different types of tannery wastes (chromium- and vegetable-tanned shavings, and buffing dust) were pyrolyzed in a fixed bed reactor at temperatures of 450 and 600 °C under N₂ atmosphere. Gas, oil, ammonium carbonate and carboneous residue were obtained by pyrolysis. The effect of temperature and type of leather waste on product distribution of pyrolysis was investigated. Buffing dust gave the highest yield of oil (ca. 23%), while other wastes recorded yields of ca. 9%. Results of elemental analysis and column chromatography showed that pyrolysis oils could be used as fuel or chemical feedstock after re-treatment. The yields of carboneous residue (chars) were between 37.5% and 48.5% and their calorific value was between 4300 and 6000 kcal kg⁻¹, suitable for use as solid fuel. In addition, these chars were activated by CO₂ to obtain the activated carbon. The activated carbon having highest surface area (799.5 m² g⁻¹) was obtained from chromium-tanned shavings. Activated carbons prepared from chromium-tanned leather were presented as an adsorbant for the adsorption of dyes from aqueous solution.     

生物法和化学法回收制革污泥中铬的对比研究

研究了嗜酸性硫杆菌(Thiobacillus)生物沥滤法和1:1硫酸化学沥滤法分离回收制革污泥中的铬.比较了嗜酸性硫杆菌生物沥滤法和化学沥滤法回收制革污泥铬过程中pH、氧化还原电位(ORP)、沉降比(SV)以及铬的沥滤率的变化.试验结果表明,pH是影响制革污泥中铬的沥滤率的关键因素.生物沥滤法在使污泥pH大幅度降低的同时,能很好地改善污泥的沉降性能,对铬的沥滤效果好于化学沥滤法.