Minimization of the environmental impact of chrome tanning: a new process reusing the tanning floats

A chrome tanning process which allows the reuse of tanning floats has been developed. The most commonly used chromium salts were replaced by highly masked and basified ones. This substitution eliminates basification operation and prevents pH change and the considerable neutral salts concentration increase in the tanning float. Consequently, tanning float can be reused several times. An optimum chromium salt concentration in the tanning float between 10% and 12.5% has been determined. It has been shown that the number of times the tanning float can be reused depends on the quality of the leather grain to be manufactured. In the best case, a saving of 18 L of water per kilogram of tanned leather is calculated. This means savings of 90% of water normally used.     

基于鞣制工艺参数的铬污泥产污系数核算方法

针对无明确化学计量关系、均相或非均相封闭系统的一次性化工过程中产生的具有固定组成的污染物,其单位产品污染物产生量(即产污系数)的实测会因产品加工周期与污染物产出量相脱节而得不到准确值.制革行业铬鞣工段的诸多工艺参数对皮中铬的吸收率具有显著影响,通过实验室试验及历年工艺手册数据整理,在建立单一工艺参数与铬吸收率之间的关系基础上,采用逐步优化回归分析法,建立了鞣制工艺参数与铬污泥产生量之间的定量关系,并与企业实测铬污泥数据进行了对比.结果表明,通过工艺参数计算的铬污泥产污系数完全可以反映实际情况.      

Recovery and reuse of chromium from chrome tanning waste water aiming towards zero discharge of pollution

The leather industry faces very challenging task because of the regulations enforced by the various pollution control bodies to maintain the discharged norms of the chemical in the treated water. The pollution due to the use of chromium and other chemicals in the leather industry is critically analyzed for the harmful effects. Many studies have been undertaken to optimize the amount of chemicals used in leather processing. The pollution due to chromium is one of the major constraints in the leather processing operation. Chrome recovery and reuse methods have become the compulsory recovery methods in the leather industry to recover and reuse the chromium present in the effluent. Several precipitation methods are emerging but still they are not feasible. In this paper, an attempt has been made to recover the chromium present in spent tan liquor using neutralized wattle extract. The wattle extract at different pH conditions (pH 7, 8, and 9) was used for recovery of chromium. The neutralized wattle extract was made to react with chromium in the spent liquor and allowed to settle for a period of 6 h. Major amount of chromium settles at the bottom leaving minimal amount in the supernatant. The chrome was recovered and reused for tanning the pelt. The wattle extract that was left in the tanning bath was reused for post-tanning process as a retanning agent. Therefore, complete utilization of the chromium and wattle extract has been achieved in this work. It has also been noticed that increased level of chrome exhaustion of 85% and 87% (precipitate and supernatant) in experimental leather could be obtained in comparison with the exhaustion of 74% in control sample. The physical strength and color properties of the experimental leather were comparable to the control leather. The overall results show that the recovered chromium can be well used for tanning purpose to obtain the leather of comparable properties.     

Water reuse in tannery beamhouse process

In tanneries, the phases of conditioning and preparing the hide for tanning, as well as the transportation and fixation of tanning substances, are all carried out in aqueous media. Most of the steps of these processes are carried out with fresh water, which is used as a vehicle for the diffusion of chemical products and the extraction of undesirable materials from the hide. The objective of this study is to provide the minimization of water consumption at tanneries by applying the reuse of water at some stages of the process. Alternatives for water reuse were evaluated through analysis of the process wastewater to determine the concentration of some contaminant parameters. In tests with half-hides, the possibility of reusing the liquors from the 2nd bating washing in the 1st bating washing, and of reusing the liquors from the pre-deliming washing in the pre-deliming operation, was verified. In industrial scale the water reuse from a mixture of bating washings in the deliming and deliming bating was tested successfully. The quality of wet-blue leather analyzed in the systems with and without water reuse did not show any considerable differences and satisfies the tannery specifications. Finally, a mathematical program for mass integration was applied to solve the problem of water reuse in the beamhouse steps.     

Power ultrasound in fatliquor preparation based on vegetable oil for leather application

In recent years, power ultrasound has taken a significant place in chemical and physical activities of the process industries as an effective and non-polluting method of activation. Oil in water emulsions known as fatliquors are used for the lubrication of tanned leather fibres to get softness and also to improve the strength properties. In the present study, ultrasound has been used as a tool for the preparation of fatliquor emulsion for application in leather fatliquoring process. An emulsion is a fine dispersion of one liquid in another liquid. Sulphation is one of the common methods followed to prepare fatliquor emulsion where sulphuric acid is used. In the conventional process, emulsifying agent is also added to increase the stability of oil in water emulsions. The emulsifying agents generally used are chemicals or metal soaps. The potential use of ultrasound in the preparation of stable oil in water emulsions dispensing with sulphation process and with the minimum use of emulsifying agent has been studied and reported in this paper. This process enjoys the benefit of less pollution load in the form of chemical entities. The studies included the effect of process parameters such as ultrasonic output power and amount of oil used. Fatliquor emulsion prepared using ultrasound has been applied in leather fatliquoring process and the strength properties of the leathers were assessed. Emulsion particle size, which is another important parameter for diffusion through leather, has been measured using Laser Diffraction Technique. The stability of the ultrasonically prepared fatliquor emulsion has been found to be good. The results indicate that ultrasound could be effectively utilized in the preparation of non-ionic fatliquor emulsion eliminating sulphuric acid and impart required properties in leather.     

Reducing the environmental impact of the unhairing–liming process in the leather tanning industry

The environmental impact of the tanning industry is generally significant with outputs of wastes, i.e. high concentrations of organics, salts and heavy metals (chromium compounds), both in solid and liquid form, as a result. In order to bring the tanning industry more in line with present environmental thinking, various methods have been devised to reduce impacts.The underlying study proposes a modification of the method for unhairing–liming of hides where the unhairing–liming liquids are reused several times after being recharged by reduced quantities of chemicals. The study, therefore, aims at reducing both the economic and environmental costs of the unhairing–liming process.Experiments were carried out at lab scale with a simulation apparatus designed for the purpose. Life cycle assessment was used to evaluate the net environmental benefits of the modified method. The present value approach was used to evaluate the economic feasibility of the modified method. The quality of the produced leather was assessed by experts from the tanning sector (tanners).On the environmental level, the modified method reduced the environmental impact of the process by 24%, COD was reduced by 50% as well as sulfide which was reduced by 73% when the process water was recycled four times.The modified method requires some investment in new equipment and is a little more labor intensive as compared with the conventional method but does permit for savings in water up to 58% and chemicals up to 28% as well as wastewater treatment cost which was reduced by 58%. The modified method allowed for four times reuse of the unhairing–liming liquor without visibly affecting the quality of the final product of leather.It was concluded that both the economic and the environmental costs of the unhairing–liming process were reduced relative to the same of the conventional method.     

桥式刮油刮渣机的发展及应用

桥式刮油刮渣机是一种新型高效连续运行的水处理设备,非常适用于冶金、矿山、煤炭化工、造纸、印染、皮革、电镀等工业废水的处理,既可刮渣又可刮油,以达到废水回用的目的,介绍了桥式刮油刮渣机的分类,并对其发展与应用进行深入分析。     

Reclamation treatment of the chrome leather scrap

ＩｎｔｒｏｄｕｃｔｉｏｎＣｈｒｏｍｅｌｅａｔｈｅｒｓｃｒａｐｉｓｔｈｅｓｏｌｉｄ ｗａｓｔｅｏｆｌｅａｔｈｅｒｉｎｄｕｓｔｒｙ .Ｉｔｓｍａｉｎｃｏｍｐｏｓｉｔｉｏｎｉｓｐｒｏｔｅｉｎ(ｍａｉｎｌｙｃｏｌｌａｇｅｎｐｒｏｔｅｉｎ ,ｇｌｏｂｕｌｉｎａｎｄａｌｂｕｍｉｎ) ,ｓｏｍｅＣｒｃｏｍｐｏｕｎｄｂｏｎｄｉｎｇｗｉｔｈｔｈｅｐｒｏｔｅｉｎ ,ａｌｉｔｔｌｅｃａｒｂｏｈｙｄｒａｔｅ ,ｆａｔａｎｄｓｏｍｅｉｎｏｒｇａｎｉｃｓ.Ｔｈｅｃｈｒｏｍｅｌｅａｔｈｅｒｓｃｒａｐｓｔａｃｋｅｄｗｉｌｌｐｕｔｒｉｄｇｒａ…     

Recouping the wastewater: a way forward for cleaner leather processing

Leather processing employs copious amounts of water. This leads to the generation of enormous amounts of liquid effluent. The high effluent volume requires huge investments for effluent treatment plants in order to meet the required specification for the discharge of liquid effluents to various water bodies. Increasingly therefore, water use minimization in leather processing assumes greater significance due to increased treatment costs. End-of-pipe treatment methods alone do not meet the requirements and hence, in-plant control measures are gaining importance. The new era of cleaner technology has begun in leather processing. Pre-tanning and tanning operations contribute about 57% of the water consumption in leather processing and the washings about 35%. The proper adoption of integrated cleaner technologies provides a viable solution to the conservation of water in leather processing. This paper presents an integrated approach for water use minimization through recycling and optimization in leather processing. The integrated approach provides considerable reduction in the use of process water.     

水质型缺水城市污水再生回用探讨

系统分析了水质型缺水城市污水再生回用的意义、可行性和用户的选择,对回用中存在的障碍及其相应的对策进行分析,以期为水质型缺水城市污水再生回用提供参考.     

汽车内装饰材料挥发性有机物GC-MS测定和分析

采用恒温测试箱法采集汽车内部装饰材料释放的挥发性有机物,利用Nutech预浓缩仪对样品进行三级VOC富集,然后用GC-MS法(气相色谱-质谱法)对汽车内部装饰材料释放的挥发性有机物苯、甲苯、二甲苯、乙苯、苯乙烯进行了测定,检出限低于2.0μg/m3。实验选择皮革表皮、橡胶密封条、灰色无纺布、海棉和仪表盘五种汽车内部装饰材料,进行挥发性有机物含量的测定,并对结果进行了分析和讨论。结果表明五种汽车内部装饰材料均不同程度地释放挥发性有机物,其中热塑性材料仪表盘释放出的TVOC含量最高,橡胶密封条的TVOC释放量也较高,皮革表皮和灰色无纺布释放的甲苯较多,而消音材料海绵主要释放出二甲苯。汽车内部装饰材料释放挥发性有机物的情况复杂,因此,探索和建立有效的汽车内部装饰材料有害物质检测方法,对于选择低毒环保的汽车内部装饰材料非常有意义。     

Screening of leather auxiliaries for their role in toxic hexavalent chromium formation in leather—posing potential health hazards to the users

With increasing concern about the potential health hazards of toxic chemicals in consumer articles such as leather products, many countries importing these articles have introduced stringent stipulation for the permissible levels of such chemicals in these articles. Hexavalent chromium is one such toxic metal ion included in the list of regulated substances. The problem is unique to leather industry as it uses only trivalent chromium based salts in the tanning process but faces the problem of presence of Cr(VI) in the end product. Efforts are being made to understand the reasons for the presence of hexavalent chromium in leather and to devise strategies for eliminating the same in processing. This paper describes our attempt to investigate the role of potential post-tanning (wet finishing) and finishing auxiliaries used in leather processing in the conversion of Cr(III) to Cr(VI) in the chrome-tanned leather. The auxiliaries were also screened for the presence of oxidizing functionality and the amount estimated as persulfate. The study reveals that the auxiliaries suspected of having a role in Cr(VI) formation do have considerable quantities of residual oxidizing functionality capable of converting Cr(III) to Cr(VI). The study with persulfate as the model oxidizing agent confirms the role of oxidizing agents in the formation of quantities of Cr(VI) well above the permissible limit of 3 mg/kg in leather matrix, which basically provides a reducing environment.     

激光烧蚀皮革过程中的废气成分研究

皮革在激光烧蚀过程中会产生大量具有恶臭气味的有机废气,严重影响空气质量。为了评估该类型气体危害,分别利用紫外可见分光光度计和气相色谱-质谱联用仪,检测了天然皮革和人造革在激光烧蚀过程中的废气成分。结果显示烧蚀天然皮革所产生的废气中含有NO、NO2、SO2、二氨基丙烷和丙烯酸甲酯,烧蚀人造革所产生的废气中含有NO、NO2、甲硫醇、二硫化碳、乙二醇、二甲基二硫醚、丙二醇、乙二醇二甲醚和硫代乙酸甲酯。其中,甲硫醇、二硫化碳、二甲基二硫醚和乙二醇二甲醚都是产生恶臭的有机成分。研究为该类型废气的治理提供了基础数据和依据。     

PU合成革废水治理分析

生产聚氨酯（PU）合成革的废水中含有高浓度有机物,其中N,N-二甲基甲酰胺（DMF）毒性大,难生物降解.文章阐述了合成革的生产工艺,分析该过程中DMF废水形成阶段、处理现状及其处理方法.结合各种方法的优缺点,展望了DMF废水的处理研究方向.     

PU合成革废水治理分析

生产聚氨酯（PU）合成革的废水中含有高浓度有机物,其中N,N-二甲基甲酰胺（DMF）毒性大,难生物降解。文章阐述了合成革的生产工艺。分析该过程中DMF废水形成阶段、处理现状及其处理方法。结合各种方法的优缺点,展望了DMF废水的处理研究方向。     

A cleaner production method for the synthesis of bronopol – A bactericide that is useful in leather making

In leather industry environmental concern has been growing since 1980s. Increasing levels of pollutant emissions have reached saturation point in spite of the conventional technology that highly industrial countries have adopted to keep them under control. This has started a technology revolution in several industries. These critical levels of pollution may have been caused by high industrial density, by high population density or by the use of old polluting technology. This situation has boosted emerging green technology which has begun to take up a larger portion of research work in the supply and raw materials in industries. Together with consumers growing awareness of the environment, this new technology has ended up affecting the consumer good industry. In leather industry due to the sector's bad public image regarding pollution more emphasis has been given to clean technologies and waste reduction. At this time nearly every part of the tanning process has several cleaner or environmentally friendlier alternatives. In leather industry to prevent damage to the hide and skin, bactericide is added during soaking process to kill the growth of microorganism. Bronopol is used as a bactericide. The active ingredient of bronopol is 2-bromo-2-nitropropane-1,3-diol. Here we have reported simple and cleaner technology of the bronopol by using nontoxic and non-hazardous raw materials and belongs to the modern concept of environmentally friendly low waste or nonwaste technology. Bronopol was characterized by IR and Mass spectral data.     

流化床锅炉溢流渣余热回收和冷渣的综合利用

介绍了流化床锅炉溢流渣余热利用和冷渣变废为宝的途径。     

生物滴滤塔处理制革恶臭气体微生物特性研究

在生物滴滤塔处理制革恶臭气体中,采用SBR法对活性污泥进行驯化,考查生物滴滤塔处理制革恶臭气体中微生物的特性。研究了微生物对氨氮和硫化物的去除效率以及驯化过程中污泥容积指数(SVI)的变化,并对挂膜后填料表面的微生物相进行扫描电镜观察。结果表明:经过19 d的驯化,微生物对氨氮和硫化物的去除率分别可以达到98.29%和94.16%,驯化期间污泥容积指数均保持在正常的范围之中。挂膜14 d的扫描电镜显示,填料表面有均匀的生物膜分布,说明微生物在填料上已经挂膜成功,驯化的微生物可以达到去除制革恶臭气体的要求。     

Cleaner tanning practices for tannery pollution abatement: Role of enzymes in eco-friendly vegetable tanning

Concern about pollution related problems in the global scenario are persuading all the processing industries to adopt cleaner manufacturing practices. Thus, the leather industry is also under pressure to look for effective alternative tanning materials for chromium. Natural products like vegetable tannins are regaining importance. However, there are limitations in the use of vegetable tanning materials because of its high organic load in the effluent, which are difficult to degrade leading to high chemical oxygen demand (COD). Moreover, conventional vegetable tanning process requires partial pickling that involves the use of sodium chloride, to suppress osmotic swelling. This results in very high amount of total dissolved solid (TDS) content in wastewaters. In this investigation, an attempt has been made to design an eco-friendly vegetable tanning process combining pickle-free tanning and application of proteolytic enzymes to improve the exhaustion of vegetable tannins. Such an approach has resulted in more than 95% tannin exhaustion in the case of the experimental process, an increase of 10% compared with the conventional vegetable tanning process. The tanned leathers showed slight improvement in hydrothermal stability. Physical and tactile evaluation of experimental leathers has been better than conventionally tanned leathers. Surface colour values illustrated negligible variation in colour and shade between control and experimental leathers. The resultant leather showed opened up, split compact fibre structure that has been well coated, indicating that the enzyme assisted tanning process did not bring about any major change or destruction on the fibre structure of the leathers. The optimized system has been field tested in a commercial tannery. The results showed that the enzyme assisted tanning process is efficient in terms of improved quality of leather and also led to reduction in total solids (TS), chlorides and COD loads. The enzyme assisted tanning system presented appears to be a viable option for combating pollution arising from the conventional vegetable tanning system.     

废旧冰箱塑料回收再生利用技术研究

目前我国的废旧冰箱已进入了一个报废高峰期，且大量废旧冰箱塑料的处理问题已成为当今地球环境保护的热点问题，而我国又是一个人均资源占有量很低的国家，因此，对废旧冰箱塑料进行回收与再生利用则具有极其重要的意义。介绍了废旧冰箱塑料的物理再生利用、化学再生利用、生物降解、能源回收利用的技术和方法。