A salt-free pickling regime for hides and skins using oxazolidine

During the last few decades new materials and technologies have being studied and applied in order to reduce the ecological impact of leather production. Severe restrictions imposed by the pollution control authorities on the disposal of chromium, total dissolved solids and chlorides in tannery effluents have forced the tanners and researchers to look for eco-benign pickling and tanning processes. In this study, we would focus on the novel process development of pickling with the presence of oxazolidine based product. Investigations indicated that oxazolidine is a potential material to replace neutral salts in pickling and, realize high chrome exhaustion in the subsequential chrome tanning.     

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.     

Reducing sulfates concentration in the tannery effluent by applying pollution prevention techniques and nanofiltration

The use of large quantities of sulfuric acid and other sulfur-containing chemicals causes high sulfate concentrations in the wastewater of a tannery. The aim of this work was reducing the sulfate concentration in the final wastewater from a tannery. For that, firstly a study about the main sulfate sources in a tannery was carried out and the total sulfates load in the tannery wastewater was evaluated. Two measures for sulfates reduction were studied: the recycling of unhairing wastewater to the soaking drums and the reuse of the chromium sulfate from the tanning washing wastewater after its separation by nanofiltration (NF). The first measure proposed was studied experimentally in laboratory drums of 5 L of volume. Two series of experiments with different volumes of unhairing wastewater in the soaking bath were carried out. The quality of the final leather was evaluated by means of mechanical tests. NF experiments were carried out in a laboratory pilot plant with a spiral wounded membrane element. Concerning the results, the combination of 50% unhairing wastewater and 50% of fresh water was appropriate in order to obtain leather with an acceptable quality. Besides, it drove to a diminution of approximately 10% in the addition of sulfide in the unhairing. Related to the NF experiments, 97% of the sulfates were rejected by the membrane. The separated ions could be recycled to the tanning drums. The application of the two measures (firstly the recycling of the unhairing wastewater and secondly the NF of the tanning washing wastewater) drove to a reduction of 14.82 kg SO₄⁻² t⁻¹ of raw hide.     

CAF空穴气浮—生物接触氧化工艺在制革废水处理中的应用

介绍了一种皮革废水处理新工艺，即ＣＡＦ空穴气浮—接触氧化工艺。经预处理的制革综合污水采用ＣＡＦ系统混凝气浮，生物接触氧化工艺处理后，ＣＯＤＣｒ、ＢＯＤ５、ＴＳＳ、ＦＯＧ、硫化物以及总铬的去除率均在９５％以上，可达到回用标准。     

Convenient synthesis of methylene bisthiocyanate as microbiocide

Methylene bisthiocyanate (MBT) is used as a biocide in the leather making industry. Commercial biocidal formulations containing a blend of 10% MBT (Methylene bisthiocyanate) and 10% TCMTB (2-Thiocyanomethylthio)-benzothiazole are available. This blend of active ingredients combine the rapid antimicrobial action of MBT with the fungicidal properties of TCMTB. Such biocides are suitable for use over a wide range of tannery applications including the soaking and pickling stages. This paper reports on a simple and cleaner technology of the synthesis of MBT by using non toxic and non hazardous raw materials and belongs to the modern concept of environmentally friendly low wastes or non wastes technology (LWNWT). From the workers health and safety point of view raw materials such as sodium thiocyanate, water, phase transfer catalyst (Benzyl trithylammonium chloride) and halogenating agent (Bromochloromethane, ethylene bromide, methylene chloride) are used which are non hazardous and non toxic. MBT is characterized by conventional methods, IR ¹HNMR and mass spectral data.     

城市生活垃圾处理中的碳排放及其评价模型研究

城市生活垃圾是温室气体的重要排放源,研究其碳排放评价模型意义重大.本文介绍了温室气体减排的履约机制和垃圾处理碳排放的常用评价模型,并重点强调了CO2ZW模型的适用性和优点,为垃圾处理碳排放的评价引入了新工具.选择适合中国国情和各地特点的碳排放评价模型,有助于推动固废处理行业的低碳生产和保持国民经济的可持续发展.     

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.     

An improved product-process for cleaner chrome tanning in leather processing

Severe restrictions imposed by the pollution control authorities on the disposal of chromium, total dissolved solids and chlorides in tannery effluents have forced the tanners to look for low-waste, high exhaust chrome tanning salts. An improved chrome syntan with more than 90% uptake of chrome has been developed. The new product serves both as tanning and retanning agent and can be applied directly to delimed pelts thus eliminating the conventional pickling stage in the leather processing. This modified process helps to reduce the chemical oxygen demand (COD), total dissolved solids (TDS) and chlorides in the spent tan liquor by 51, 81 and 99%, respectively. The product offers full, soft leathers having shrinkage temperature comparable to conventional chrome tanned skins. Since the developed product is highly reactive, it saves time and reduces the water requirement when compared to the conventional chrome tanning method. Thus the novel product/process developed not only has advantages in reducing pollution loads but also seems to be techno-economically viable.     

面临环保——我国皮毛、皮革业如何发展

在对我国皮毛、皮革业的现状进行分析的基础上,提出一见些具体的改进措施,改进后,在解决环境污染问题的基础上,又能使我国皮毛、皮革业得到可持续发展,尽而在国际市场上能立于不败之地。     

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.     

Reclamation treatment of the chrome leather scrap

A novel method to extract protein and Cr(III) from the chrome leather scrap discarded by leather industry is described.Chrome leather scarp was hydrolyzed under basic condition to remove chromium compound and extract protein. The extracted protein was mixed with substrate and used as feed protein after being dried and ground. The basic residue was treated with sulfuric acid to obtain chrome(III) sulfate which can be used as tanning agent again after adjusting pH with base. The acidic residue was processed and used as flower fertilizer. The safety of the protein powder produced has been by toxicology and nutriology test. This reclamation method has been industrialized.     

A chemo-enzymatic pathway leads towards zero discharge tanning

Leather processing has been an important industrial activity, which has gained significant economic relevance in India. The recent practices of leather manufacture cause difficulties with regard to environmental challenges. The conventional method for making the skins ready for tanning and the tanning by itself employs a wide variety of chemicals which result in an increase in chemical oxygen demand (COD), total dissolved solids (TDS), chlorides, sulfates and chromium in the tannery effluent. In this study, an integrated chemo-enzymatic methodology has been explored which would minimize or to some extent eradicate the unsafe chemicals involved in the process to provide a clean environment. The sequence involves an enzymatic dehairing, NaOH based fibre opening and a pickle-less chrome tanning. The modified process results in decrease in COD and TS (total solids) loads by 67 and 78%, respectively, as compared with control process. The process explored appears to be economically viable.     

Efficient synthesis of 2-(thiocyanomethylthio)benzothiazole

In the leather industry phenolic-based fungicides have been in use until recently. As a result of legislation limiting the content of pentachlorophenol (PCP) in leather, non-chlorophenolics based on 2-(thiocyanomethylthio)benzothiazole (TCMTB) have become more widely used in the leather industry for controlling the growth of fungi and sulphate-reducing bacteria. This paper reports a clean and simple method of synthesis of TCMTB, which is characterized by conventional methods, IR, ¹H NMR and mass spectral data.     

Reclamation treatment of the chrome leather scrap

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

循环经济与温州合成革产业的可持续发展

循环经济是符合可持续发展理念的经济增长模式。将循环经济的理念引入温州合成革产业,通过分析合成革产业可持续发展面临的主要问题,提出了企业内部推进清洁生产、企业之间延伸产业链、行业增强科技创新能力的循环经济发展对策。     

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.     

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。     

Possible steps to follow for filling the gap between requirements and the real condition in tanneries

The tannery industry, as one of most important industrial activities, faced more dilemmas at the fall of communistic era:

• -Can the branch keep a leading position for the exported products at the national level, under a de-centralized system?
• -Can the industry comply with the new, more stringent environmental legislation?
• -How far is this industrial branch from the European BAT/BATNEC?

Facing a completely new perspective for their development, many industrial units had a limited margin for manoeuvre and those not enough flexible had to shut down.“Economic survival whatever the price” has been the mantra for some good years. The newly presented EU legislation has been raising many difficult and complex problems for the units that managed to survive that they need to prioritize their improvement actions.Combining Cleaner Production (CP) measures with laboratory research for technology upgrades can have a synergistic effect for improving environmental performance and decrease resource consumption. The effects were evaluated for more experimented measures, such as better process control, toxics use reduction, and source separation of wastes. The results demonstrate that real improvements of environmental performance can be achieved and the indicators that were utilized have values that are comparable with those published for “advanced” processes practiced in EU.     

絮凝法处理制革工业废水

本文对聚丙烯酰胺絮凝剂进行了筛选。对影响絮凝效果的ｐＨ值，絮凝剂的用量，絮凝剂分子量，无机絮凝剂的用量等诸因素进行了讨论。确定了处理制革废水的最佳条件，处理结果达到了国家排放标准，并且利用复配絮凝剂的处理效果与国外同类产品相当。     

工业污染防治主要措施回顾性评价

随着经济和社会高速发展,工业污染控日趋严重,工业污染物排放量处于较高水平,在一些地区大大超过环境承栽能力。要综合解决目前中国在发展中面临的资源浪费和环境污染等比较突出的问题,唯一出路就是建立资源节约型工业生产体系,走新型工业化道路,这是实现中国经济可持续发展战略的关键所在。污染防治措施回顾评价的基本目的,是通过对各省市工业经济生产状况的调查和分析,评价工业污染防治措施实施的效果,并提出改善污染防治措施的建议,以期防治污染和其他公害,保护和改善生活环境与生态环境,保障人体健康,促进经济、社会的可持续发展。