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.     

Ultrasound-accelerated enzymatic hydrolysis of solid leather waste

The leather industry is a heavy pollution industry and looking for clean technology. The utilization of enzyme and ultrasound in the industry are potential eco-friendly technologies.Enzymes can degrade the untanned solid leather waste. According to our investigation, ultrasound (40 kHz, 0.64 W/cm²) has little effect on the activity of one alkaline protease from Bacillus licheniformis. It is the first time to use ultrasound to accelerate the enzymatic hydrolysis of the untanned solid leather waste. With the application of ultrasound, the value of k_A for the enzymatic hydrolysis of the untanned solid leather waste increases 18% and K_M is almost unchanged, compared with that obtained without ultrasound. Ultrasound improves the ultimate conversion ratio from 57.6% to 84.1%. The reason is that ultrasound can facilitate the protease through the pores of skin and impair the integrity of collagen. Amino acid analysis indicated that ultrasound can promote the breakdown of helical regions of collagen which are difficult to attack by proteases.In view of environment protection, the use of enzyme and ultrasound in combination is a promising clean technology for the disposal of the untanned solid leather waste.     

浙江省合成革行业挥发性有机物污染特征及排放系数

以2015年浙江省175家合成革企业调研数据为基础,分析当前浙江省合成革行业挥发性有机物(VOCs)污染治理情况,通过研究筛选出161家重点企业,分析合成革行业污染基本排放特征并计算其VOCs排放系数.结果表明,绝大部分企业对废气采取治理措施,但聚氨酯(PU)后处理工艺没有废气收集和处理设施;绝大部分企业使用的是溶剂型原辅材料,废气中VOCs的主要污染因子为二甲基甲酰胺(DMF)、甲苯、乙酸甲酯、丙酮、乙酸乙酯和丁酮等物质;全省合成革行业的VOCs排放系数均值为0. 168 kg·m~(-2).其中聚氨酯平均排放系数0. 170 kg·m~(-2),聚氯乙烯(PVC)排放系数为0. 142 kg·m~(-2);聚氨酯湿法工艺排放系数均值为0. 191 kg·m~(-2),聚氨酯干法工艺VOCs排放系数均值为0. 179 kg·m~(-2),聚氨酯后处理工艺VOCs排放系数均值为0. 120 kg·m~(-2).     

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.     

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.     

Ecological utilization of leather tannery waste with circular economy model

Circular economy (CE) focuses on resource-productivity and eco-efficiency improvement in a comprehensive way, especially on the industrial structure optimization of new technology development and application, equipment renewal and management renovation. The leather industry on the one side boosts the local economic development, on the other side however leads to the tremendous environment pollution and biological chains destruction. The CE model has been implemented as a new way of raw materials, water and energy consumption reduction in the leather industry. Reduce, Reuse, Recycle and Recover of the tannery effluents have been discussed in detail according to the different operation processes. The successful treatment approaches with analysis in the aspects such as wastewater, solid waste, sulfide, Chemical Oxygen Demand (COD), ammonium salt, chloride and chrome of the leather tannery with CE model provide guidance for the sustainable development of leather industry in the future.     

海河流域主要污染物排放强度及其源结构解析——以2007年为例

以海河流域污染源普查数据为基础,通过污染物排放量、排放密度和排放行业结构分析,系统解析流域污染源结构.结果表明,流域废污水来源复杂,污染物排放空间差异显著,工业行业结构性污染突出.流域北部废污水排放以生活污水为主,南部以工业废水为主,COD排放以工业源为主.污染物排放空间格局上,COD排放主要集中在北三河、子牙河及徒骇马颊河水系;氨氮排放在子牙河水系高度集中;重金属、氰化物、挥发酚仅在局部区域集中排放.污染物行业结构上,造纸、食品和石化是COD主要排放行业,占排放总量75%;石化、食品和皮革是氨氮排放主要行业,占排放总量80%;重金属主要排放行业为石化、皮革和冶金.根据污染物排放强度分布和排放结构,子牙河水系是海河流域污染治理重点区域,造纸、食品和石化行业是污染负荷削减重点行业.     

Material flows in the life cycle of leather

This paper presents a study on the resource and environmental profile of leather for communicating to the consumers about the environmental burdens of leather products. The results indicate that significant environmental impacts were caused during the tanning and finishing of leather as well as the electricity production and transportation required in the life cycle. The use of fossil fuels in the production of energy has greater impact with increased emissions leading to about 15190 kg CO₂ equivalent of global warming and about 73 kg SO₂ equivalent of acidification while producing 100 m² of leather for shoe uppers. Further resource use of 174 kg of coal, 6.5 kg of fuel oil, 17.4 m³ of water and 348 kg of chemicals of which about 204 kg are hazardous are consumed, and wastewater of about 17 m³, BOD of 55 kg, COD of about 146 kg, TDS of 732 kg and solid waste of about 1445 kg are generated during the life cycle for the production of 100 m² of leather. The total solid waste generated is 1317 kg, out of which about 80% is biodegradable contributed by slaughtering, tanning and finishing stage, 14% is non-biodegradable contributed by tanning, finishing and electricity production stages and 6% is hazardous mainly from tanning and finishing stage of leather.     

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.     

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。     

Research on the degradation mechanism of pyridine in drinking water by dielectric barrier discharge

Pyridine, an important chemical raw material, is widely used in industry, for example in textiles,leather, printing, dyeing, etc. In this research, a dielectric barrier discharge(DBD) system was developed to remove pyridine, as a representative type of nitrogen heterocyclic compound in drinking water. First, the influence of the active species inhibitors tertiary butanol alcohol(TBA),HCO_3~-, and CO_3~(2-)on the degradation rate of pyridine was investigated to verify the existence of active species produced by the strong ionization discharge in the system. The intermediate and final products generated in the degradation process of pyridine were confirmed and analyzed through a series of analytical techniques, including liquid chromatography–mass spectrometry(LC–MS), high performance liquid chromatography(HPLC), ion chromatography(IC), total organic carbon(TOC) analysis, ultraviolet(UV) spectroscopy, etc. The results showed that the degradation of pyridine was mainly due to the strong oxidizing power of ozone and hydroxyl radical produced by the DBD system. Several intermediate products including 3-hydroxyl pyridine, fumaric acid, 2, 3-dihydroxypyridine, and oxalic acid were detected. Nitrogen was removed from the pyridine molecule to form nitrate. Through analysis of the degradation mechanism of pyridine, the oxidation pathway was deduced. The study provided a theoretical and experimental basis for the application of DBD strong ionization discharge in treatment of nitrogen heterocyclic compounds in drinking water.     

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。     

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。     

1990-2018年浙江省人为铅排放时空变化解析

随着工农业的高速发展,大量的人为铅排放到环境,引起了一系列的生态健康问题.本文以工农业集产区浙江省为案例,系统构建了18个铅排放源排放清单,其中新增添了纺织业、制革业、造纸业、秸秆利用、牲畜废物利用、化肥消费、农药消费等铅排放行业,估算了浙江省1990—2018年各污染源铅排放量,分析了其时空变异趋势.结果表明,浙江省前期（1990—2000）铅排放通量增长有限,其排放量仅约2500 t·a^-1,有色金属开采贡献了约55%;其后增长速度较快,到2014年以后达到较高的稳定值,约35000 t·a^-1,是1990年的14倍,铅酸蓄电池生产是其主要排放源,占比从14%增长到了80%.从排放的去向来看,98%左右的铅通过固废的形式进入环境,而进入大气和废水的只有2%和0.2%左右,其主要排放源分别为铅酸蓄电池生产、原煤燃烧、纺织业.而浙江省各个地区铅排放表现出较大的空间差异,各地区因工农业发展模式不一样,人为排放源也不一样.总体来看北部高于南部,尤其湖州、绍兴、舟山等地铅排放量较高.可见,浙江省人为铅排放形势仍然很严峻,控制好铅酸蓄电池生产固废资源化无害化处理是源头控制的重中之重,调整原煤燃烧将有利于降低大气铅排放,纺织业废水净化处理对缓解水体铅污染有重要意义.本研究不仅为浙江省铅污染治理提供了重要科学依据,同时也为铅污染源端防控提供了数据基础.     

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.     

Cleaner beam house processes trial on cattle sofa leather

Leather processing has been an important light industry in China, which has contributed a lot to economy. The recent environmental challenges caused tremendous pressure to leather manufacture. The conventional beam house processes employ a wide range of chemicals which result in more than 60% of the total pollution in leather processing (mainly based on COD, BOD, TS, SS, NH₃–N). In this study, cleaner beam house processes were tested on cattle sofa leather to provide a clean environment. A control experiment was run parallel using conventional beam house processes. The results show that the de-hairing is complete through pelt histological microstructure, the extent of opening up of fibre bundles is very good, which is substantiated through chrome distribution analysis, scanning electron microscopic pictures of wet blue leathers and the analysis of contents of total proteins, polysaccharide and hydroxyproline in composite liquor, and the performance of the leathers is shown to be satisfied with the quality standard of sofa leather. The results from composite water analysis show that the cleaner processes enjoy in the reduction of emission water, chemical oxygen demand, total solids and ammonia-nitrogen loads by 46%, 93%, 58% and 54%, respectively, compared to the conventional processes. The total dry sludge from the clean processes is almost eliminated, and the composite cost is decreased by 10%.     

Reclamation treatment of the chrome leather scrap

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浙江省木制品行业挥发性有机物排放特征及排放系数

以2015年310家木制品企业调查数据为基础,分析当前浙江木制品行业VOCs污染治理情况,并筛选出213家重点企业,分析木制品行业污染特征并计算VOCs排放系数.结果表明,浙江94%以上的木制品企业未能有效处理VOCs,且大部分企业仍使用溶剂型原辅材料,主要污染因子为二甲苯、乙酸丁酯、乙酸乙酯、甲苯、甲醛等9种VOCs.全省木制品行业VOCs排放系数为9.34 kg·(万元)~(-1),其中胶粘工艺排放系数为0.95 kg·(万元)~(-1),涂装工艺为9.36 kg·(万元)~(-1);涂装为主要污染工段,其中水性(UV)涂料使用企业排放系数为3.10 kg·(万元)~(-1),溶剂型涂料企业中,木质家具生产企业排放系数高达16.85 kg·(万元)~(-1).     

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.     

膜生物反应器处理工业废水中膜污染及膜过滤特性研究

采用膜生物反应器(MBR)中试试验装置处理制革、印染工业园区混合废水,考察了悬浮污泥浓度(MLSS)、溶解性微生物产物(SMP)和松散型胞外聚合物(EPS)表征总量、胶体粒子等因素对膜污染发生的影响程度.结果表明,试验装置启动后的120 d内,发生轻度膜污染现象,过滤膜阻力R20从1.5×1012m-1增加至1.8×1012m-1.MBR池内胶体粒子浓度与膜过滤阻力变化呈现明显的线性相关,而MLSS、SMP和EPS表征总量等因素的变化与膜过滤阻力的变化不存在相关性.分析认为胶体粒子是引起该试验装置发生膜污染现象的主要因素,其成因可能是胶体粒子通过附着在膜表面,沉积堵塞膜孔,从而造成膜污染.