This study concentrated on the physico-chemical characterization of effluents of leather industry and their reduction by filtration and coagulation processes as physical and chemical treatment. It was observed that the pH was basic and the TSS, TDS, BOD 5 and COD were very high in the case of raw effluent. By adopting settling and filtration through glass wool, the effluents were somewhat treated. After that, chemical treatments were imposed upon them by using different doses of FeCl 3 as coagulant and trimethyl ammonium chloride [(CH 3 ) 3 NHCl] as coagulant aid. It was observed that best result was found by using coagulant (FeCl 3 ) of 120 mg/L dose and coagulant aid [(CH 3 ) 3 NHCl] 12 mg/L dose near the neutral pH. So, it could be said that tannery effluents would be treated by following a combination process of settling, filtering and coagulating with FeCl 3 and [(CH 3 ) 3 NHCl].samples, was measured according to the method of DIN 38409. Again BOD 5 , a method based on oxidation of organic matter by suitable microorganism during a 5 days period was measured according to OXITOP measuring method. The total suspended solid (TSS) and total dissolved solid (TDS) were measured according to the methods of SLC-114 [9] and ASTM D 5907 respectively. Results and DiscussionThe collected tannery effluents were analyzed for determining the parameters named pH, TSS, TDS, COD and BOD 5 . These parameters were measured and found as deviated from the standards. Most metals get soluble in water at low pH [10]. High amount of dissolved solid elements obstructs the density of water. Thus, it generates impact on osmoregulation of water and also lessens solubility of gasses [11]. The parameters of pH, TSS, TDS, COD and BOD 5 were found as 7.6, 5800 mg/L, 10500 mg/L, 4260 mg/L and 820 mg/L respectively in untreated condition. The untreated tannery effluents were settled and then filtered gradually with glass wool and finally treated with Coagulant of Fecl 3 (mg/L) and coagulant aid [(CH 3 ) 3 NHCl].In case of glass wool treatment, the parameters of pH, TSS, TDS, COD and BOD 5 were found as 7.9, 5700 mg/L, 9050 mg/L, 3500 mg/L and 760 mg/L respectively. Here the parameters are better than the previous one. High COD can be for the large amount of inorganic compounds which are not generally influenced by the bacterial corrosion [12]. High level of total suspended solid in water results poor photosynthetic system in the aquatic process and hampers respiratory method of fishes a lot [12]. Again, the effluents were then treated with Coagulant of FeCl 3 (mg/L) and coagulant aid [(CH 3 ) 3 NHCl] dose of (40+4), (80+8) and (120+12) respectively. Table 1 represents the values of the physicochemical parameters named pH, TSS, TDS, COD and BOD 5 of the untreated tannery effluents and after the treatment with glass wool filtration.

Batik is one of the most attractive and precious methods which enhances the value of leather even of a very simple one. Batik is mainly practised on clothes. Practising batik on leather is not yet mainstreamed. In the batik technique on leather, wax is typically used as a colour barrier and then different wax removers are used to remove wax from the leather surface. Wax and wax removers create some complexities in leather. This study aims to explore different techniques such as tie-dye, block, splashing, and painting to create a batik effect on the chrome re-tanned leather surface. Then different colour fastness tests (rub, wash, perspiration, light, and heat fastness) are accomplished to assess the quality of batik leather. The resulting appearance and quality of the finished leathers are assessed with greyscale and found at a satisfactory level. In each fastness test, results in the greyscale ratings are 4/5 to 5. The produced leathers are then used for making coin purses, key cases, and ladies' purses. So, the new batik techniques are recommendable for practice.

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This study investigates to turn the stomach of cow into exotic leather and then leather products that would add value to the end of leather industry. For this purpose, three pieces of cow stomachs are taken to convert into leather through pre-tanning, tanning and post tanning operations i.e. soaking, liming, deliming, bating, pickling, tanning, retanning, dyeing, fatliquoring, finishing etc. Some mechanical operations are also carried out, such as drying and stacking. Several mechanical investigations have been conducted, including tensile strength, stitch tear strength colour rub fastness and shrinkage temperature in order to assess the overall physical properties of prepared leather. Chemical analyses have also been carried out (chromic oxide content, fat content and pH) to find out the quality of leather. It is observed that tensile and stitch tear strengths are much lower than any of the grained upper leather. But the results demonstrate that colour rub fastness is good enough to meet the standard value. Among the different chemical analyses, pH and % of fat content meet the standard value, but chromic oxide content (%) of one sample is below than the standard value of grained upper leather. All these might be due to the prevalence of difference in composition between hide/skin and the stomach of animals. The prepared stomach leather could be used in making of fancy leather goods like key ring, wrist watch belt, hair clip, bracelet etc.

In recent years, the rapid industrialization leads to increase industrial discharges without any appropriate treatment. The present study deals with the removal of Cr (III) ions from aqueous solutions by ZnCl2 treated biochar produced from vegetable tanned leather shaving dust. Effect of various process parameters like solution pH, adsorbent dose, adsorbent type, initial Cr (III) concentration and temperature have been studied in batch system. The thermal resistivity and scanning electron microscopy (SEM) analysis were engaged to perceive the surface morphologies of chemically treated and untreated biochar adsorbent. The experimental data was fitted well to the Langmuir adsorption isotherm model and the adsorption efficiency of chromium (III) was found to be maximum (70%) at low values of pH (around 3) for 0.75 g/50 mL dose of ZnCl2 treated biochar adsorbent. The model matrix of 24 full factorial design approach has been applied at a 95% confidence level to find the impact of different variables on removal Cr(III) ions from waste water. This study revealed that three main factors: Adsorbent type (p < 0.0001; 66.39%), pH (p < 0.001; 16.01%) and adsorbent dose (p = 0.032; 12.15%) have significant impact on Cr (III) ions removal efficiency. For using ZnCl2 biochar, Cr(III) ions removal efficiency was increased 66.39% compared to using untreated biochar. Subsequently, two interaction factors: pH-time and adsorbent type-time (α = 0.05, p < 0.05) have shown statistically significant on Cr(III) ions removal efficiency. The ZnCl2 treated biochar adsorbent prepared from vegetable tanned leather shaving dust is efficient and it is proposed that it can be conveniently employed as a low cost alternative in the treatment of industrial waste water.