Chrome Liquor Research Articles

Sustainable cleaner production technologies and treatment of segregated effluent streams with recovery of quality salt, chromium & water

Conventional process and treatment system adopted by Indian and Global Tanneries consist of Segregation of Spent Chrome Stream and discharge of supernatant for combined treatment along with effluent from all sectional operations starting from soaking to finishing, Conventional physiochemical and biological treatment for reduction of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), etc., Ultra-filtration and Reverse Osmosis (RO) system for recovery of water and Multiple Effect Evaporator (MEE) for the evaporation of RO reject stream and generation of mixed salt in case of Zero Liquid Discharge (ZLD) system and Storage of mixed salt recovered from the MEE system for which no viable disposal system is found. Establishment of treatment system for the mixed stream results in poor performance of biological treatment units, increases the Operation & Maintenance (O&M) cost and accumulation of recovered mixed salt in case of ZLD system. It is estimated that, more than 8-10 tones of mixed salt is generated during the treatment of 1.0 MLD effluent under ZLD system. To address this serious environmental problem, an innovative approach of segregation of saline streams such as soak liquor and chrome liquor are planned to be collected separately with the feasibility of recovering reusable quality salt and chromium in the form cake for regeneration and use in the form of Basic Chromium Sulphate (BCS) by the tanneries. This innovative treatment concept has been developed and is being implemented in many Common Effluent Treatment Plants (CETPs) in India. This will become the first of its kind in Global Leather World. This developmental scheme is in accordance with the guidelines and recommendations of UNIDO in terms of sustainability of ZLD system for leather sector. The technological developments on cleaner productions, centralized chrome recovery reuse system, segregation of saline soak water for separate treatment with recovery of water and quality salt are dealt in this technical paper.

Adsorptive Potential of Acid Modified Moringa Oleifera Wastes for Tannery Effluent Decontamination

Removal of chromium from tannery effluent was carried out using low-cost adsorbents derived from Moringa oleifera seed shells and pods adsorbents. The precursor was modified using acid (H2 SO4 ) impregnation method and characterized using CHNO/S elemental analyzer, FT-IR, SEM, TEM and PXRD. Physicochemical study of the tannery effluent was carried out and documented. Result shows that most physico-chemical parameters investigated for the effluent are above the permissible limit outlined by WHO. Initial concentration of the pollutant, Chromium (987 mg/L) exceeds WHO limit. The maximum adsorption capacity of AMMOS was found to be 137.4 mg/g and that of AMMOP was 277.3 mg/g for chromium removal. Column adsorption study was used to study the effect of experimental variables (pH, initial adsorbate concentration, contact time, adsorbent dosage and temperature), while RE% of Cr by the adsorbents was calculated and recorded for all experimental runs. The equilibrium study for the sorption of Cr was investigated using the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm model. The linearity of the respective models include: Langmuir (R2 of 0.271 for AMMOP and 0.7661 for AMMOS), Freundlich R2 values for AMMOS (0.8337) and AMMOP (0.6485) thus, presenting the Freundlich model as the most applicable isotherm model. Temkin and Dubinin-Radushkevich isotherm models gave poor fittings for Cr on the adsorbents. The rate and mode of diffusion is best explained using the Pseudo-second order kinetic and film diffusion respectively suggesting that the kinetics of the sorption process is controlled by diffusion through the liquid film surrounding the solid sorbent. The efficiency in remediation of effluent using the adsorbents as compared with commercial activated carbon at 95% confidence interval shows that there is no significant difference. This implied that the used of Moringa oleifera seed shells and pods for adsorbents is an economically viable approach to combat remediation challenges in the removal of Chromium from Tan chrome liquor.

The design of industrial symbiosis: an input–output approach

Industrial symbiosis (IS) has gained more attention in the production economics as the pressure on companies increases for the reduction of waste emissions and primary resources consumption. In fact, this has forced companies to provide other companies their wastes as primary resources and vice-versa. These supply circles lead to IS that can mitigate environmental impacts and costs in industrial areas (IA).The aim of this paper is to provide guidelines for the future evolution of IA operating on the basis of IS principles. Given a production network within an IA, perfect IS within the network is defined as a theoretical optimum for IS design where no primary resources is needed from outside and no wastes are discharged outside. Adopting an enterprise input–output approach, the conditions for a perfect IS are found for one-waste and multi-waste cases, and the distance between the states of the actual network and of the related perfect IS is measured.Proposed approach is empirically applied to Santa Croce sull’Arno industrial district of tannery where the recycling of chrome liquors, fleshing, and wastewater are investigated. Results show under which conditions perfect symbiosis is achievable for two waste types. Policy implications are also suggested for the design of IA when IS principles are adopted.

Simultaneously Recovering High-Purity Chromium and Removing Organic Pollutants from Tannery Effluent

Chromium pollution is a serious issue because of carcinogenic toxicities of the pollutants and low recovery rate of chromium because of the presence of organic, such as protein and fat. In this work, high recovery rate and high purity of the chromium ion were successfully prepared by the way of acid enzyme, flocculant, and Fenton oxidation. The experiments were characterized by TG, TOC, UV-VIS, and SEM. In the work, the tannery waste chrome liquor was used as experimental material. The results showed that the percentage of reduction of TOC in the tannery waste chrome liquor by method of Fenton oxidation, acid enzyme, and the flocculant was 71.15%, 65.26%, and 22.05%, respectively. Therefore, the organism content of chrome tanning waste liquid was greatly reduced through the pretreatment. And the application experiment showed that the properties and grain surface and fibers of the tanned leather with commercial chromium powder and chrome tanning agent prepared from the chromium waste liquid treated with Fenton are nearly the same.

Green environment suffers by discharging of high-chromium-containing wastewater from the tanneries at Hazaribagh, Bangladesh

Application of chromium and discharging of high-chromium-containing wastewater is a major concern in leather processing. In tanning process, animal hide/skin collagen is stabilized against biodegradability mostly with basic chromium sulfate. Subsequently in chrome tanning, a fraction of chromium remains in the tan liquor, which is discharged in the waste steam. The study focused on the characterization of discharged chromium-containing wastewater from the tanneries. Results indicate that high concentration of chromium ranging from 2656 to 5420 mg/L was discharged as wastewater after wet-blue production. The physical parameter of spent chrome liquor: total solids (TS) were extremely high. The chemical parameter such as pH (2.4–3.0) was highly acidic. A fraction of discharged spent chrome liquor is directly mixed with the water of the River Buriganga, which causes serious environmental pollution; another fraction of chromium is settled out in the lagoon or adsorbed by sediment/soil. It is suspected that the adsorbed chromium could be eluted to groundwater in the tannery area, which could be a great threat in the near future. Practicing chromium recovery and reuse systems might be a good approach to make leather production environmental friendly, and consequently Bangladesh could save huge amounts of chemical costs.

Phytotoxic effect of chrome liquor on growth and chlorophyll content of Spirodela polyrrhiza L. Schleid

The present study assessed the tolerance of Spirodela polyrrhiza (L.) Schleid (giant duckweed) exposed to different concentrations (5% -100%) of chrome liquor for 7 days. Physiological conditions of S.polyrrhizaplants were monitored daily by measuring fresh weight and chlorophyll-a and chlorophyll-b. Fresh biomass of Spirodela plant showed concentration and duration dependent reduction with minimum value (5.71 g) reported on 7 d at 100% tannery effluent concentration. Likewise, significant reduction in chlorophyll-a and chlorophyll-b content wasobserved in concentration-duration dependent manner with maximum reduction reported to be 99.8% and 99.6% respectively on 7 d at 100% effluent concentration in comparison to control.

Bioremediation of Tannery Effluents Using a Consortium of Blue-Green Algal Species

Trivalent chromium in the form of basic chromium sulfate (BCS) is used for tanning hides/skins and is a strong pollutant of the soil and water bodies. Significant quantities of unutilized chemicals, such as sulfates, chlorides, are also discharged, contributing to high levels of total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), etc. Though many treatment techniques are being practiced, biotechnological methods are gaining importance. Biosorption is recognized as a cost-effective technology worldwide; one potential sorbent being blue–green algae (BGA), for treating metal-bearing effluents. This work studies the feasibility of using a species each of Spirulina, Oscillatoria, and Synechocystis, individually and as a consortium, as sorbents to remove Cr3+ from a segregated stream, viz. exhaust chrome liquor (ECL) and synthetic BCS solution. The species studied were found to be effective in removing Cr3+ considerably at varying concentrations, besides reducing sulfates, BOD, COD, etc. The results of ECL experiments were more encouraging than those for BCS solution. The kinetic data on Cr3+ sorption onto algal biomass fit well into the pseudo-second order model. The equilibrium data were analyzed using the classic Langmuir and Freundlich isotherm models, yielding good fits. The results of the experiments indicate that algal consortia could be good alternatives to the conventional treatment methods for leather and other industrial wastewaters containing chromium.

Biosorption of trivalent chromium by free and immobilized blue green algae: Kinetics and equilibrium studies

The process of biosorption of trivalent chromium (Cr3 +) by live culture of Spirulina platensis and the sorption potential by the dried biomass, in both free and immobilized states have been investigated for a simulated chrome liquor in the concentration range of 100–4500 ppm. Both live and dried biomass were very good biosorbents as they could remove high amounts of chromium from tannery wastewater. Polyurethane foam and sodium alginate were used as immobilizing agents and their performances compared. Biosorption kinetic data on Cr3 + sorption onto dried biomass were analyzed using pseudo–first-and pseudo–second-order kinetic models in batch column experiments. The second-order equation was more appropriate to predict the rate of biosorption. Subsequently, the effects of height of packing & diameter of the column, concentration of blue-green algae (BGA) in varying amounts of sodium alginate, chromium concentration were studied. The results fit into both Langmuir & Freundlich isotherm models with very high regression coefficients. Furthermore, equilibrium studies using retan chrome liquor (RCL), with a chromium concentration of 1660 ppm, obtained from a tannery also showed promising results. In general, our studies indicate the efficacy of the algal species in removal of chromium from tannery wastewater.

Bioabsorption of chromium from retan chrome liquor by cyanobacteria

The bioaccumulation of chromium from retan chrome liquor by Spirulina fusiformis was investigated under laboratory as well as field conditions. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 300mg/l. The effect on various physico-chemical parameters like total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), chlorides, sulphates, phenols, biochemical oxygen demand (BOD) and chemical oxygen demand (COD) and biochemical studies related to biomass, chlorophyll-a and protein were also carried out. The present study indicates that S. fusiformis is very effective in removal of chromium (93-99%) besides removing other toxicants from retan chrome liquor. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and FTIR studies indicate the interaction/complexation between Cr and alga. The mechanism involved in bioaccumulation of chromium is also discussed. The process when upgraded can be applied for detoxification of tannery effluents.

Bioaccumulation and biosorption of chromium by Aspergillus niger MTCC 2594

Chromium toxicity is of prime concern due to chrome tanning processes in the leather sector. Chrome tanning results in the discharge of toxic levels of chromium causing pollution hazards. Chromium levels of Cr(III) and Cr(VI) were high above permissible limits in chrome samples after chrome tanning. The potential of Aspergillus niger MTCC 2594 to accumulate chromium as well as its biosorption capacity is investigated in this study. Bioaccumulation of Cr(III) and Cr(VI) in the spent chrome liquor has resulted in a 75-78% reduction of the initial Cr content in 24-36 h. A. niger biomass is found to be very effective in the biosorption of Cr(III) and Cr(VI) in spent chrome liquor. Maximum adsorption of 83% for biosorption of Cr(III) at 48 h and 79% of Cr(VI) at 36 h in spent chrome liquor is observed. The biosorption characteristics fit well with Langmuir and Freundlich isotherms and the adsorption parameters are evaluated. The biosorption of Cr also follows Lagergren kinetics. A. niger biomass is effectively used for the biosorption of chromium with 79-83% Cr removal in 36-48 h.

Techno-economic evaluation of membrane filtration for the recovery and re-use of tanning chemicals

The majority of pollution generated from leather manufacturing can be contributed to the inefficiency of chemical use in leather processing and to organic substances derived from the hides during processing. In particular, the overall tanning processes performed in drums can be characterized by a high consumption of water and chemicals, most of which are found in the final wastewater. To ensure full penetration and reaction of chemicals with collagen, chemicals are added in excess and are only partly up-taken by the leather. Significant savings of chemicals can be achieved by recovery and recycling of chemicals and water from part streams, thus reducing environmental impacts. This research formed an integrated approach to investigate and exploit the potential of a closed loop operation for various part streams of tanneries. Each of the process streams was separately collected, treated and purified by membrane technologies to obtain a recyclable liquor which can be re-used operationally. In this way a complete recovery of process liquors can be achieved for immediate operational re-use. Membrane technology has been applied to recover chemicals from un-hairing, vegetable tanning, chrome liquors and to polish saline part streams for re-use. By applying membrane filtration up to 90% of the treated liquors can be recovered giving a remaining concentrate volume of only 10%. The permeate obtained from several process areas contained to a high extent chemicals, which were re-used for leather processing.

Recovery of Cr(III) from Tannery Spent Chrome Liquor for Reuse

This paper embodies details on the extraction behavior of Cr(III) along with Al(III), Fe(III), Mg(II), Mn(II), Co(II), Ni(II), and Cu(II) from hydrochloric acid media employing the Cyanex 301-toluene system. All of these metals, except Cr(III), Mg(II), and Mn(II), are extracted into the organic phase. This property of the extractant has been used to separate Cr(III) from the binary mixtures. The partition data have been extended onto spent chrome liquor, and this waste has been treated in such a manner so that it becomes suitable for use in trivalent plating baths. The hydrolytic stability and recycling capacity has been reported. Because the concentration of Cr(III) in the waste is much lower than that required for chromium depositions in Cr(III) plating baths, a concentration step using MgO as a precipitating agent has been appended. To summarize, this paper envisages a new approach to tannery waste management that focuses on treating spent chrome liquors using a solvent extraction technique in such a manner that the waste becomes suitable for use in trivalent plating baths. This would not only help abate pollution but also recover the metal in a pure form.

Mono(2-ethylhexyl) Phosphoric Acid as an Extractant for Cr(III) and Its Application to Industrial Waste

The paper contains details on the extraction behavior of Cr(III) along with Fe(III), Mg(II), Mn(II), Co(II), Ni(II), and Cu(II) from hydrochloric acid media employing the mono(2-ethylhexyl) phosphoric acid (H2MEHP–n-hexane system. The effects of various parameters, such as the concentrations of acid, metal ion, and extractant, and the nature of diluent, on the extraction of Cr(III) have been investigated. The data suggest that up to 90% Cr(III) can be extracted in the 5 × 10−3 to 0.1 M acid range. The extractant can hold the metal ion up to one-tenth of its molar concentration. The extracting species in Cr(HR)a, where H2R is H2MEHP. The partition data have been used for binary separations of Cr(III) from some commonly associated metal ions. The practical utility of the extractant has been demonstrated by recovering Cr(III) from spent Fe-Cr catalyst and spent chrome liquor.

Chrome tannage using high-intensity ultrasonic field

The process time in chrome tannage in leather making, using an elastic compression cycle followed by irradiation by high-intensity ultrasound, is quite short lasting only a few minutes, compared with a process time of several hours in modern chrome tannage. After ultrasonic irradiation, samples were basified in 17 h in chrome liquor at a pH of 4.0 and the shrinkage temperature was measured. The determination of the efficiency for the chrome liquor penetrating into the hides can be based on the steepness of the shrinkage temperature-processing time curve. An approximate value of 20°C min −1 can be evaluated for the initial slope of the curve when elastic compression and high-intensity ultrasonic irradiation is used, and a processing time of 2 min is required in chrome liquor (plus 17 h basification and 24 h storage time) to obtain leather stable to boiling. Usually, hides are kept in chrome liquor for 2 h.

Isolation and characterization of chromium-resistant bacteria from tannery effluents.

Chromium (Cr), a transition metal, is one of the major sources of environmental pollution. It is discharged into the environment through the disposal of wastes from industries like leather tanning, metallurgical and metal finishing, textiles and ceramics, pigment and wood preservatives, photographic sensitizer manufacturing, etc. In the environment chromium occurs mainly in trivalent and hexavalent forms. The hexavalent chromium (Cr{sup 6+}) compounds are comparatively much more toxic than those of trivalent chromium (Cr{sup 3+}). The reason for such toxicity appears to be due to its rapid permeability through biological membranes and subsequent interaction with intracellular proteins and nucleic acids. The tanning industry, which commonly utilizes {open_quotes}chrome liquor{close_quotes} in the tanning process, discharges the effluents into the environment containing chrome salts in excess of the maximum permissible limits. Sludge deposition from such effluents, therefore, provides a natural environment for enrichment of chromium-resistant bacteria. Chromium-resistant microorganisms from such chromium-contaminated sediments have been isolated by several investigators. The present study was an attempt to evaluate the status of chromium-resistant bacteria in the tannery effluent sediments of Calcutta-based tanning industries. 14 refs., 2 figs., 6 tabs.

Utilization of spent chrome liquor

Abstract Chrome tanning is widely used in the local tanneries. A considerable amount of chrome is normally left in the exhaust liquor. The primary aim of this paper is to investigate the possibiilty of utilizing the spent solution or recovering the chrome by other techniques which will help greatly in improving the economy of the process and will also reduce the chrome content in the effluent. An experimental investigation has been carried out applying different techniques for the recovery of the chrome salt namely by (a) precipitation techniques by suitable alkili (b) recovery by cationic exchange resin and (c) recycling of the spent liquor for reuse in chrome tannage. The experimental results revealed that the recycling process is most economical and easy to apply with respect to the conditions undertaken.

有機還元剤によるクロム液の鞣皮性に関する研究

有機還元剤によるクロム液の鞣皮性に関する研究

PRODUCTS and PROCESSES: PROVIDING INDUSTRY WITH THE MEANS TO COMBAT CORROSION

Waste Chrome Liquors Disposal. A new service for the disposal of waste chrome plating liquors has been started by Associated Chemical Cos. Ltd. for users of the companies' products. It enables customers to dispose of their waste chromic acid liquors down to 25% CrO3 w./w. and, in certain circumstances, liquors of even lower concentrations, by delivering to a bulk store in the company's Birmingham works. It may be possible in some circumstances to make token payments for liquors over 30% CrO3 w./w.

有機還元剤によるクロム液の鞣皮性に関する研究

SO2還元液に有機酸塩を加えた場合,クロム塩の皮粉との結合力におよぼす影響を試験するために,義酸ソーダ,修酸ソーダを加えたSO2還元液およびグルコース還元液の各0.5%Cr液40mlを用い,NaClO4 HClO4混合液で処理した皮粉2gを4時間振盪し,これらの鞣皮粉について,水によつて離脱する結合クロム分を定量した.さらに,吸着クロムの荷電分布およびメチル化皮粉を用いて,離脱クロムを荷電別に検討した.得られた結果は,つぎの通りであつた.1. クロム液に有機酸塩を加えると,その鞣皮粉には水で離脱される結合力の弱いクロム量が増加した.2. 水によつて離脱した結合クロム量と,吸着クロム中のマスグ化したアニオンクロム量とは,ほとんど等しかつた.2. しがしメチル化皮粉を用いて試験した結果では,吸着したアニオンクロムおよびカチオソクロムの一部はいずれも水によつて離脱した.またそれぞれの離脱量は,有機酸塩をクロム液に加えた場合に増加した.

有機還元剤によるクロム液の鞣皮性に関する研究

皮粉によるクロムの吸着性に及ぼす有機酸基の影響を試験するために,予備的に,全クロム吸着量および陰陽両荷電クロムの吸着量に及ぼすpHと鞣製時間(1および4時間)の影響を,グルコース還元液を用いて試験した.ついでSO2還元液に,酢酸ソーダ,修酸ソーダ,酒石酸ソーダおよびクエン酸ソーダを加えて熟成し,グルコース還元液とほぼ同量のマスク化クロムを生成させた供試鞣液を用意した.それらと,義酸ソーダ添加SO2還元液,SO2還元液およびグルコース還元液,計7種の供試液を用いて,あらかじめpHを4.0,Cr濃度を0.5%に調整した各液40ccで,処理皮粉2gを4時間振盪,鞣製した.鞣製前後のクロム液についてイオン交換分析を行ない,荷電の異なるクロム塩の吸着量を算出し,特にアニオン•クロムの利用率から,クロム塩の吸着性に及ぼす配位有機酸基の影響について検した結果を取りまとめると,次のとおりである.1. 全クロム吸着量は,pH4.0で鞣製した場合が最も多かつた.アニオン•クロムは鞣製pHが低いほど,またカチオン•クロムはpHが高いほど,多く吸着された.2. アニオン•クロムは鞣製開始後,優先的に吸着された.3. 全クロム吸着量は,有機酸塩の種類と量によつて変わるが,一般に有機酸塩を加えると,カチオンクムの吸着は阻害されて,全クロム吸着量中アニオン•クロムの占める比率が高くなつた.4. カチオン•クロムの吸着利用率は,有機酸塩によつて低下する傾向を示した.5. アニオン•クロムでは,有機酸基の配位によつて,吸着性に顯著な変化を示さなかつた.またアルカリに対する安定性の異なるクロム塩の利用率も,ほとんど変わらなかつた.