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RO membrane removal of unreacted chromium from spent tanning effluent. A pilot-scale study, Part 2
Abstract
In chromium tanning process, about 20–40% of applied chromium is usually discharged into sewerage system causing serious environmental impact. The spent chromium effluents collected from two local small-size tanneries indicated that chromium concentration ranged from 1300–2500 mg Cr6+/l, while NaCl concentration varies from 40000 to 50000 mg/l. The study of chromium removal efficiency by using of a pilot-scale setup of 7 and 16 bar RO membrane units at different working pressures and under variable salt concentrations were carried out to remove the hazardous chromium from the spent tanning effluent and recover it for further recycling. The study proved that the membrane technique is able to separate chromium efficiently from the pretreated tanning wastewater. The low-cost RO membrane units, i.e. the medium and low pressure, could be used economically for separation and recovery of chromium from wastewater of small-size tanning shops.
... Наиболее часто используемые методы удаления Cr 6+ из сточных вод включают восстановление [17,18], осаждение [19], мембранную фильтрацию [20], биоредукцию и биосорбцию [21][22][23][24], ионный обмен [25] и адсорбцию [26][27][28][29][30][31]. ...
... В процессе хромового дубления от 20 до 40% используемого хрома обычно попадает в сбросовые воды и оказывает вредное воздействие на окружающую среду [20]. Анализ отработанных хромовых стоков показал, что концентрация хрома находится в пределах 1300-2500 мг Cr 6+ /л. ...
The article considers sources of hexavalent chromium in the environment, its toxicity, methods of removal, main adsorbents used for Cr(VI) removal, obtaining of carbon sorbents using different raw materials. The interpretation of the mechanism of Cr(VI) removal is given. Chromium is widely used in many industries, which results in the generation of a large amount of hazardous waste - wastewater from steel, metalworking, electroplating, tanning, automotive, paint, paper-pulp and textile plants. Chromium is one of the most dangerous inorganic pollutants because of its carcinogenic effects on biological species. In aquatic environments, chromium usually exists in the trivalent Cr(III) or hexavalent Cr(VI) state. Hexavalent chromium ions in aqueous media are highly toxic even in small amounts, and their removal from solution poses a serious wastewater treatment problem. Methods such as adsorption ion exchange, membrane separation, coagulation, chemical precipitation, extraction and electrochemical separation can remove hexavalent chromium from wastewater. Adsorption is considered to be the most efficient, economically feasible, environmentally sustainable and technologically promising process. Among adsorbents of different nature, activated carbon is the most widely used. Wood is the most common source of activated carbon but given the importance of wood in maintaining the ecosystem, alternative sources of activated carbon production are being sought. Activated carbon is produced from various materials by high temperature carbonization. Activated carbon materials have high specific surface area and developed porous structure. The micropores in activated carbon account for the physical adsorption of chromium ions. The presence of functional groups containing O and N in activated carbon affects the chemical structure and the process of chemical sorption.
... Tannery wastewaters are characterized by being strongly alkaline with a high oxygen demand and high content of salts and nutrients, one of which is Cr (Bajza and Vrcek, 2001). Nowadays chrome tanning is favoured by the majority of the leather industry because of the speed of processing, low cost, colour of leather and greater stability of the resulting leather (Hafez et al., 2002). However, uptake of the Cr into the leather is not complete and relatively large amounts are found in the effluent. ...
... As treatment of Cr-containing wastewater is expensive, many developing countries employ primary treatment alone which cannot reduce Cr to the level below legal discharge limit (Alves et al., 1993). Advanced processes such as ion exchange, reverse osmosis, electrolysis and chemical precipitation are recommended (Vlyssides and Israilides, 1997;Hafez et al., 2002). However, these methods are expensive and are often not considered cost effective for small sized industries. ...
The objective of the present study was to evaluate the potential use of water hyacinth for the removal of chromium (Cr) from tannery wastewater. This experiment was performed using healthy, young and acclimatized water hyacinth collected from unpolluted Awash River. Cr concentrations of 3, 5, 7, 10 and 20 mg/L were added to five different polyethylene tanks, containing 40 litre tap water cultured with Hoagland's solution. A sixth tank containing Cr-free water was used as a control group. Six plants of equal wet mass (each 12.5 ± 2 g), shoot length (11 ± 2 cm) and root length (6 ± 2 cm) were transferred into each tank and allowed to grow in a greenhouse for 42 days. From each tank plants were harvested randomly every week. Bioaccumulation factor, translocation factor, shoot and root length; wet biomass and dry weight of the shoot and root were measured, and relative growth rate, tolerance index of the root and tolerance index of wet mass were analyzed. The maximum accumulation of 2.52 X 10 3 µg/g of water hyacinth was achieved in the plants exposed to 20 mg/L Cr solution. The root part of the plant accumulated 2.42 to 3.82 times higher than the shoot part. An overall Cr removal efficiency of up to 91% was achieved in this study, but the efficiency decreased as the concentration of Cr in water increased. The growth of the plant was inhibited at high concentration due to Cr toxicity. Therefore, the application of water hyacinth for Cr removal will be sustainable, if the concentration of Cr in wastewater does not exceed about 10 mg/L. The relative growth rate (RGR) of the plant decreased with increasing Cr concentration and the growth was inhibited above 15.3 mg/L Cr in water. Based on the above data, it could be concluded that water hyacinth can potentially be used for the removal of Cr from tannery effluents which is a major environmental problem in Ethiopia. However, further investigation is needed to ascertain the optimum conditions for maximum removal.
... Basic Chromium Sulphate (Cr(OH)SO 4 ) is usually used for chrome tanning step for hide stabilization against microbial degradation. Cr ion concentration in the tannery wastewater were found to be 2500-8000 ppm [2] . Chromium causes the water and soil contamination and indirectly causes the serious health problem and environmental problems [3].However, treatment of tannery chromium-rich effluents by primary treatment systems such as; biological, oxidation or physico-chemical processes still leaves chromium levels in the treated wastewater above the legal discharge limit(0.5mg/l ...
... Whereas the sludge formed by NaOH and Ca(OH)2 are gelatinous and dewatering is also difficult. Here from the data we can see that, the sludge volume produced by MgO is much less than sludge volume produced by Ca(OH) 2 is much easier than sludge with huge volume. As the reaction proceeds, the amount of precipitate increases as small size precipitate gets adhered together and lead to maximum precipitation, sometimes other chemical entities (ions and molecules) also get adhered with precipitate and mass of precipitate increases. ...
This research presents the process of removing chromium as well as color and COD from chrome liquor through chemical precipitation. Initially chromium concentration of sample was 5607ppm. After conducting series of jar tests, residual chromium for 5000mg/l of MgO, NaOH and Ca(OH) 2 was 0.21ppm, 0.76ppm, 5.61ppm respectively and sludge volume ratios were 1:1.26:2.22. For cost efficiency, different combinations of Ca(OH) 2 and others were used. 5:1 ratio of Ca(OH) 2 :NaOH showed better removal & higher cost efficiency.
... The tanning industry generates a significant amount of liquid and solid wastes during leather processing. Chromium compound is the key reagent in leather manufacturing and about 60-70 % of the applied basic chromium sulphate reacts with collagen fibres to create crossconnections between chromium and collagen fibre which stabilizes the leather, the leftover chromium salt is still present in the wastewater and is discharged from the industry without treatment (Hafez et al., 2002). The wastewater from the tanneries may contaminate the groundwater with chromium, endangering the health of those who consume it. ...
... There has been a serious environmental challenge for the produced Cr industries, due to pressures from public opinion and the numerous environmental regulations imposed [5,6]. Various techniques have been employed for recovering or removing Cr from wastewater such as precipitation [7][8]; cementation [9]; coagulation [10] and membrane technologies [20][21][22]. Many adsorption methods have also been investigated using several types of adsorbents such as activated carbon [11], lignin [12], diatomite [13], natural hydrothermal zeolites [14], synthetic zeolites [15], bentonite clay [16], biosolid sorbent from waste-activated sludge [17], biosorption by aquatic weeds [18]; ion-exchange resins [19]. ...
... There has been a serious environmental challenge for the produced Cr industries, due to pressures from public opinion and the numerous environmental regulations imposed [6,7]. Various techniques have been employed for recovering or removing Cr from wastewater such as precipitation and sedimentation [8] cementation [9], coagulation/flocculation [10], adsorption by several types of adsorbents such as activated carbon [11], lignin [12], diatomite [13], natural hydrothermal zeolites [14], synthetic zeolites [15], bentonite clay [16], biosolid sorbent from waste-activated sludge [17], biosorption by aquatic weeds [18], ionexchange resins [19] and membrane technologies [20][21][22]. Most of these methods suffer from some drawbacks such as high capital and operational costs, large input of chemicals, incomplete removal and their operational problems. ...
The aim of this study is to investigate the performance of batch electro coagulation (EC) using iron electrodes with bipolar configuration for simultaneous removal of chromium (Cr 3+) from synthetic wastewater. The influences of current density (from 2 to 25 mA/cm 2), initial metal concentration (from 100 to 250 mg/L) and supporting electrolyte (0-12 mmol/L Na 2 SO 4) on removal efficiency are explored in a batch stirred cell to determine the best experimental conditions. The results indicate that EC was very efficient to remove Cr 3+ from the synthetic wastewater having an initial concentration of 250 mg/L of Cr 3+ under the best experimental conditions. At the current density of 15 mA/cm 2 with a total energy consumption of ∼18.5 kWh/m 3 , more than 98.7% removal value was achieved for Cr 3+ after 20 min EC treatment. Time of 20 minutes EC treatment was chosen as optimum time to gain less than 4 mg Fe/L in the treated water.
... There were diverse technologies applied for the removal of chromium species, including electrochemical process [21,22], membrane filtration [20,[23][24][25], adsorption [15,26,27], precipitation [28][29][30][31], ion exchange [32][33][34], reduction [35], extraction [36][37][38], ferrite process [39], photocatalytic process [40][41][42][43], adsorption coupled reduction [44][45][46][47], coagulation [11,48,49], combined adsorption-membrane process [50], combined coagulation-precipitation process [51], immobilization [52], combined membrane-electrodialysis process [19], combined precipitation-flotation process [53], reduction assisted by oxidant [54] and reversible reduction coupled adsorption [2,55]. Besides, some studies explained chromium removal by certain biological techniques [56]. ...
... However, throughout the tanning process, only 60% of the initial chromium salt concentration is consumed by collagen fibers and permeated into the pickled pelt and 40% of this chromium salt remains unused which are being discharged along with the tannery wastewater [26]. After the manufacturing of wet blue leather, concentrations of chromium species in wastewater might be varied from 2656 to 5420 mg/L [30], 5001 to 5023 mg/L [31], 2500 to 8000 mg/L [32], 2000 to 5000 mg/L [29], 2000 to 5000 mg/L [33], and 3600 mg/L [34]. Every year, 1.5 × 10 4 ton of chromium salt is used in chrome tanning processes in various tannery industries in Bangladesh. ...
Continuous discharge of untreated wastewater with high chromium contents from tanning industries causes severe environmental pollution in different aquatic systems as well as poses a variety of health risks. To reduce harmful chromium pollution in various water bodies, it is imperative to develop a method that is both affordable and environmentally benign. In the present study, chromium was successfully removed from tannery effluents using the roots of the water hyacinth (Eichhornia Crassipes). Chromium status in wastewater bodies before and after the biosorption processes was evaluated using standard spectrophotometric techniques such as UV–Vis and atomic absorption spectroscopy (AAS). The metal removal capacity of water hyacinth roots was determined by varying the biosorbent dosages, temperature, and starting chromium ion concentrations. The maximum removal of chromium was found 95% from dilute tannery wastewater and 72% of chromium was extracted directly from raw tannery effluents by using different quantities of water hyacinth. The Langmuir and Freundlich type isotherms were used to study the chromium biosorption process, and the results were found to be highly consistent with the Langmuir monolayer biosorption type isotherm. The results of kinetic investigation showed that the removal of chromium by water hyacinth roots followed a pseudo-second-order kinetic with a R² of 0.99618. The biosorption of chromium on water hyacinth roots was exothermic and spontaneous which were confirmed from the evaluation of thermodynamic parameters such as ΔG°, ΔH°, and ΔS°. The present research findings revealed that this naturally available plant could be utilized as very promising, environmentally friendly, and cost-effective biosorbent for removing chromium species from raw as well as diluted industrial wastewater systems.
... It was estimated that the economic separation efficiency could be achieved safely when the NaCl concentration is lower than 5000 mg/L at chromium concentration less than 1000 mg/L. Under these conditions, the permeate recovery and chromium removal can be of about 45% and more than 99%, respectively [59]. ...
The leather industry is characterized by the production of a huge amount of wastewater with a high organic/inorganic charge, causing widespread water and soil pollution. Pressure-driven membrane operations and membrane bioreactors have long been proven to be a valid approach for the treatment of tanning wastewaters aimed at the recovery of raw materials as well as for the removal of toxic and environmentally harmful substances. Such processes, opportunely integrated among themselves and/or with conventional physical-chemical and biological treatments, also provide useful protocols for the treatment of global wastewaters with significant advantages in terms of environmental protection, decrease of disposal costs, simplification of cleaning-up processes and saving of water and chemicals. This paper, as the state of the art, attempts to revise the potential and perspectives of membrane-based technologies in the leather industry with related applications in beamhouse, tanning and post-tanning operations as well as in the treatment of global wastewaters.
... In Egypt, the tanning business is one of the most significant sources of national income [4]. The total number of tannery projects in Egypt is about 300 and most of them are using the chromium tanning technique [5]. The tanning process using the chromium salts technique is effective, fast, and stable, with low cost during the operation and production processes [6,7]. ...
The tanning industry is considered one of the main sources of pollution. This study aims to investigate the efficiency of nano zero-valent iron (nZVI) and the nano zero-valent aluminum (nZVAl) particles for the removal of chromium (Cr) from aqueous solutions and tannery wastewater. For the aqueous solutions, the maximum removal efficiency of 5 mg/L Cr reached 81.2% using nZVAl and 77.6% using nZVI, under the following conditions: time 20 min, pH 3, stirring rate 200 rpm, and dosage 0.6 g/L. The adsorption data for chromium removal using nZVAl and nZVI fitted well to the Freundlich and Koble-Corrigan models, respectively. For both nanometals, the kinetic data fitted well to pseudo second order (PSO). Response surface methodology (RSM) and artificial neural network (ANN) models with r 2-value higher than 0.95 were found to be accurate in predicting chromium removal efficiency using both nanometals. The synthesized nZVI and nZVAl particles were applied to real tannery wastewater samples. The removal efficiencies of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), lead (Pb), nickel (Ni), and arsenic (As) using both nZVAl and nZVI exceeded 98%. For total phosphorus (TP), total nitrogen (TN), and hydrogen sulfide (H 2 S), nZVI demonstrated a higher removal efficiency compared to nZVAl. A significant increase was also reported for Cr removal, reaching 70% using nZVI and 74% using nZVAl.
... The major sources of Chromium are paint, electroplating, tannery, dye, and aluminum industries. Wastewater from the tanning operations is an significant source of the environmental pollution with chromium [8,9]. ...
Chromium is a dangerous heavy element with harm impact on environment, this study deals with removal of chromium from simulated aqueous solutions by date palm fibers (PDF) as biological products through fixed bed column and batch study. Iraq is one of the first countries in the number of palm trees and thousands of tons of palm fibers are thrown annually. In batch, several experiments were carried out with different operating conditions such as pH, contact time, initial concentration, dosage and shaking velocity. The best removal percentage was (84 %) at conditions of 150 min, pH of 3, 50 mg/l, 2 g/100 ml, and 200 rpm respectively at 25 ºC. The Freundlich and linear Langmuir were suitable with a correlation coefficient of 0.9738 for adopted variables. The fixed bed column study included many tests. The results of these tests showed that the removal percentage of chromium increases with decreasing in pH of aqueous solutions, initial concentration of chromium and flow rate. This study indicated that the increasing of contact time and height of adsorbent media leads to best removal percentage. The best removal percentage of chromium was (82%). This will lead to conclude that there is a small variance in the removal percentage between the two studies (batch and fixed bed column). Finally, it was noted that (PDF) is an impactive adsorbent material for chromium ions removal from the polluted water.
... Therefore, it is highly expected to explore an effective and economical treatment process to reduce Cr (VI) in wastewater. Nowadays, the technologies for reducing Cr (VI) to Cr (III) include photocatalysis (Sharma et al., 2019a(Sharma et al., , 2019bKumar et al., 2021), membrane separation (Hafez et al., 2002), biological process (Zakaria et al., 2007), precipitation (Almeida and Boaventura, 1998), and ion exchange (Kocaoba and Akcin, 2002). However, most of these approaches generally suffer from low efficiency, high cost and large chemical dosage. ...
[email protected] quantum dots ([email protected]), as novel flower-like hybrid materials, were firstly prepared through a simple reduction method. The [email protected] exhibited an outstanding catalytic performance for Cr (VI) reduction with a low activation energy (Ea = 18.9 kJ mol⁻¹) and a high kinetic constant (k = 0.4779 min⁻¹) in the presence of formic acid (HCOOH). Density functional theory calculations demonstrated that [email protected] exhibited an upshift of d-band center of active Ni atoms to promote the adsorption of both HCOOH and active H atoms, as well as an improved conductivity to boost the catalytic reaction kinetics, leading to the most favorable catalytic performance. This work may open up a new avenue towards the design and synthesis of novel MQDs-based hybrid catalysts for wastewater treatment.
... Two methods are employed in tanning of raw hides and skins namely: vegetable and chrome tanning. Most of the modern tanneries adopt the chrome tanning process because of speed, low cost and greater stability to the resultant leather [1,2]. The production processes can be divided into four categories: (i) Hides and skin storage and beam house operations (ii) Tan yard operations (iii) Post tanning operations and (iv) Finishing operations [3]. ...
... The major sources of Chromium are paint, electroplating, tannery, dye, and aluminum industries. Wastewater from the tanning operations is an significant source of the environmental pollution with chromium [8,9]. ...
... As per the toxicity level, chromium is one of the highest toxic metals. Various types of statistics show that chromium compound is found in the tannery waste water in an amount of 2500-8000ppm (Chandra et al., 1997), 2000-5000ppm (Hafez et al., 2002). But in this work 1100-1500ppm was found, because the samples were combined wastes. ...
... Depending on the chrome tanning process, chrome shaving dust in solid waste may contain 2.5 to 5 % of chromium (mostly trivalent chromium) [15,16]. Several researches suggested that wastewater contains 2500 ppm to 8000 ppm and 1300 ppm to 2500 ppm of chromium respectively [17,18]. The major chemical pollutants that come out from the tanning industry are sulfide and chromium; these chemicals spread into the local environment, which makes it harmful for the environment [19]. ...
This study was adopted to investigate the removal of Cr(III) and other physicochemical parameters of chrome
tan wastewater. For this purpose, three precipitating agents, CaCO3, NaHCO3, and MgO, were used to treat
chrome tan wastewater. After treatment, it was found, in three different dose trials, that each agent removed
almost 97-99.5 % of chromium. At the same time, it was observed that with the increase of doses, removal
percentage of TDS, conductivity, and turbidity of effluent were reduced. In the case of NaHCO3 and CaCO3,
Cr(III) removal percentage at optimum pH was found to be 99.97% and 99.95% respectively, whereas the
maximum removal percentage for MgO was found to be 99.98%. The NaHCO3 and CaCO3 were found to be
comparable to MgO for Cr(III) removal from chrome tan wastewater. The recovered chromium concentration
in the sludge for NaHCO3 and CaCO3 were also similar to that of MgO. This research suggests that these two
precipitating agents can be used in the same way as MgO, for Cr removal and recovery treatments. Moreover,
this recovered chromium can be reused, thus reducing the environmental pollution.
... •w aters (Alves et al, 1993). Therefore, in the case of Cr, further treatment is often mandatory such as: ion exchange resin, reverse osmosis and electrolysis have been investigated as methods of further purification iKocaoba and Akcin, 2002;Vlyssides and Israilides, 1997;Hafez et al, 2002). However, these methods are expensive and are often not considered cost effective for small sized industries. ...
... •w aters (Alves et al, 1993). Therefore, in the case of Cr, further treatment is often mandatory such as: ion exchange resin, reverse osmosis and electrolysis have been investigated as methods of further purification iKocaoba and Akcin, 2002;Vlyssides and Israilides, 1997;Hafez et al, 2002). However, these methods are expensive and are often not considered cost effective for small sized industries. ...
... Several studies have shown the efficiency of membrane technologies to remove Cr (in both trivalent and hexavalent state) using reverse osmosis (Çimen et al., 2014;Hafez et al., 2002), nanofiltration (Gaikwad and Balomajumder, 2017;Gomes et al., 2010;Muthukrishnan and Guha, 2008), ultrafiltration processes (Aroua et al., 2007;Korus and Loska, 2009) and others (Bey et al., 2011;Gherasim and Bourceanu, 2013). However, the studies available in the literature are still limited to synthetic/model solutions and only few works deals on naturally Cr-contaminated groundwater, as reported in section 4.3. ...
... Elimination of Cr(VI) from aquatic environments has been widely studied by various methods, such as adsorption (Pradhan, Das, & Thakur, 1999), chemical reduction followed by precipitation (Daneshvar, Salari, & Aber, 2002;Yin, Li, et al., 2017), bio-reduction and adsorption Zhong et al., 2017), and membrane separation (Hafez, El-Manharawy, & Khedr, 2002). Because Cr(III) is less soluble and can be easily adsorbed by soil colloids, reductive transformation of Cr(VI) to Cr(III) followed by precipitation using permeable reactive barriers (PRBs) filled with metallic iron has proved to be a promising technique to clean up Cr(VI) from groundwater (Melitas, Chuffe-Moscoso, & Farrell, 2001;Wilkin, Su, Ford, & Paul, 2005). ...
Continuous‐flow iron and bio‐iron columns were used to evaluate the effects of seepage velocity and concentration on Cr(VI) removal from groundwater. Solid‐phase analysis showed that microorganisms accelerated iron corrosion by excreting extracellular polymeric substances and generated highly reactive minerals containing Fe(II), which gave the bio‐iron column a longer life span and enhanced capacity for Cr(VI) removal via enhanced adsorption and reduction by reactive minerals. The bio‐iron column showed much higher Cr(VI) removal capacity than the iron column with increasing Cr(VI) loading, which was obtained by increasing the seepage velocity or influent Cr(VI) concentration from 95 to 1138 m yr⁻¹ and from 5 to 40 mg L⁻¹, respectively. When the Cr(VI) loading varied in a range of 0 to 10 mg L⁻¹ h⁻¹, the bio‐iron column had a 60% longer longevity and one‐ to sixfold higher Cr(VI) elimination capacity than the iron column. This result indicated that, under fluctuating hydraulic conditions [e.g., seepage velocity and Cr(VI) concentration], the presence of microorganisms can significantly boost Cr(VI) removal using Fe⁰–based permeable reactive barriers.
... Further, this can also be operated at high sludge concentrations [19]. MBRs are well appreciated for their efficiency in removing dissolved solids [20] [21]. Major concern of MBR system is fouling of membrane which indicates accumulation of rejected constituents on the membrane resulting in resistance to water transport through the membrane [22]. ...
Treatment of pharmaceutical wastewaters is a challenging task owing to their complexity and pollution load, variability in strength of waste streams accompanied with shock loads. Since no single treatment system is a viable option, integration of existing systems with advanced physical/chemical processes has been gaining attention for treatment of pharmaceutical wastewater. In the present study, two biological treatment methods were evaluated for their efficiency as pre-treatment system for RO which are sequencing batch reactor and membrane bioreactor. Efficiency of biological treatments tested SBR and MBR was pre-sented in terms of percentage removal of physico-chemical parameters. Total dissolved solids removal by SBR was 31.82% while MBR showed 29.25% reduction. Chemical oxygen demand removal by SBR was 69.54% while MBR showed 30.35% removal. Efficiency of combined treatments SBR-RO and MBR-RO was presented in terms of removal of total dissolved solids, COD and ammonia. TDS removal was the highest in the combination of SBR-RO with 95.94% removal, while MBR-RO combination resulted in 87.29% removal. Chemical oxygen demand was achieved maximum with the combination of MBR-RO 92.33% while competitive results were achieved with the combination SBR-RO also with 88.62% removal. Removal of ammonia was maximum with the combination SBR-RO 87.5%, while competitive results were obtained with MBR-RO 85.51%. From the results, it can be understood that SBR was efficient in removing ammonia, total dissolved solids and was equally competent in removing chemical oxygen demand. This study concludes that combined treatment of SBR-RO proves to be promising in treating pharmaceutical wastewaters.
... Nevertheless, this method of curing emits high load of salt to the environment contributing to about 70 % of TDS (Kanagaraj et al., 2004). Reports state that ~40,000 to 50,000 mg L -1 of salt is discharged from leather processing industry causing enormous pollution (Hafez et al., 2002). ...
The art of leather-making have been practiced for decades, and so are the effects of pollution generated. Freshly flayed animal hides/skins are preserved temporarily with common salt for storage and transport purposes. This method of preservation paves way for increased Total Dissolved Solids (TDS) in process water thereby causing enormous pollution. The present study investigates into the phyto based eco-friendly preservation of skins with paste obtained from the leaves of Citrus limon (Lemon). The phytochemical screening exhibited the presence of Terpenoids, Phenols, Steroids and Sterols, Phlobatannins, Saponins and Cardiac Glycosides. Analysis by GC-MS revealed the presence of 2-[2,6,6-Trimethylcyclohex-1-enyl] cyclopropane carboxylic acid, 1,2-benzenediol, 3[[(3,5-dichlorophenyl) imino]methyl], Pentadecanoic acid and Heptadecanoic acid in the methanolic extract of Lemon leaves. FT-IR analysis also confirmed their presence which helps in inhibiting the growth of bacteria thereby preventing the skins from degradation. The pollution load of soak liquor viz., TDS, Total Solids (TS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were also reduced substantially. The skins cured by this technique showed comparable physical strength of leather with respect to conventionally cured skins. Hence, application of plant based preservation method may help to considerably reduce the major problem of salinity associated with leather processing.
... [29][30][31][32] Cr can also exist in ground and surface waters discharged from industrial applications (e.g., leather tanning manufacturing). [33][34][35][36] Moreover, naturally occurring chromium [37][38][39] can exist in concentrations ranging from 0.02-50 μmol g −1 in soils. 40 Hence, CeO 2 NPs that bypass wastewater treatment to enter ground and surface waters can interact with these pre-existing redox-active species. ...
CeO2 nanoparticles (NPs) are extensively used in industrial applications due to their high redox-catalytic activities and, as a result, may appear in aquatic environments where other redox-active species may coexist. To better predict the fate and transport of these nanomaterials, a comprehensive, mechanistic understanding of the physicochemical behaviors and transformation of CeO2 NPs in complex, redox-active aqueous systems is needed. In this study, we investigated redox reactions of CeO2 NPs with Fe2+ and Cr(VI) (i.e., model redox-sensitive species) at pH 5. We found that the co-existence of 0.1 mM Fe2+ and 1 (or 5) μM Cr(VI)(aq) promoted formation of Fe(III) (hydr)oxides and increased CeO2 NP colloidal stability. Specifically, without Cr(VI), Ce3+(aq) was rapidly released from the CeO2/Fe2+ redox reaction, while the subsequent oxidation of Fe2+ to Fe3+ and formation of Fe(III) (hydr)oxides was slow. However, when Fe2+ and Cr(VI) coexist with CeO2 NPs, the dissolution of CeO2 NPs was slower than without Cr(VI), and Fe(III) (hydr)oxide precipitation on and near CeO2 NPs significantly increased. The fast formation of Fe(III) (hydr)oxides can be attributed to facilitated Fe3+ hydrolysis by Cr(VI)(aq). Consequently, these new hybrid Fe(III)-CeO2 NPs (i.e., CeO2 NPs coated with Fe(III) phases) formed during redox-induced surface transformations exhibited a higher hydrophilicity, a more positive surface charge, and a greater colloidal stability compared to CeO2 NPs in systems without Cr(VI). These findings reveal unexplored changes in surface chemistry and mobility of CeO2 nanomaterials in complex redox-active aqueous systems.
... Physicochemical methods for chromium removal include of electrochemical reactions, ion exchange, membrane technology, chemical treatments, or adsorption by activated carbon [9][10][11][12][13][14]. The use of activated carbon as an adsorbent can improve the quality of water. ...
The potential of palm kernel shell, as agricultural waste, to remove Cr (VI) from aqueous solution was evaluated. Effective parameters such as pH (2-8), temperature (20-80 °C), contact time (10-120 min), adsorbent concentration (0.1-1 g/L), and initial Cr (VI) concentration (10-100 mg/L) were all studied to attain the maximum removal efficiency. Results show the adsorption capacity increases as pH value decreases and the optimum pH value is pH= 2.0. The other optimal conditions are temperature 40 °C, contact time 45 min, adsorbent concentration 0.5 g/L and initial Cr (VI) concentration 10 mg/L. The equilibrium data for chromate adsorption well fitted to Freundlich equation, with maximum adsorption capacity of 125 mg/g. This novel activated carbon derived from palm shell powder has been found to be effective for the removal of Cr (VI) and not noxious to the ecosystem.
... During chrome tanning and re-tanning operation, 60-70% of chromium has been used to bind with hide and skin and other 30-40% of excess unused chromium is discharged into the final effluent, Chowdhury et al (2013), Abdulla, Hafez et al (2002). According to literature survey, it has been found that the concentration of Cr ion in untreated tanning wastewater varies from 1300 to 8000 ppm depending on the adopted operational procedure, Hafez et al (2002), Chaudry (1998). Where it has been proven that the tolerable limit of chromium ion from the discharge of effluents into water bodies should be within the range of 0.05-10 ppm, Bosnic (2000). ...
Presence of chromium, which is toxic, non-biodegradable and having a long natural life, in the industrial wastewater discharge can cause serious health hazard in an ecologically sustainable environment. The leather tanning industry in Bangladesh discharges such wastewater without treatment. There are some current traditional processes used to control chromium level in effluent discharged into the natural environment, but those processes also produce harmful by-products and consume energy thus need improvement for the sustainable world of the future. This paper presents the development of an innovative chromium reduction process using one of the residential wastes, such as eggshell, as the raw material. This process has been proved to produce the chromium reduction efficiency very close to currently used commercial CaCO 3 process. The experiment was done on tannery effluent by precipitation method to remove chromium. For comparative analysis, in addition to eggshell, snail shell and commercial CaCO 3 were also used as precipitant. Chromium concentration was measured using Atomic Absorption Spectrophotometer (AAS) and found to be decreased at least 99% for egg and snail shells which were better than commercial CaCO 3. Moreover, the precipitate occurred here was further treated with concentrated H 2 SO 4 to form a by-product solution of basic chromium sulfate, which could again be as tanning liquor resulting a
... But these techniques have a significant problem in terms of disposal of the precipitated wastes (Ozdemir, Karatas, Dursun, Argun & Dogan, 2005;Meunier, Drogui, Montane, Hausler, Mercier & Blais, 2006). The sedimentation (Song, Williams & Edyvean, 2000), electrochemical processes (Oda & Nakagawa, 2003), biological operations (Kapoora, Viraraghavana & Cullimoreb, 1999), cementation (Filibeli, Buyukkamaci & Senol, 2000), coagulation/flocculation (Song, Williams & Edyvean, 2004), filtration and membrane processes (Hafez, El-Manharawy & Khedr, 2002), chemical precipitation and solvent extraction (Macchi, Pagano, Pettine, Santrori & Tiravanti, 1991) are also used. Some of the low cost, non-conventional adsorbents include anaerobic sludge (Ulmanu, Marañón, Fernández, Castrillón, Anger & Dumitriu, 2003), apple residue (Lee, Jung, Chung, Lee & Yang, 1998), sawdust (Shukla, 2005), rice Polish (Singh, Rastogi & Hasan, 2005), clay (Farrah, & Pickering, 1977), zeolite (El-Kamash, Zaki & El Geleel, 2005), fly ash (Al-Qodah, 2006), chitosan (Jha, Iyengar & Rao, 1988), waste tea (Orhan & Büyükgüngör, 1993;Ahluwalia & Goyal, 2005), seaweeds (Da Costa & De França, 1996), polyaniline coated on sawdust (Mansour, Ossman & Farag, 2011), and Carica papaya plant (Sheikh, Apon & Hashem, 2017) which have been used for the purpose, but all these attempts have become inefficient because of the less available nature of adsorbent. ...
... There exists many methods in literature which can remove metal ion pollutants from aqueous solutions, and such approaches can be in the form of physical, chemical, and/or biological techniques (Sahinkaya et al., 2012). The traditional physicochemical methods used for (Cr) removal including, but are not limited to chemical precipitation (Monser and Adhoum, 2002), oxidation or reduction (Sedlak and Chan, 1997), ion exchange (Yang et al., 2014), electrochemical treatment (Giri et al., 2012), membrane technology (Hafez et al., 2002), evaporation recovery (Tiravanti et al., 1997), and adsorption onto activated carbon (Deveci and Kar, 2013;Suksabye and Thiravetyan, 2012). Adsorption plays an important role in the improvement of water quality; generally, activated carbon can be used to adsorb metals. ...
In aqueous solutions, hexavalent chromium Cr(VI) was successfully removed by activated carbon “Z. jujuba rubidium carbonate-activated carbon” obtained from waste lignocellulosic material (Ziziphus jujuba cores). Rubidium carbonate was used to prepare Z. jujuba rubidium carbonate-activated carbon by chemical activation using a 1:1 w/w ratio. Our results indicate that the obtained surface area of the activated carbon was equal to 608.31 m²/g. The adsorption study of Cr(VI) was investigated under batch conditions at constant stirring speed (220 r/min). Factors such as pH (1–6), temperature (20–40°C), adsorbent concentration (0.5–3 g/l), and initial Cr(VI) concentration (50–500 mg/l) were all studied to attain the maximum removal efficiency. Prior to the adsorption process, the morphology, elementary composition, and loss mass of activated carbon were characterized using scanning electron microscopy, X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Fourier transform infrared analysis of the adsorbent demonstrated the presence of key functional groups associated with the adsorption phenomenon such as those of hydroxyl and aromatic groups. The obtained results showed that the optimal conditions for a maximum adsorption efficiency are 2 for pH, 1 g/l for activated carbon dosage and 100 mg/l for Cr(VI) concentration. The removal percentage increased from 27.2 to 62.08%. The kinetic sorption was described by a pseudo-second-order kinetic equation (R² ≈ 0.995). The Tóth (R² = 0.997) and Elovich models were best to explain the sorption phenomenon. Thermodynamic studies showed that the adsorption of Cr(VI) onto activated carbon was feasible, spontaneous, and endothermic at 20–40°C. This novel Z. jujuba rubidium carbonate-activated carbon derived from Z. jujuba core has been found to be effective for the removal of Cr(VI) and not harmful to the ecosystem.
... The high TDS stream from the tannery and the outlet concentration stream from the ambient air evaporator is sent to open ponds of evaporation 14 . The concentration of the solutions increases with depth. ...
The waste generated from tanning process poses a threat to the environment and has a major challenge of waste management. In India, all tannery industries are bound to achieve Zero Liquid Discharge (ZLD) with the objectives of recovery of water and prevention of environment. This study deals with the mechanical evaporation to increase the efficiency of concentrating the tannery effluent. The evaporator works on the principle of using ambient air instead of hot air for the process of evaporation. The project was undertaken to understand the process flow and design of the evaporator setup and to optimize the process parameters to increase the outlet concentration of the effluent to 85000mg/L for the single run, so that the area required for sludge drying was reduced.The outlet concentration was varying from 42000mg/l to 43306mg/l with a mass of dry air as 38570kg/h. The preheating of air improves the concentration of outlet to 55690 mg/l.
... In addition, the cost of the chromium metal is also high and it is possible to recover chromium from the wastewater (Fabiani et al., 1996;Ludvic, 2000). Kocaoba and Akin (2002) and Hafez et al. (2002) have reported that the chromium concentration in the tanning wastewater varies from 1300 to 2500 mg/L and 2500 to 8000 mg/L, respectively. ...
Most tanneries in Ethiopia (90%) do not treat and very few (10%) partially treat
their effluent before discharging it into the receiving water bodies. The untreated
tannery effluent causes tremendous pollution of water resources in the country,
especially due to its high organic loading and chromium content. Chromium(III)
salts are the most widely used chemicals for tanning processes, but only about
60-70% of total chromium salts reacts with the hides and about 30-40% of the
chromium remain in the solids and liquid wastes (especially spent tanning
solutions). Therefore, the removal and recovery of the chromium content of these
wastewaters is necessary for environmental protection and economic reasons.
The purpose of this study was to develop an alternative process for removing and
recovering trivalent chromium from tannery wastewater via chemical
precipitation with sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2) and
magnesium oxide (MgO). The effects of pH, stirring time, settling rate and sludge
volume were studied in batch experiments. Flame atomic absorption
spectrometry was used to determine Cr concentration. The results showed that
removal efficiencies of the precipitating agents NaOH (99.97%), Ca(OH)2
(99.97%) and MgO ( 99.98%) at optimum pH values were not significantly
different. However, there was a significant difference in sludge volume of NaOH
(590 mL), Ca(OH)2 (412 mL) and MgO (85 mL). The optimum pH of 9.8-10.3 with
removal efficiency of 99.98% and the good sludge with high settling rate and
lower volume was obtained using MgO precipitating agent. Hence the MgO was
found to be a good precipitating agent for removal and recovery of chromium
from tanning wastewater. The basic chromium sulfate (BCS) recovered at pH 2.8
is suitable for tanning mixed with fresh BCS from the market.
... The use of physical-chemical methods for lead removal including electrodialysis processes, chemical precipitation [4], reverse osmosis [5] and ion exchange [6], due to the high cost, lack of complete elimination of lead as well as waste disposal, has their own limitations. Due to the fact that most of these methods, when the concentrations of heavy metals in the environment are 10-100 ppm, may be ineffective and uneconomical, however, concentrations of less than 1 ppm are permitted to discharge into surface water [7]. ...
Nasturtium officinale powder (NoP), with leached active ingredients, was used here to adsorb lead (Pb), as a water pollutant. The effects of several variables on the removal of lead including initial pH, contact time, adsorbent dosage and initial concentration of lead were studied. The response surface plots were used for estimating the interactive effects of variables. The statistical analysis and modeling by response surface methodology and central composite design are demonstrated to be effective and reliable in finding the optimal conditions for the adsorption of lead onto NoP. The results showed that the biosorption conditions have significant effects on the removal of lead, and 10 g L–1 of NoP had the best adsorption efficiency. The equilibrium data was analyzed using Langmuir and Freundlich isotherms models. The pseudo-second-order kinetics model best explained the Pb biosorption by NoP of any dosage.
... The removal of chromium from wastewater may be accomplished by precipitation using the addition of lime and caustic soda [11]. In order to reduce chromium from tannery effluents, many researchers used different chemicals and materials like bacillus subtilis [12], magnesium oxide, three precipitation agents calcium hydroxide, sodium hydroxide and magnesium hydroxide [13], aspergillus oryzae [7], alge, fungi and bacteria [14], reverse osmosis membrane [15] employed and amberliet IR 120 resin [16]. All of the methods described above are involved additional chemicals or reagents that increase the costing of tannery effluent treatment. ...
Effective wastewater management is paramount to safeguarding water resources and soil quality in pursuing sustainable leather production. With increasing awareness of industrial environmental impacts, there is a growing imperative for green wastewater treatment practices within the leather industry. This involves employing biodegradation, oxidation, and aeration techniques to purify wastewater streams. By harnessing the power of microbial activity, organic compounds and pollutants present in wastewater are efficiently decomposed, thereby mitigating the environmental footprint associated with leather production. Furthermore, adopting advanced membrane technologies such as ultrafiltration, nanofiltration, and reverse osmosis is a promising avenue for eco-friendly wastewater treatment in leather manufacturing processes. These techniques mimic natural filtration processes, effectively removing contaminants from wastewater and yielding purified water that meets stringent quality standards. By embracing such sustainable wastewater treatment solutions, the leather industry reduces energy consumption and contributes significantly to mitigating water pollution, enhancing its overall sustainability profile.
The main cause of agricultural soil pollution that endangers human health is tannery waste. Experiments were carried out to assess the effects of green material (GM), rice straw (RS), and rice straw biochar (RSB) on Triticum aestivum L. grown in tannery effluent-contaminated soil in the district Kasur, Pakistan. The application of GM, RS, and RSB significantly (P ≤ 0.05) reduced the concentration of heavy metals (HMs) such as Cd, Pb, and Cr in amended soil. The bioaccumulation of Cd decreased by up to 59–34%, Pb by up to 58–42%, and Cr by up to 30–34% in Triticum aestivum L. shoot and roots with RSB amendment. Increased concentration of chlorophyll a by up to 74%, 30%, and 110%, chlorophyll b by up to 138%, 70%, and 225%, and carotenoids by up to 87%, 37%, and 140% was measured with GM, RS, and RSB amendment. However, reduced concentrations of SOD by up to 41%, 36%, and 72%, POD by up to 7%, 20%, and 55%, and CAT by up to 29%, 22%, and 38% were recorded with GM, RS, and RSB amendment. Data revealed that RSB was beneficial to Triticum aestivum L. growth, soil HMs remediation, and activating antioxidant enzymes. RSB can be used as a suitable amendment in the remediation of tannery polluted soil.
As a highly complex aqueous effluent, tannery wastewater from leather industry should be treated appropriately before discharging into the environment. Membrane technology has been shown to be a promising approach for tannery wastewater treatment as it may achieve “Zero Liquid Discharge (ZLD)”. This work, as the state-of-the-art, attempts to review the world-wide research trends of membrane technologies, the technical recapitulation and recent advances of such technology for tannery wastewater treatment. Generally, manufacture membrane, membrane-based integrated process, MBR, NF, UF and RO are the hotspots in this field. Details of different membrane technologies configured for tannery wastewater treatment, such as membrane materials, scale, membrane modules, operating conditions and removal efficiency of pollutants, are also summarized. It should be noted that membrane fouling is still a major challenge in the membrane technology during tannery wastewater treatment. Therefore, process coupling, either within diverse membrane technologies or between membrane and non-membrane technologies, is considered as a promising alternative to treat the leather tannery wastewater in the future.
Graphical abstract
In this study, the activated carbon with Fe3O4 nanoparticles was synthesized and employed as an effective tool to remove the Cr (VI) from the aqueous solution. The process inputs like concentration of Cr (VI), the dosage of Fe3O4 nanoparticles in activated carbon, and pH of the aqueous solution were optimized by response surface methodology, and their effects were studied. The statistical analysis by ANOVA showed that the process inputs were significantly affected the removal rate, with the maximum impact provided by the pH of the aqueous solution. The best parameters were identified to be pH of 3, aqueous solution concentration of 12 mg/L, the dosage of 1.5 g/L, and adsorption time of 40 min. SEM, EDS, and FTIR characterized the synthesized activated carbon/Fe3O4 samples with magnetic characteristics. Adsorption isotherms and adsorption kinetics analyzed the chemical stability of the synthesized nanocomposite.
In the leather tanning process or tannery, Cr solution is usually used to modify leather properties. This results in Cr containing wastewater, which becomes a crucial issue. One promising method for removing Cr from tannery wastewater is by using subsurface flow constructed wetland (SSF-CW). A combination of adsorption and phytoremediation that occurs in the SSF-CW removes Cr from wastewater. In this research, the effect of vegetation and media on Cr removal was investigated. Echinodorus palaefolius was used as a phytoremediation agent, while wood charcoal and natural zeolite were used as media. The experiment was conducted in 4-different SSF-CW reactor configurations, namely CTT (wood charcoal-zeolite; no plant), CDT (wood charcoal-zeolite; with plant), ZDT (zeolite; with plant) and ADT (wood charcoal; with plant). Each reactor was filled with 70 L Cr contained water that was recirculated within the reactor for 15 days. Evidence revealed that Echinodorus palaefolius significantly increases the removal of Cr from wastewater, compared to that of without those plants (wood charcoal-zeolite medium only). Using an initial concentration of Cr of 2.05 mg/L, removal percentage is 63.7, 86.83, 70.37, and 83.05% for CTT, ZDT, ADT, and CDT, respectively. It is also found that zeolite media performed much better than charcoal. A combination of zeolite medium and Echinodorus palaefolius (ZDT) produced the highest Cr removal. In addition to that, despite its Cr intoxication indication, the Echinodorus palaefolius was able to grow/regenerate during the experiment.
Nowadays, Egypt built the biggest industrial area for tanning industries; this industry produces a vast amount of chromium in the tannery wastewater effluent. This study successfully prepared and characterized GT-nZVI by reducing agents extracted from soft black tea. The prepared GT-nZVI was characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis of x-rays (EDAX) analysis. The chromium removal efficiency reached 97.1% and 73.7% from an initial chromium concentration of 1.0 and 9.0 mg/L, respectively. The optimum removal efficiencies were achieved using 0.6 g/L GT-nZVI at acidic pH 5 after 30 min of shaking at a rate of 250 rpm. The equilibrium isotherm and kinetic results indicated that the adsorption of chromium onto GT-nZVI agrees with the Koble-Corrigan model with the lowest summation of errors of 0.394 and a Pseudo-Second-Order adsorption with the lowest summation of errors of 0.07. An artificial neural network (ANNs) was built to describe the factors affecting the adsorption process by 6 inputs, 4 hidden layers, and 1 output. The results obtained indicated that the initial concentration and GT-nZVI dose are the most significant variables that influence the adsorption process. The response surface methodology (RSM) equation was developed to allow the prediction of chromium removal efficiency at different operating parameters. Finally, this study strongly supports using GT-nZVI for chromium removal from tannery effluents.
Chemical modification of plasticized polyvinylchloride with polyethylenepolyamine leads to anion exchange resin (PPE‐1). Different characterization techniques, such as XRD, FTIR, and SEM of PPE‐1 anion exchanger revealed weak base amino groups as well as macroporous structure morphology. PPE‐1 turned out effective to remove hexavalent chromium ions from aqueous media. Corresponding adsorption kinetics best fit the pseudo‐second order model that followed a Freundlich isotherm. In the case of hexavalent chromium ions, the maximum adsorption capacity of PPE‐1 was 218.4 mg/g. Thermodynamic data revealed spontaneous endothermic processes and a chemisorption reaction. In addition, results show that the anion exchanger (PPE‐1) has 98% for removing hexavalent chromium ions containing from wastewater.
Aluminium oxide modified onion skin waste (Al 2 O 3 /OSW) was characterized and used for adsorption of metal ions (Pb ²⁺ and Cd ²⁺ ) in this study, and the relations between sorbent properties and metal ion sorption were investigated. The effects of adsorption process conditions on metal ion removal efficiency, including initial cation concentration, contact time, adsorbent dosage and pH, were examined. The obtained adsorption data were analyzed by various adsorption isotherm and kinetic models. It was found that the optimum values of the initial concentration, contact time, adsorbent dosage and pH were 10 mg/L, 120 min, 1.6 g/L and 6.0, respectively. At these optimum conditions, maximum removal percentages of Pb ²⁺ and Cd ²⁺ were 91.23 and 94.10%, respectively. The isotherm and kinetic studies showed a multilayer adsorbate-adsorbent system with the dominance of the chemisorption mechanism. The study concluded that onion skin waste is a viable, cheap and effective alternative for removing heavy metal ions from water/wastewater.
This review is aimed at exploring the possibilities of recovering Chromium ions using several low-cost adsorbents through wastewater processing. In the past, several traditional methods were employed for removing Chromium ions. These included precipitation, evaporation, electroplating and ion exchange. However, these processes were associated with various limitations, which included the treatments to be restricted to a certain concentration of the Chromium ions. Therefore, the process of using low-cost adsorbents can be deemed as an eco-friendly one. At the moment, an enormous amount of natural materials and agricultural waste are produced, which extremely harmful to the environment. Thus, adsorption is an alternate process for removing Chromium ions. Based on the enhanced characteristics of the process of adsorption, such as cost-effectiveness, improved adsorptive properties, and increased availability, the process is definitely an economical one for removing Chromium ions. This review provides a brief appraisal of the relevant literature which exists on the low-cost adsorption for removing Chromium from polluted wastewaters. Additionally, in order to comprehend the overall adsorption process of low-cost adsorbents, this review will also explore the various existing adsorption models. These include the isotherm, kinetics, and thermodynamics along with the impact of various factors on the process of adsorption.
Watermelon peel residues were used to produce a new biochar by dehydration method. The new biochar has undergone two methods of chemical modification and the effect of this chemical modification on its ability to adsorb Cr(VI) ions from aqueous solution has been investigated. Three biochars, Melon-B, Melon-BO-NH2 and Melon-BO-TETA, were made from watermelon peel via dehydration with 50% sulfuric acid to give Melon-B followed by oxidation with ozone and amination using ammonium hydroxide to give Melon-BO-NH2 or Triethylenetetramine (TETA) to give Melon-BO-TETA. The prepared biochars were characterized by BET, BJH, SEM, FT-IR, TGA, DSC and EDAX analyses. The highest removal percentage of Cr(VI) ions was 69% for Melon-B, 98% for Melon-BO-NH2 and 99% for Melon-BO-TETA biochars of 100 mg·L−1 Cr(VI) ions initial concentration and 1.0 g·L−1 adsorbents dose. The unmodified biochar (Melon-B) and modified biochars (Melon-BO-NH2 and Melon-BO-TETA) had maximum adsorption capacities (Qm) of 72.46, 123.46, and 333.33 mg·g−1, respectively. The amination of biochar reduced the pore size of modified biochar, whereas the surface area was enhanced. The obtained data of isotherm models were tested using different error function equations. The Freundlich, Tempkin and Langmuir isotherm models were best fitted to the experimental data of Melon-B, Melon-BO-NH2 and Melon-BO-TETA, respectively. The adsorption rate was primarily controlled by pseudo-second–order rate model. Conclusively, the functional groups interactions are important for adsorption mechanisms and expected to control the adsorption process. The adsorption for the Melon-B, Melon-BO-NH2 and Melon-BO-TETA could be explained for acid-base interaction and hydrogen bonding interaction.
Industrial activities that consume water generate wastewater as a by-product of processing which introduces various contaminants such as heavy metals into the neighbouring water bodies that creates adverse effects on the surrounding environment. Tannery industry releases more toxic effluent than most industries, which directly and indirectly exerts stress on various ecosystems. The heavy metal chromium (Cr), one of the pollutants found in tannery effluent, is very much detrimental to human health, animals, and plants. Conventional physico-chemical and biological processes can remove this heavy metal in considerable amounts. Recently, various applications of advanced technologies such as membrane technology, electrocoagulation, ion exchange, and electrodialysis for tannery wastewater have been growing due to their relative advantages over other technologies in terms of sustainability. This paper represents the review of various available techniques as well as represents a case study of chromium removal from tannery effluent by a low-cost absorbent.
PolyHIPEs membrane prepared with styrene (St), divinylbenzene (DVB), and ethylhexyl acrylate (EHA) can yield a unique pore structure provided by large voids highly interconnected by many small window throats. With the advantageous pore structure, PolyHIPE presents a potential as a support for carrier facilitated transport membrane. Tricaprylmethylammonium chloride (Aliquat 336) can be efficiently incorporated into the PolyHIPE membrane by a two-step solvent-nonsolvent method to obtain an Aliquat 336-immobilized PolyHIPE membrane with good stability. The study of Cr (VI) transport through Aliquat 336-immobilized PolyHIPE membrane indicates that the membrane has high initial flux and maxima stripping flux (Jf⁰=15.01 (μmol/m²s), Jsmax=6.15 (μmol/m²s)). The reusability study shows that the Aliquat 336-immobilized PolyHIPE membrane can maintain high Cr(VI) recovery efficiency even after 15 cycles of operations. The developed membrane was also used in the separation of Cr (VI) from other anions (i.e., SO2-⁴ and NO3⁻) and other cations (i.e., Ni (II), Mg (II) and Cu (II)) with good selectivity.
The new method for treatment of waste waters from tanneries containing chrome and large amounts of other inorganic compounds has been studied. It was found that the addition of cement at suitable temperature and pH results in a decrease of Cr(III) and Fe(III) contents. The method has been verified in practice in five tanneries. It is very simple, cheap and effective in all cases with very different composition of tannery chrome-containing wastes.
Removal of Chromium from Ion Exchange Reagent Solution
- Siegel
S. Siegel and D. Clifford, Removal of Chromium
from Ion Exchange Reagent Solution, EPA Report
No. 600/2-83-007, 1988.
Studies on pollution abatement of wastes from leather industries Assomac Servizi SRL and EGLTALEC Report: Preparation of a Master Plan and Conceptual Pro-tection for the New Leather Tanning Area
- A R Khwaja
A.R. Khwaja, Studies on pollution abatement of wastes from leather industries. Ph.D. thesis, Univer-sity of Roorkee, India, 1998. Assomac Servizi SRL and EGLTALEC Report: Preparation of a Master Plan and Conceptual Pro-tection for the New Leather Tanning Area, Badre City, Cairo, Egypt, 1998. Z. Kowalski, Treatment of chromic tannery wastes, J. Hazard. Mater., 37 (1994) 137-144.
Preparation of a Master Plan and Conceptual Protection for the New Leather Tanning Area
- Assomac Servizi
- Egltalec Report
Assomac Servizi SRL and EGLTALEC Report:
Preparation of a Master Plan and Conceptual Protection for the New Leather Tanning Area, Badre
City, Cairo, Egypt, 1998.
Development of a management system to treat wastewater effluent and use clean technology for chromium recovery from El-Radio and Cairo—Tan tanneries
- Hafez
A.I. Hafez, Development of a management system
to treat wastewater effluent and use clean technology for chromium recovery from El-Radio and
Cairo-Tan tanneries, US and Egypt Cooperation
Project Report No. Env2-004-044, 2000.
Studies on pollution abatement of wastes from leather industries
- A R Khwaja
A.R. Khwaja, Studies on pollution abatement of
wastes from leather industries. Ph.D. thesis, University of Roorkee, India, 1998.