Production of materials with alumina and ashes from incineration of chromium tanned leather shavings: environmental and technical aspects

The leather tannery industry produces a significant amount of solid and hazardous wastes. Chromium-containing wastes like tanned shavings used to be incinerated in order to recover energy. The incineration process generates ashes that must be disposed of. This paper is a report on the results of the evaluation of technological properties and environmental compatibility of products made of alumina and ashes from incinerated chrome tanned shavings. The raw materials, tannery ashes and alumina were mixed together in different proportions. The ceramic bodies were molded using a hydraulic press and fired with a heating rate of 100 K/h until 1400 degrees C for 4 h in a muffle furnace. The ceramic specimens were characterized regarding physical, mechanical and thermal properties. Leaching tests, according to Brazilian, German and Dutch regulations, were performed on ceramic bodies containing different additions of ash. Results show that the ceramic materials produced are acceptable for refractory applications.     

Waste with chrome in the Portland cement clinker production

Hazardous wastes, coming from industries are usually used in the Portland cement production in order to save energy, costs and/or stabilize toxic substances and heavy metals inside the clinker. This work focuses on the effect produced on the Portland cement clinker when it is obtained using tanned leather shavings whit chrome salts as part of the process. The raw materials were clinkered in laboratory with different percentages of shavings, which contained 2% of Cr(2)O(3). DTA-TG of the raw mixtures was performed to evaluate the thermal behavior changes that can take place during the clinkering process, analyzing the crystalline phases obtained by XRD. The milling behavior of clinkers was studied, analyzing also the refractoriness variation on those clinkers. The chrome retention was evaluated by leaching tests. The structural modification determined by the chrome presence in the silicate structure brought consequences in the hydration speed, mechanical resistance and pore distribution.     

Pickle-free chrome tanning using a polymeric synthetic tanning agent for cleaner leather processing

Stringent environmental regulations on the discharge of pollutants from various industries have prompted researchers to seek the development of eco-benign technologies. Conventional chrome tanning in leather processing discharges significant amounts of chromium, total dissolved solids and chlorides. Hence, tanners are looking for new product-process innovations towards low-waste and high exhaust chrome tanning. A polymeric syntan, which can enable pickle-free chrome tanning using commercial basic chromium sulphate, has been developed. A convenient process for tanning goatskins as well as cow hides has been designed. This method enhances the uptake of chromium to above 90%. Although the developed process is a highly reactive system, the tanned leathers are free from physical deposition of chromium as seen from microscopic analysis. The distribution of chromium in thicker cow sides is uniform and comparable to that of conventional tanned leathers even at reduced dosage. Further, the novel product-process helps to reduce the chemical oxygen demand (COD), total dissolved solids (TDS) and chlorides in the spent tan liquor by 50, 80 and 98% respectively. The product offers full, soft leathers having a shrinkage temperature comparable to that of conventional chrome tanned leathers. This integrated process provides reduction in chemicals, water, time and power consumption. Thus the novel product/process developed not only seeks advantages in reducing pollution loads but also seems to be techno-economically viable.     

Simultaneous sorption of phosphate and phenanthrene to inorgano-organo-bentonite from water

The nonbiodegradable organic pollutants and excess phosphate can not be effectively removed from municipal wastewater by the widely used bioprocess, thus they are harmful to aquatic environment. In this investigation, the feasibility of utilizing inorgano-organo-bentonite (IOB), which was bentonite mineral modified with both Fe polycations and cetyltrimethylammonium bromide (CTMAB), was explored to simultaneously remove phosphate and phenanthrene from water. The results showed that the IOB had strong affinity for both phosphate and polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene in water. It was found that more than 95% phosphate and 99% phenanthrene were removed from water within 30 min. The sorption of phosphate on IOB proved to be an anion/OH(-) exchange reaction. Compared with organobentonite and bentonite mineral, the settlement separation of IOB from aquatic phase was greatly improved. The residual turbidity reached a minimum value of 10 nephelometric turbidity units (NTU) in 60 min. It was indicated that IOB is a favorable sorbent and can simultaneously remove nonbiodegradable organic pollutants such as phenanthrene and phosphate after the bioprocess in wastewater treatment.     

Buffing dust as a filler of carboxylated butadiene-acrylonitrile rubber and butadiene-acrylonitrile rubber

Buffing dust from chrome tanned leather is one of the difficult tannery wastes to manage. It is also hazardous to both human health and the environment. The scientific literature rarely reports studies on dust management, especially on its utilization as a filler for elastomers. In this connection we have made an attempt to use this leather waste as a filler for rubbers such as XNBR and NBR. The addition of the buffing dust to rubber mixes brought improvement in mechanical properties, and increase in resistance to thermal ageing as well as in electric conductivity and crosslink density of vulcalizates.     

天然生物质材料吸油性能研究

采用小麦秸秆、玉米秸秆、锯末、中药渣作为吸油材料,重点研究了吸附材料粒径、吸附时间以及不同油品对这4种天然生物质材料的吸油性能的影响。同时,研究对比了这4种材料的吸水性能和保油能力。在对原油进行吸附实验时,发现锯末和小麦秸秆在0.25～0.83mm粒径范围内具有较好的吸油性能,吸油量分别为5.79和6.02g/g,其次为玉米秸秆,0.15～0.18mm之间的材料吸油量最大能达到5.02g/g,而中药渣在0.18～0.20mm之间的吸油量仅为2.37g/g。比较4种材料对有机物甲苯及植物油的吸附性能发现,其对原油的吸附效果优于植物油和甲苯。材料均有一定的保油能力,而锯末的保油能力最高,其油水比>11。由于天然生物质材料属固体废物,其吸油后可直接作为燃料使用,可达到以废治废的目的,因此在含油污水处理领域具有较好的开发和应用前景。     

Governing factors for motor oil removal from water with different sorption materials

This paper has been focused on the sorbent efficiency for motor oil removal from water. Two types of sorbents were investigated: organic and inorganic. Natural wool fibers (NWFs) and recycled-wool-based nonwoven material (RWNM)) were tested as organic type of sorbents. Sepiolite, bentonite and zeolite have been chosen as representative inorganic sorbents. Sorption was carried out in batch sorption system. Efficiency of oil removal was determined by measuring the oil concentration before and after the sorption process. Extractive-gravimetric method and refractive index determination have been applied as analytical methods for determination of oil concentration in water. Governing factors for sorbent efficiency were proposed, analysed and compared. It was concluded that sorption process is mostly affected by mass of sorbent, sorption time, temperature and pH value of water. NWFs, which were the most efficient sorbent showed maximal efficiency and maximal sorption capacity: 0.1 g of NWFs after 10 min at 20 degrees C and pH 8.00 sorbed 3.3 g of motor oil from 300 mL of water polluted with 4.5 g of motor oil. Maximal efficiency for all sorbents investigated was reached after 30 min of sorption processes, it was 95.0% for NWF, 43.0% for NRWM, 20.7% for sepiolite, 19.6% for bentonite and 21.2% for zeolite. Physical adsorption onto all sorbents is a favorable process (sorption efficiency decrease with increasing temperature) while sorption onto bentonite and zeolite is a result of both physical adsorption and chemisorption (sorption efficiency increase with increasing temperature, up to 80 degrees C).     

Butane extraction of model organic pollutants from water

In this study, n-butane (n-C(4)H(10)), a by-product of the oil refining process, was used as the extractant to remove various model organic pollutants including halogenated hydrocarbons, phenols and aromatic compounds from aqueous matrices. The presence of salt, inorganic acid and dissolved organic materials in the aqueous matrix were found to have little influence on the removal efficiency. High removal efficiencies are readily achievable for a great number of organic pollutants. The removal efficiencies for hydrophobic pollutants were greater than 90% for a single stripping stage for pollutants with a distribution constants (K(D)) greater than 45 and for a n-butane to aqueous phase ratio of 1-5. Results were also reported for the removal of residual butane in treated effluent by combinations of depressurization, air stripping and elevating operating temperature.     

Functionalized multi-walled carbon nanotubes for oil spill cleanup from water

The growing global economy resulted in an incessant increase in transportation and exploitation of oil. Hence, the oil spillage has been considered a serious threat to aquatic and terrestrial ecosystems. Therefore, water purification has been considered a major challenge around the world. There are numerous classical methods available for oil removal from water, but owing to multiple defects and disadvantages, research efforts have focused to find such adsorbents which can improve oil adsorption capability. Traditional adsorbent material typically applied in oil removal includes activated carbon, organoclays, wool, zeolites, etc. These materials suffer from several drawbacks such as low absorption capacity, non-selective absorption, and complicated reusability, whereas nano-adsorbents offer multiple advantages such as having multiple sorption sites, large surface area, short intra-particle diffusion distance, tuneable pore size, and ease of low-temperature modification. Multi-walled carbon nanotubes (MWCNTs) are extensively used adsorbent materials with a strong affinity for the removal of organic pollutants. The functionalization MWCNTs further increase the sorption capacity of adsorbents manifolds to remove organic materials. These nanocomposites are also compatible with green materials and considered environmentally friendly adsorbents. This review paper aims at providing an insight to understand the properties of the MWCNTs and their potential use to adsorb hydrocarbons from water. Moreover, the synthesis methods of those materials, their modification procedures including the functionalization with metal oxide nanoparticles, and applications are also discussed in detail.

Graphic abstract

     

Removal of arsenic from water using Fe-exchanged natural zeolite

An elevated arsenic (As) content in groundwater imposes a great threat to people worldwide. Thus, developing new and cost-effective methods to remove As from groundwater and drinking water becomes a priority. Using iron/aluminum hydroxide to remove As from water is a proven technology. However, separation of As-bearing fine particles from treated water presented a challenge. An alternative method was to use coarse-grained sorbents to increase the flow rate and throughput. In this research, a natural zeolite (clinoptilolite) was exchanged with iron(III) to enhance its As removal. Batch test results showed a Fe(III) sorption capacity of 144 mmol/kg on the zeolite. The As sorption on the Fe-exchanged zeolite (Fe-eZ) could reach up to 100mg/kg. Columns packed with Fe-eZ were tested for As removal from water collected from acid mine drainage (AMD) and groundwater containing high natural organic matter and high As(III). With an initial concentration of 147 μg/L in the AMD water, a complete As removal was achieved up to 40 pore volumes. However, the Fe-eZ was not effective to remove As from Chia-Nan Plain groundwater due to its high initial As concentration (511 μg/L), high amounts of natural organic matter, as well as its low oxidation-reduction potential, under which the As was in reduced As(III) form.     

Calcium hydroxyapatites: evaluation of sorption properties for cadmium ions in aqueous solution

The efficiency and mechanisms of cadmium sorption on two synthetic calcium hydroxyapatites from aqueous solution were investigated. Both hydroxyapatites remove cadmium from aqueous solutions with an efficiency higher than 99.5% at pH 5–6.The mechanisms of cadmium sorption were studied using batch experiments, X-ray diffraction, scanning electron microscopy and nuclear microprobe. Cadmium is incorporated into the hydroxyapatite structure via diffusion and ion exchange. Once cadmium is sorbed, cadmium-containing hydroxyapatites can be separated from the liquid phase by flocculation. Thus hydroxyapatite can potentially be used for remediating contaminated water and industrial wastes. The fact that cadmium is incorporated into the bulk of the apatite is important in the context of the safe storage of used sorbent material.     

Oil spill cleanup from sea water by carbon nanotube sponges

Oil spills in the sea have caused many serious environmental problems worldwide. In this study, carbon nanotube (CNT) sponges were used to cleanup oil slicks on sea waters. This method was compared with two traditional representative sorbents, including polypropylene fiber fabric and woolen felt. The CNT sponges had a larger oil sorption capacity than the other two sorbents. The maximum oil sorption capacity (Q_m) of the CNT sponge was 92.30 g/g, which was 12 to 13.5 times larger than the Q_m of the other two sorbents (the Q_m of the polypropylene fiber fabric and woolen felt were 7.45 and 6.74 g/g, respectively). In addition, unlike the other two sorbents, the CNT sponge was super-hydrophobic and did not adsorb any water during oil spill cleanup. CNT sponges are potentially very useful for cleaning up oil spills from sea water.     

厦门地表水油污染的油种指纹鉴定

厦门地表水主要有从九龙江取水的北溪引水渠和坂头水库等,系厦门饮用水源。为保证自来水水质,自1989年至1994年开展厦门地表水水质调查,无论定期取样或临时抽样,早期均发现有石油烃污染。经带毛细管色谱柱的程序升温气相色谱作正构烷烃油种指纹鉴定,为船舶的柴油和汽车的机油、废油污染地表水。其中还检出如苯并(α)芘等多环芳香烃化合物,经美国罗得岛大学海洋研究生院有机地球化学实验室测定确认了这一结论。通过有关方面进行污染源治理,现水质得以恢复,自来水中苯并(α)芘已符合饮用水标准。     

Activated carbon adsorption of PAHs from vegetable oil used in soil remediation

Vegetable oil has been proven to be advantageous as a non-toxic, cost-effective and biodegradable solvent to extract polycyclic aromatic hydrocarbons (PAHs) from contaminated soils for remediation purposes. The resulting vegetable oil contained PAHs and therefore required a method for subsequent removal of extracted PAHs and reuse of the oil in remediation processes. In this paper, activated carbon adsorption of PAHs from vegetable oil used in soil remediation was assessed to ascertain PAH contaminated oil regeneration. Vegetable oils, originating from lab scale remediation, with different PAH concentrations were examined to study the adsorption of PAHs on activated carbon. Batch adsorption tests were performed by shaking oil-activated carbon mixtures in flasks. Equilibrium data were fitted with the Langmuir and Freundlich isothermal models. Studies were also carried out using columns packed with activated carbon. In addition, the effects of initial PAH concentration and activated carbon dosage on sorption capacities were investigated. Results clearly revealed the effectiveness of using activated carbon as an adsorbent to remove PAHs from the vegetable oil. Adsorption equilibrium of PAHs on activated carbon from the vegetable oil was successfully evaluated by the Langmuir and Freundlich isotherms. The initial PAH concentrations and carbon dosage affected adsorption significantly. The results indicate that the reuse of vegetable oil was feasible.     

Study of oil sorption behavior of filled and structured fiber assemblies made from polypropylene, kapok and milkweed fibers

This article reports on oil sorption behavior of fiber assemblies made up of single natural and synthetic fibers as well as blend of natural and synthetic fibers when tested with high density oil and diesel oil. A series of filled fiber assemblies were prepared from 100% polypropylene, kapok, and milkweed fibers and another series of bonded structured fiber assemblies were prepared from a 70/30 blend of kapok and polypropylene fibers and a 70/30 blend of milkweed and polypropylene fibers. It was observed that the porosity of the fiber assemblies played a very important role in determining its oil sorption capacity. The polypropylene fiber assembly exhibited the highest sorption capacity (g/g) followed by the kapok and milkweed fiber assemblies at porosity <0.98. At higher porosities (above 0.98), polypropylene filled fiber assembly has poor sorption capacity due to large sized inter fiber pore. The kapok and milkweed fibers have intra fiber porosities of 0.81 and 0.83, respectively. All the fiber assemblies showed higher oil sorption capacity with the high density oil as compared to the diesel oil. As the kapok and milkweed fiber have low cellulose content, hence their slow degradation is an advantage in fresh and marine water applications. The good sorption capacity of kapok and milkweed fiber assemblies along with their bio-degradable nature offer great scope for structuring them into fiber assemblies with large porosity and uniform pores to have efficient oil sorbents.     

二甲基硅油对中铬黄颜料的表面改性

为了提高中铬黄颜料在漆料中的分散性,采用包覆改性法,以二甲基硅油为改性剂对中铬黄颜料进行表面改性,通过研究表面改性对颜料的吸油量、流动性、沉降时间、傅里叶红外光谱、扫描电镜图像的影响规律,对改性机理进行探讨。结果表明,使用二甲基硅油对中铬黄颜料进行表面改性可改善其在干燥状态下和有机聚合物基体中的分散性,随着改性剂用量的增大,中铬黄颜料的每百克吸油量由原来的30 g减小为16 g;经过二甲基硅油表面改性处理后,中铬黄粉体在煤油中的沉降时间由1 h延长到16 h左右;最佳工艺条件是二甲基硅油的质量为中铬黄质量的2.5%;二甲基硅油与中铬黄颗粒的表面吸附方式为物理涂覆;经过表面改性处理后,颗粒在干燥状态下的分散性明显提高。     

Removal of nickel from aqueous solutions using crab shells

Partially converted crab shell waste, which contains chitosan, was used to remove nickel from water. The chelating ability of chitosan makes it an excellent adsorbent for removing pollutants. Advantages of chitosan in crab shells include availability, low cost, and high biocompatibility. The metal uptake by partially converted crab shell waste was successful and rapid. The sorption occurred primarily within 5 min. The sorption mechanism appears to be quite complicated and cannot be adequately described by either the Langmuir or Freundlich theories. Various anions, including chloride, bromide, fluoride, acetate, sulfate, nitrate, and phosphate, were found to have a very small effect on the capacity of the crab shells for uptake of nickel. The effect of pH was also found not to be prominent.     

An efficient calix[4]arene based silica sorbent for the removal of endosulfan from water

The present work explores sorption behavior of calix[4]arene based silica resin to remove α and β endosulfan isomers from aqueous solution. The efficiency of resin was checked through both batch and column sorption methods. In both methods, the sorption parameters, i.e. pH, equilibrium time, shaking speed and sorbent dosage were optimized as 2, 60 min, 125 rpm and 50 mg, respectively. Freundlich and Langmuir sorption isotherm models were applied to validate the sorption process. The data obtained in both models reveal that the sorption is favorable. Column sorption data were analyzed through Thomas model to calculate kinetic coefficient k(TH) and maximum sorption capacity q(o) of the resin, which were found to be 6.18 and 5.83 cm(3) mg(-1) min(-1) as well as 1.11 and 1.08 mg g(-1) for α and β endosulfan, respectively. Kinetics of sorption shows that it follows pseudo second order rate equation. The optimized method has also been applied to real water samples and the results show that calix[4]arene based silica resin is an effective sorbent to remove endosulfan from waste waters.     

Sorption Recovery of Strontium from Seawater

Sorption recovery of strontium from seawater and prospects of using selective sorbents for treatment of seawater or mixtures of liquid radioactive wastes (LRW) with seawater to remove ⁹⁰Sr are examined. A comparative analysis is made of characteristics of various sorbents. The most of the sorbents studied demonstrate low distribution coefficients and selectivity with respect to strontium, being unable to provide efficient removal of ⁹⁰Sr from seawater. The exceptions are new sorption reagents developed by the authors, which show promise for treatment of LRW to remove strontium. The possible mechanism of strontium sorption with these sorbents is suggested.     

Screening of new sorbent materials for cadmium removal from aqueous solutions

This study compares the abilities of four low-cost materials: peels of peas, broad bean, and medlar, respectively and fig leaves, to remove cadmium from aqueous solutions. Kinetic data and equilibrium sorption isotherms were measured in batch conditions. Kinetics of cadmium sorption was contact time, initial cadmium concentration and sorbent type dependent. The results also showed that the kinetics of cadmium sorption were described by a pseudo second-order rate model. The cadmium uptake of these low-cost materials was quantitatively evaluated using sorption isotherms. Results indicated that Langmuir model gave an acceptable fit to the experimental data. A high cadmium sorption was observed by these materials. The broad bean peel was the most effective to remove cadmium ions with a maximum sorption capacity about 147.71 mg/g followed by peas peel (118.91 mg/g), fig leaves (103.09 mg/g), and medlar peel (98.14 mg/g).