Leather Sludge Research Articles

Study on preparation and properties of the leather sludge wrap shell aggregate by non-burning method

The leather sludge was used as raw material to prepare non-burning sludge wrap shell aggregate by the non-burning method. The effects of different processes on the cylinder compressive strength, water absorption rate, and frost resistance of the non-burning wrap shell aggregate were discussed, through the research on the wrap shell amount, core component, and curing age of the non-burning wrap shell aggregate. The entropy method was used to determine the best process of sludge wrap shell aggregate, and the solidification effect of the shell wrapping process on sludge heavy metal Cr+6 was evaluated and analyzed. The results show that with the increase of curing age, the cylinder compressive strength of wrap shell aggregate increases first and then stabilizes, the water absorption rate decreases gradually, and the frost resistance is significantly enhanced until the 28d of curing age. The more the wrap shell amount and the less the sludge content in the core component is, the higher the cylinder compressive strength, the lower the water absorption, and the better the frost resistance of the wrap shell aggregate are. The entropy method, finally determined the optimal shell wrapping process to be sludge: cement: slag = 50%: 25%: 25%, the wrap shell amount was 25g/100g, and the curing age was 28d. The composite cementitious system and the shell wrapping process can inhibit and effectively reduce the leaching of heavy metals Cr+6 from the sludge wrap shell aggregate by more than 80%.

Graphene oxide reinforced nanocellulose/leather waste-based biopolymer nano compounds for possible bioenergy production

In this study, a blend of graphene oxide (GO), leather waste (leather sludge(LS)/leather fleshings (LF)), nanocellulose (nano-C) (biopolymer), and glycerol (Gly) homogeneously in alkaline aqueous solution is used to produce biopolymer blended solution (BBS), by chemical polymerization, for use in bioenergy. The efficient and eco-friendly BBS was characterized by its physicochemical and electrical conductivity properties. The BBS achieved the highest current density energy value (0. 53 mA cm-2) at 1. 2 V. The results of the research show the significance of evaluating bioenergy technological environmental performance from comparable perspectives to examine and identify environmental exchange from existing bioenergy developments.

Heavy metal accumulation and mobility in a soil profile depend on the organic waste type applied

While organic waste amendments can initially improve soil physicochemical properties, including nutritional benefits to plants and increased microorganism activity, long-term application of excessive amounts of organic wastes can cause accumulation of heavy metals (HMs). Thus, the current study examined the accumulation of HMs in agricultural soil profiles following organic waste application. Three common organic sludge, including municipal sewage sludge (MSS), industrial sewage sludge (ISS), and leather sludge (LS), were applied annually to an agricultural soil under field conditions over 7 years (1994–2000) at a rate of 25 and 50 t ha−1 year−1. Subsequently, when organic sludge amendments were ceased, the experimental plots were cultivated without any treatments for another 12 years (2001–2012) and the changes in HM concentrations along the soil depth profile were monitored together with soil pH, dissolved organic carbon (DOC), and dehydrogenase activity (DHA). Significant increases in Cu, Pb, and Zn concentrations were observed down to a depth of 80 cm in soils treated with ISS and LS, where sludge application also increased the levels of Cd, Cr, Pb, and Zn and their movement down the soil profile. However, with the exception of Cu, no significant changes in HM concentrations were observed following treatment with MSS. At a depth of 80 cm, soils which had received 25 and 50 t ha−1 LS showed, respectively, 4 and 14 times higher Cr levels than the control soil. Organic sludge induced changes in soil pH and soil DOC concentration which were the key factors influencing HM movement and accumulation following organic sludge treatment.

Synthesis and characterization of black ceramic pigments by recycling of two hazardous wastes

In this study, two different industrial wastes, namely vanadium tailing and leather sludge, were used as less expensive alternative raw materials for the synthesis of black ceramic pigments to be used in commercial glazes. The pigments were based on hematite structure (FexCr1-x)2O3 and prepared by the common solid-state reaction method, under optimal formulation and processing conditions. The synthesized pigments were characterized in typical ceramic glazes and ceramic tile bodies. Optimal color development was achieved when the Fe/Cr mole ratios were 2.0 with 40 wt% content of vanadium tailing at 1200 °C. The coloring properties were similar to those imparted by a commercial black pigment.

Synthesis of black pigments containing chromium from leather sludge

The black ceramic pigments with spinel structure have been prepared by using Cr-rich leather sludge in this paper. The washed Cr-rich leather sludge calcined at 1100°C for 1h as chromium oxide precursor (named as CA) was mixed with an appropriate proportion of other industrial metallic oxides, followed synthesizing black ceramic pigment by sintering. Both non-washed and washed sludge fired at 1100°C were characterized by X-ray fluorescence (XRF) in order to determine their chemical compositions and X-ray diffraction (XRD) analysis to confirm that CA mainly contains Cr2O3 crystal phase. The results show that CA could be used as a source of chromium to prepare black pigment. The crystalline phases of obtained pigments were characterized by XRD. Furthermore, the morphology as well as the composition of pigments was investigated by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The color coordinates of pigments were examined and compared with the commercial pigments based on CIE-L* a* b* values measured using UV–vis spectroscopy. The obtained pigments sintered at 1200°C with 35–55wt% content of CA possess the excellent black spinel structure and color effect. Under optimized conditions, the pigment has low average spectral reflectance (7%).

Effect of Cow Manure and Saw Dust as the Additive Materials for Efficient Vermistabilization

The influence of additive materials including saw dust and cow manure in the ripening of leather sludge for the efficient vermisabilization was studied. The ripening characteristics of the leather sludge, the growth of earthworms in the growth bed and the by-products like cast were observed according to the mixing ratio of additive materials. When the mixed leather sludge of which the additive materials contents were over 20% were ripened for 50 days, the values of ORP and alkalinity were changed to the favorable ranges for earthworms, the positive (+) and below 1,000 mg/l as CaCO₃, respectively. The velocity of ripening improving the characteristics of the leather sludge was faster in the sludge mixed with cow manure than saw dust. This results could also be verified from the monitoring of the states of earthworm growth using the survival rate, the increase rate of lifeweight and the hatching rate of earthworm cocoon in the their growth bed packed with the ripened sludge. The values of CEC in cast, the vermi-stabilized sludge, were increased with the mixing ratio of additive materials, but the content of heavy metals was drcreased by the dilution effect and accumulation in the earthworm body. Above results show that the leather sludge might be efficiently stabilized by earthworms through the ripening for 50 days using additive materials. Cow manure can be used as a good additive materials for leather sludge as much as saw dust, and the optimum content of additive materials in the well-ripened leather sludge was about 30%.

Dose–mortality assessment upon reuse and recycling of industrial sludge

This study provides a novel attempt to put forward, in general toxicological terms, quantitative ranking of toxicity of various sources of sludge for possible reusability in further applications. The high leaching concentrations of copper in printed circuit board (PCB) sludge and chromium in leather sludge apparently exceeded current Taiwan's EPA regulatory thresholds and should be classified as hazardous wastes. Dose–mortality analysis indicated that the toxicity ranking of different sources of sludge was PCB sludge > CaF 2 sludge > leather sludge. PCB sludge was also confirmed as a hazardous waste since the toxicity potency of PCB sludge was nearly identical to CdCl 2. However, leather sludge seemed to be much less toxic than as anticipated, perhaps due to a significant decrease of toxic species bioavailable in the aqueous phase to the reporter bacterium Escherichia coli DH5α. For possible reusability of sludge, maximum concentrations allowable to be considered “safe” (ca. EC 100/100) were 9.68, 42.1 and 176 mg L −1 for CaF 2 sludge, PCB sludge and leather sludge, respectively.