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Waste reuse and renewable energy generation are encouraged in many countries. Anaerobic digestion of sewage sludge is usually limited by the slow hydrolysis rate of the sludge. To resolve the problem the lime mud was used in this biomethane production. Batch tests were performed at 55 °C with lime mud concentrations ranging from 1.25 to 5.00 g/L. The results showed that the highest methane yield per gram of volatile solid and volatile solid reduction were 146 ml and 42.4% at lime mud concentration of 2.50 g/L, which were 1.77 and 3.01 times higher than that of the control tests without lime mud, respectively. However, high levels of lime mud reduced the amount of available substrate and inhibited the anaerobes, thereby decreasing the methane production. The modified Gompertz model showed a better fit for the results than the first-order model. It was also found that the eco-friendly treatment of two types of solid waste had the potential to synergistically contribute to waste reuse and energy recovery.

Lime mud from papermaking process (LMP) is a solid waste originated from the causticization process. Due to fine particle size and high alkalinity of LMP, its recovery is expensive and adverse effect is still uncertain. This review presents several current techniques proposed for LMP utilization in order to minimize its toxic effect on the environment. Conventional uses such as soil amendments, landfill and building materials are continually conducted. Recently, novel utilization of LMP to immobilize and remove pollutants in different phases (liquid, solid and gas) has provided new opportunities for efficient removal of dye, organics, heavy metals, carbon dioxide and sulfur dioxide. Moreover, as an additive summarized in this review, LMP can enhance the performance of biological process for treating organic waste, and its available value would be potentially improved further.

In this study, biochars were prepared from corn-bran residue (CBR) at a low pyrolysis temperature range from 300 to 600 °C. The CBR and CBR-derived chars were characterized and utilized to remove Cr(VI) from the aqueous solution. CBR-chars produced at higher temperatures have larger specific surface area and lower content of functional groups. The Cr(VI) removals by CBR and CBR-chars were mainly achieved by the reduction from Cr(VI) to Cr(III) through SO32− or oxygen-containing functional groups from these adsorbents. The amount of Cr(VI) removed by the adsorbents ranged from 8.18 to 86.49 mg g−1 at the initial Cr(VI) concentration range of 50–500 mg L−1 (pH 2). The SO32−-rich CBR was demonstrated to be more economical and effective for Cr(VI) removal than others, with a Cr(VI) removal efficiency of 96.02%. The results can be modeled by Freundlich isotherm at pH 2, indicating that the Cr(VI) adsorption process was complex and related with solution pH and adsorbent properties. Reduction-coupled with adsorption was the mechanism of Cr(VI) removal by CBR and CBR-derived chars.

The effects of lime mud from papermaking process (LMP) addition as buffer agent and inorganic nutrient on the anaerobic digestion stability of food waste (FW) were investigated under mesophilic conditions with the aim of avoiding volatile fatty acids accumulation, and inorganic elements deficiency. When LMP concentration ranged from 6.0 to 10g/L, the FW anaerobic digestion could maintain efficient and stable state. These advantages are attributed to the existence of Ca, Na, Mg, K, Fe, and alkaline substances that favor the methanogenic process. The highest CH4 yield of 272.8mL/g-VS was obtained at LMP and VS concentrations of 10.0 and 19.8g/L, respectively, with the corresponding lag-phase time of 3.84d and final pH of 8.4. The methanogens from residue digestates mainly consisted of Methanobrevibacter, coccus-type and sarcina-type methanogens with LMP addition compared to Methanobacteria in control. However, higher concentration of LMP inhibited methanogenic activities and methane production.

Cryogenic-treated inserts (CTIs) are playing a vital role in the significant improvement of tool life and the enhancement of mechanical properties of the cutting tools during conventional machining process. This work addressed the upshot of cryogenic treatment of physical vapor deposition TiAlN/NbN-coated carbide insert on the machinability of a Ti-6Al-4V alloy workpiece. It is weighed in terms of surface roughness, chip morphology, and tool wear in the cutting tool insert. Surface roughness was measured by a noncontact type 3-D laser scan microscope system. The observed average surface roughness in CTI reduction is between 13 and 32 % over that of the untreated insert (UTI) machining condition. The multisurface chip characteristics of free surface and back surface were identified and broken down by scanning electron microscopy. The experimental results demonstrated that the favorable chips and the reduction in tool wear were better achieved under the CTI machining condition than under the UTI machining condition.