Potential of ash from agricultural waste as substitute of commercial FeCl3 in primary treatment of landfill leachate

Due to the ever increasing global population, higher volumes of industrial waste discharges to landfill have caused major problems for the environment. This study investigated the performance of rice straw ash (RSA) as a natural coagulant under different conditions for the treatment of landfill leachates by coagulation-flocculation and microfiltration, with and without addition of FeCl3. The highest performing treatment conditions (RSA = 2.48 g/L, FeCl3 = 4.98 g/L, settling time = 54.75min) were achieved with the combined use of RSA and FeCl3 as coagulant and led to a sludge volume index of 41.65 mL/g, 51.27% COD removal and 76.48% total suspended solid removal. In contrast, FeCl3 alone achieved slightly better COD and total suspended solid removal rates, however it resulted in higher sludge volume index and sludge production. The combined use of RSA and FeCl3 reduced the consumption of these two coagulants by 78.76% and 46.69% respectively. Functional groups and thermal stability of the flocs showed that RSA + FeCl3 synergistically enhance the mechanisms of the coagulation-flocculation process, including adsorption by particle's bridging, charge neutralization and size of flocs. Combining the coagulants resulted in increased van der Waals forces and lower attractive forces of the inter-colloidal energy barrier in the leachate. Additionally, the highest and lowest heavy metals removal rates for treatment by microfiltration were found for Fe (92.15%) and Mg (7.63%), with a total heavy metals removal efficiency in the range of 6.08-90.78%. The findings of this study show that RSA can serve as a natural eco-friendly coagulant both alone and in combination with FeCl3 in the leachate treatment.

Effect of integrating industrial and agricultural wastes on concrete performance with and without microbial activity

Cement is an essential material used in constructional activities. An emerging concern in the industry however is the CO₂ emissions, which are triggered by cement manufacturing units. These emissions can be controlled to some extent by not using cement exclusively and instead replacing a percentage of it with waste material with properties similar to cement. Electric arc furnace dust (EAFD) and rice straw ash (RSA) are waste materials from industrial and agricultural sources which also contain similar constituents that are present in cement. Thus, the objective of this study is to check the effect of EAFD and RSA on concrete properties with the application of Aspergillus niger and Bacillus megaterium. Taguchi's design of experiments has been utilised to explore the effect of operating parameters (i.e. EAFD and RSA replacement (5%, 10% and 15%), curing period of concrete cubes (7, 14 and 28 days) and cell count of fungus/bacteria (10⁴, 10⁶ and 10⁸ CFU/ml)) on the compressive strength and water absorption capacity of concrete blocks in three different scenarios. Optimisation has then been carried out by using the multi-objective genetic algorithm to evaluate the maximum performance of concrete. However, the results of the study indicate best performance in the 2nd context where dust replacement, curing time and cell count were 5%, 18 days and 9.39 × 10⁷ cells per ml of water, respectively, for concrete production utilising Aspergillus niger.

Evaluation of water absorption and chloride ion penetration of rice straw ash and microsilica admixed pavement quality concrete

The effects of rice straw ash (RSA) and microsilica (MS) on durability properties (water absorption and chloride ion penetration) of M40 grade Pavement Quality Concrete (PQC) were studied. Ten concrete samples were prepared by partially substituting cement with RSA and MS in various proportions. A significant reduction was observed in the water absorption and chloride ion penetration in concrete samples with an increase in the curing age as well as with an increase in the proportion of MS and RSA. The maximum reduction in water absorption and chloride ion penetration was observed in R2M3 (10% RSA and 7.5% MS) as compared to control concrete (R0). The analytical relationships were developed between the above-mentioned parameters and curing age of concrete. A linear equation was established between the initial and secondary rate of water absorption of concrete and also between the chloride ion penetration of concrete at 10–20 mm and 25–35 mm depth. Both these equations were applicable to all the concrete samples of this study. Predictive charts were generated between the above-mentioned parameters and days of curing in water.

Bioactive mesoporous wollastonite particles for bone tissue engineering

The current investigation was aimed at identifying the role of mesoporous wollastonite particles on the healing of rat tibial bone defect. The bone defect was created with a 3-mm-diameter dental drill, and it was filled with mesoporous wollastonite particles. After second and fourth weeks of filling treatments, it was found that mesoporous wollastonite particles promoted bone formation as evidenced by X-ray, histological, scanning electron microscope, and energy-dispersive spectra studies. X-ray study showed the closure of drill hole as seen by high-dense radio-opacity image. Histological analysis depicted the deposition of collagen in the bone defect area in response to mesoporous wollastonite particles’ treatment. Scanning electron microscope–energy-dispersive spectra analyses of the sectioned implants also identified the deposition of apatite by these particles. Thus, our results suggested that mesoporous wollastonite particles have bioactive properties, and they can be used as a suitable filling material for promotion of bone formation in vivo.