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A machine learning model for microwave-assisted pyrolysis technology was developed in this study. The data set of 112 unique experiments was created by analysing the published literature based on biochar. The linear, interactive and quadratic regression models were trained with the selected data set. Out of three regressions models, the quadratic model $${\text{Biochar Yield}} = - 601.78 + 17.336 \times {\text{VM}} + 25.338 \times {\text{AC}} - 0.26367 \times T - 0.293 \times {\text{VM}} \times {\text{AC}} - 0.10305 \times {\text{VM}}^{2} - 0.1893 \times {\text{AC}}^{2} + 1.59 \times 10^{ - 3} \times T^{2}$$ was found to have highest R2 value of 0.894. The predicted model developed based on the data from literature was validated with laboratory experimental results. Prediction and validation results showed that data prediction can be a useful tool for the preview of selected feedstock and process parameters. Volatile matter, ash content and temperature were found to be the prominent factors in the trained model. Biochar yield was predicted with a minimum root mean square error of 7 when validated with experimental results. Thus, the predicted model can be used as empirical equation for future experiments to predict biochar yield.

Microalgal biofuel production is a useful process to produce sustainable and carbon-neutral biofuels. The choice of microalgal species and the processes adopted in various production stages determine biofuel production. In this review, recent technological advancements made in various stages of microalgal biofuel production are discussed. This review also discussed the recent progress made in harvesting microalgal biomass and lipid extraction. In addition, the viability of using wastewater as a nutrient source for microalgae and its nutrient removal capabilities has been discussed in detail. This is the first study that enlists and compares the minimum achievable cost of biofuel produced in different studies. Also, process optimization strategies adopted to minimize the cost are discussed. The reported biofuel production cost varied from 0.14 $/L to 24.33 $/L based on the variation in the microalgae strains, production method, and optimization strategies.

In recent years, microwave (MW) photocatalytic treatment was used for the removal of several pollutants from wastewater to overcome the disadvantages of conventional photocatalytic treatment. MW irradiation significantly enhanced the photocatalytic degradation pollutants and is considered an innovative treatment approach. This enhancement in photoactivity was mainly attributed to thermal and non-thermal effects of the MW irradiation. Even though the thermal effects of MW irradiation have been conclusively studied, there are many conflicting results regarding the non-thermal effects in catalysts. In general, it has been verified that the non-thermal effects are due to the electrical and magnetic properties of MW. In this article, a detailed review of the recent advancements in MW-assisted photocatalysis has been done, emphasizing the non-thermal effects of MW radiation on the surface of the catalysts. Also, the evolution of external ultraviolet (UV) sources from the conventional Hg lamp to the latest microwave-driven electrodeless lamps (MDEL) has been discussed. MW photocatalytic treatment using MDELs showed complete removal of lignin, dimethyl phthalate (DMP), and azo dye reactive brilliant red X-3B (BR) and more than 90% removal for cimetidine (CMT), rhodamine B (RB), and methylene blue (MB). A brief comparison regarding the removal efficiencies of pollutants by various AOPs and MW photocatalysis has been made to understand the enhanced photoactivity. In addition, various operating parameters that affect the MW photocatalysis like MW intensity, pH, dissolved oxygen, and catalyst dosage; the degradation pathways of various pollutants; and the cost assessment of MW photocatalysis are discussed in detail. This paper will deliver a scientific and technical overview and useful information to scientists and engineers working in this field.

In this study, simultaneous nitrification and denitrification-sequencing batch reactor (SND-SBR) process was investigated to treat greywater. The effect of three process parameters, including hydraulic retention time (HRT), volumetric exchange ratio (VER) and sludge retention time (SRT), was optimised using a 2

The continuous growth of the pharmaceutical drug industry has escalated the problem of pharmaceutical waste disposal, and subsequent contamination of aquatic bodies. Paracetamol is one of the most prescribed and purchased drugs that has been widely detected in wastewater and surface water. The present study investigated paracetamol degradation by photocatalytic treatment in a batch system using TiO2 supported on aluminosilicate recovered from waste LED panel (ATiO2). The prepared ATiO2 catalyst was characterized for morphology, elemental composition and crystallinity using scanning electron microscope (SEM) with electron dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. ATiO2 was spherical in morphology with a predominance of the anatase phase of TiO2 and an average size of ∼15 nm. Subsequently, the effects of operating parameters, viz., initial paracetamol concentration (1–10 mg/L), catalyst dosage (0.5–4.0 g/L) and pH (4–10) on paracetamol degradation were investigated using central composite design (CCD). A polynomial model was developed to interpret the linear and interactive effect of operating parameters on the paracetamol degradation efficiency. About 99% degradation efficiency of paracetamol was obtained at optimum conditions (Initial paracetamol concentration ∼2.74 mg/L, ATiO2 dosage ∼2.71 g/L and pH ∼ 9.5). The mechanism of paracetamol degradation was adsorption on aluminosilicate and subsequent degradation by TiO2. ATiO2 could be effectively reused up to 3 cycles, with

Burning of agricultural waste like crop residues releases black carbon, a major source of air pollution in megacities like Delhi. Conversely, crop residues are a rich source of cellulose, hemicellulose, and lignin. The present study investigated the effect of heating time (HT) and MW power (P) on biochar yield from rice husk, an agricultural waste, using microwave pyrolysis. Biochar yield varied from 68% (HT 18 min and P 500 W) to 39% (at HT 15 min and P 900 W). A second-order polynomial model was obtained for predicting biochar yield, which signified that microwave power and interaction of heating time and microwave power positively affected the maximum yield of biochar. The high heating value and fuel ratio of biochar (25.46 MJ/kg and 2.82) showed improvement compared with that of rice husk (12.43 MJ/kg and 0.06). Also, the MW pyrolysis of rice husk resulted in increased fixed carbon content from 4.78% in rice husk to 52.2% in biochar. The property of rice husk and biochar indicated a decrease in O/C ratio from 1.5 to 0.66, improvement in surface area from 2.4 to 190 m2/g, and an increase in pH from 6.71 to 8.75. Also, energy density and energy yield in MW pyrolysis were found as 1.46 and 99.28% respectively. Hence, MW pyrolysis of rice husk resulted in a high quality of biochar that could be used as a potential source of energy, nutrient captive media, and soil amendment.

Microwave-assisted pyrolysis (MAP) is considered as one of the improved biochar production options given its cost efficiency, efficient heat transfer and better-quality control. Researchers have observed that biochar can be considered as an alternative erosion control material due to its high porosity, surface area, and surface functional groups. However, as per the available literature, contradictions exist regarding some erosion control mechanisms of biochar with respect to water holding capacity (WHC), bulk density, and aggregate formation. Further, there is a lack of exploration as to how biochar produced using MAP can be adopted for erosion control. The objective of this study is to critically review existing literature on the usage of biochar for erosion control in various types of soils. In addition, the use of the MAP technique for producing biochar for erosion control is explored. Based on the review, the available experimentation research is generally of short duration with the least consideration of the long-term ageing effects of biochar. The studies on erosion control using biochar have been mostly conducted in the shallower zone (i.e., within 20 cm). The effect of different types of biochars on various soils does not seem to have been investigated systematically. It has been observed that the mechanism of washing away biochar particles and nutrients is rarely taken into account while measuring erosion. Further, the comparative analysis of biochar types produced from various feedstocks, including their physiochemical properties, is rarely explored for their applications in soil erosion. This study aims to critically analyze available literature for the erosion suppressing mechanism of biochar, limitations and the feasibility of microwave-assisted biochar production for the purpose of soil erosion control.

Green synthesized TiO2 (CG-TiO2) was prepared from Titanium isopropoxide (TTIP) precursor using aqueous leaf extract of Calotropis gigantea (CG). The CG-TiO2 was prepared with different mi...

The present study investigated the solar photocatalytic treatment of greywater using modified TiO2 catalysts, viz., M-TiO2, U–TiO2, NP-TiO2, and NT-TiO2 synthesized through ultrasonication, microwave, and sol-gel method with/without doping respectively. X-ray dispersive spectroscopy (XRD) results indicated a negligible change in the crystallinity of the modified catalysts compared to commercial TiO2 catalyst, Degussa P-25 (P-25). Scanning electron microscopy (SEM) analysis depicted the lowest particle size of 88.89 nm for U–TiO2. The calculated band gap energy for P-25, U–TiO2, M-TiO2, NP-TiO2, and NT-TiO2 were 3.65, 3.1, 3.5, 3.35, and 2.7 eV, respectively. The mineralization efficiency was in the order of NT-TiO2>U–TiO2>NP-TiO2∼M-TiO2>P-25, with the highest mineralization efficiency of about 75% within 3 h using NT-TiO2. The nitrate removal was in the order of NT-TiO2>U–TiO2∼NP-TiO2>M-TiO2>P-25, with the nitrate removal of 92.5%. Simultaneous oxidation of organic matter and reduction of ammonia were observed during the solar photocatalytic treatment of greywater. The comparison of sunlight NT-TiO2system with other photocatalytic treatment employed for greywater reveals that the NT-TiO2 system was highly energy efficient (∼31.86 kWh (kgCOD)−1) compared to other systems.

The present study investigated the potential tertiary treatment of wastewater by adsorption using rice husk biochar (RHC) obtained from microwave pyrolysis of rice husk. Adsorption experiments with RHC indicated phosphate and nitrate adsorption of 65% and 75% respectively. The adsorption kinetics indicated pseudo-second-order adsorption model for adsorption of nutrients on biochar with an R2 value more than 0.98. In addition, the Langmuir-Freundlich isotherm was observed to represent the adsorption of phosphate on RHC, whereas adsorption data of nitrate depicted Langmuir isotherm followed by Temkin and Dubinin-Radushkevich isotherms. The maximum phosphate and nitrate adsorption capacity were 71 mg/kg and 497 mg/kg respectively using Langmuir isotherm model. The desorption study indicated a release of 96.6% and 44.4% of adsorbed phosphate and nitrate, respectively. Hence, from 1 kg of nutrient loaded RHC about 68 mg of phosphate and 220 mg of nitrate can be extracted for land application.

The present study investigated the photolytic and photocatalytic treatment of soft drink industry wastewater (SDIW) in presence of microwave (MW) irradiation. The treatment efficiency was investigated in terms of removal rate of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphate (TP) in microwave photolysis (MWP) system, MW photocatalytic system with one and two electrodeless discharge lamp (EDL), denoted as MWPC-1 and MWPC-2 respectively. The MWPC-2 system showed highest efficiency with a COD, TKN and TP removal rate of 7.48, 82.5 and 0.63 mg/L/min respectively. The COD removal was achieved by direct interaction MW and UV with organics. The photocatalytic oxidation of NH3 to nitrite and nitrate at catalyst surface cause TKN removal from SDIW. On the other hand, major route of TP removal was phosphate reduction occurred in the aqueous phase. On the other hand, the desorption study performed with the catalyst used in the MWPC experiments indicated a TP concentration