Adsorption of 2-nitrophenol using rice straw and rice husks hydrolyzed by subcritical water

Dynamic adsorption of 4-nitrophenol over shaped activated carbon produced from agriculture stones through microwave-assisted technique

The aim of current work is to develop the uptake of 4-nitrophenol from the liquid phase in a dynamic system by the shaped activated carbon produced through the microwave-assisted technique. The emphasis of research is to understand the effects of production factors on the performance of adsorbents in the dynamic adsorption. Hence, the phosphoric acid ratio, microwave irradiation power, carbonization temperature, and time were changed to identify the suitable conditions for the fabrication of granular and rod-like beds from the cherry, and date stones. It was found that the stone structure and H3PO4/waste ratio significantly affect the adsorption efficiency. The proper acid/waste ratio was determined to be 1.43, and 1.80 for the activation of cherry and date stones to achieve the maximal efficiency in which the power should be fixed at the levels of 600 and 400 W respectively. The equilibrium efficiency increases with the rise in carbonization temperature and time which should be controlled exactly to reach the maximal adsorption capacity, ~ 45 mg g-1 according to the Langmuir isotherm. Owing to the high specific surface area of shaped adsorbents, 350-450 mg g-1, the fabricated beds indicated the appropriate performance for the uptake of nitrophenol due to development of micropores, < 2 nm, in the framework of activated carbon.

Rice husk ash as a sustainable and economical alternative to chemical additives for enhanced rheology in drilling fluids

Performance evaluation of drilling fluids is essential for a successful drilling project, as they not only remove drill cuttings but also prevent undesired penetration or outflow of formation fluids by sealing off wellbore walls. However, concerns have been raised about the use of chemical additives in drilling fluids due to their toxicity and non-biodegradability. To this end, agricultural waste materials are recognized as a promising alternative as they are cost-effective, environmentally sustainable, and can be used as a substitute for lost circulation materials. Rice husk ash (RHA) has become popular as an additive due to its renewable characteristics, including its large surface area, silica content, and microporous structure. This research article explores the rheological properties of drilling fluid with RHA as a filter control medium. The results showed that increasing concentrations of RHA in the drilling mud significantly improved its rheology, particularly at higher concentrations (15 and 20 wt.%). The addition of RHA modified the filtration and rheological properties of the drilling mud, resulting in improved plastic viscosity, yield point, density, gel strength, and thixotropy. However, filter loss and mud cake thickness increased at elevated RHA concentrations. Furthermore, the pH test revealed that the mud's properties shifted toward the acidic region as the RHA concentration increased. The results indicate that RHA could be used as a sustainable and cost-effective alternative to conventional chemical additives with a positive environmental impact. This study may also provide valuable insights into the use of RHA in water-based bentonite mud and could serve as a guide for future research in the drilling industry.

Preparation of esterified biomass waste hydrogels and their removal of Pb2+, Cu2+ and Cd2+ from aqueous solution

The treatment of polluted water is a serious environmental problem in the world. Biomass is easily modified and can be prepared into adsorbent materials, which is expected to solve the problem of heavy metal ion adsorption in sewage. In this paper, esterified tobacco straw based hydrogels (ETS-PAA) were synthesized from waste tobacco straw biomass. The structure and thermal stability of these hydrogels were characterized by FTIR, SEM, EDS, XPS and TG. The adsorption of metal ions by the hydrogel was measured by ICP-MS. The effects of initial ion concentration, adsorption time, pH, and temperature on the heavy metal adsorption were investigated. The results showed that ETS-PAA possessed more pores, which led to a better adsorption capacity. The maximum adsorption amounts of Pb²⁺, Cu²⁺ and Cd²⁺ were 2.41 mmol·g^-1, 1.93 mmol·g^-1 and 1.77 mmol·g^-1, respectively. Finally, the adsorption mechanism and kinetics were analyzed. The adsorption was mainly accomplished by ion exchange of -COOK on the monomer chain with heavy metal ions, coordination of -OH and -CONH with heavy metal ions and interaction of ester bond, -COOH with heavy metal ions. The adsorption process was in accordance with the pseudo-second-order kinetic model and Freundlich model. The adsorption process belonged to multilayer chemisorption. This work shows that ETS-PAA was a promising material for the removal of heavy metal pollutants from aqueous solution.

Pine bark crosslinked to cyclodextrin for the adsorption of 2-nitrophenol from an aqueous solution

Adsorbents that are less expensive and more effective at removing organic micropollutants from wastewater have been developed through several approaches. Pine bark was treated with sodium hydroxide and then cross-linked to cyclodextrin using hexamethylene diisocyanate, in this study as an efficient adsorbent in the removal of 2-nitrophenol. FTIR, TGA and pHpzc analysis were used to characterize the biosorbent. The effects of pH, adsorbent mass, contact time and initial concentration on 2-nitrophenol removal was examined through batch adsorption studies. Pine bark crosslinked to cyclodextrin (PB-CD) surface functionalities was confirmed by FTIR analysis. It was discovered that solution pH, adsorbent mass, concentration and contact time all played a crucial role in the 2-nitrophenol uptake on PB-CD biosorbent and pine bark (PB) treated with sodium hydroxide. 2-Nitrophenol equilibrium was achieved with 0.05 g of adsorbents, with an initial concentration of 100–200 mg/dm3 at pH 5 after 60 min. The pseudo-second-order kinetic model and the Langmuir isotherm model significantly fitted the adsorption process. The Langmuir maximum capacities for PB and PB-CD were 47.36 mg/g and 77.82 mg/g, respectively. Overall, in the removal of 2-nitrophenol from an aqueous solution, PB-CD biosorbent is more cost-effective and efficient, in comparison with previously reported biosorbents in literature.

The evaluation of the performance of rice husk and rice straw as potential matrix to obtain the best lipase immobilized system: creating wealth from wastes

India generates 126.6 and 42 million tons of Rice straw (RS) and Rice husk (RH) annually, respectively. These agro-processing wastes feedstock are dumped in landfills or burnt, releasing toxic gases and particulate matter into the environment. This paper explores the valorization of these wastes feedstock into sustainable, economic products. We compare these wastes as matrices for lipase immobilization. These matrices were characterized, different parameters (pH, temperature, ionic strength, and metal ion cofactors) were checked, and the selected matrix was analyzed for reusability and hydrolysis of vegetable oils. Lipase immobilized Rice straw (LIRS) showed the highest activity with 72.84% protein loading. Field emission scanning electron microscopy (FESEM) demonstrated morphological changes after enzyme immobilization. FTIR showed no new bond formation, and immobilization data was fitted to Freundlich adsorption isotherm (with K = 12.18 mg/g, n_F = 4.5). The highest activity with protein loading, 91.05%, was observed at pH 8, 37 °C temperature, 50 mM ionic strength, and lipase activity doubled in the presence of Mg²⁺ ions. The LIRS retained 75% of its initial activity up to five cycles and efficiently hydrolyzed different oils. The results reflected that the LIRS system performs better and can be used to degrade oily waste.

Adsorption of basic fuchsin using soybean straw hydrolyzed by subcritical water

The valorization of agro-industrial residues can be improved through their full use, making the production of second-generation ethanol viable. In this scenario, hydrolyzed soybean straw generated from a subcritical water process was applied to the basic fuchsin adsorption. At pH eight, a high adsorption capacity was obtained. The mass test results showed that basic fuchsin's removal and adsorption capacity could be maximized with an adsorbent dosage of 0.9 g L-1. The linear driving force model was suitable for predicting the kinetic profile, and the kinetic curves showed that equilibrium was reached with only 30 min of contact time. Besides, the Langmuir model was the best to predict the adsorption isotherms. The thermodynamic parameters revealed a spontaneous and endothermic process. At 328 K, there is maximum adsorption capacity (72.9 mg g-1). Therefore, it can be stated that this material could be competitive in terms of adsorption capacity coupled with the idea of full use of waste.

Green production of hydrochar nut group from waste materials in subcritical water medium and investigation of their adsorption performance for crystal violet

This study evaluates the production of hydrochars from the outer shells of the nut group (peanut, hazelnut, walnut, and pistachio) in an eco-friendly subcritical water medium (SWM) and their effects as adsorbents on the removal of crystal violet (CV) from an aqueous solution. The prepared hydrochars were characterized using Brunauer Emmett-Teller (BET) analysis, scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), and zeta potential. The adsorption process was optimized based on pH, adsorbent dose, dye concentration, and contact time. The hazelnut hydrochar was found to have the maximum removal efficiency (91%). Optimum conditions were pH of 8, particle size <45 μm, adsorption time of 60 min, and dye concentration of 25 mg/L. The results of all hydrochars were fitted to the second-order kinetics. Langmuir, Freundlich, and Redlich-Peterson isotherms models were used to explain the relationship between adsorbent and adsorbate. For all hydrochars, CV adsorption was found to be feasible and inherently spontaneous. The use of materials with no commercial value like; the outer shells of the nut group, is considered a method for waste reduction using the SWM method. PRACTITIONER POINTS: Hydrochars of nut group were synthesized in the subcritical water medium. Adsorption ability of the hydrochars in the adsorption of crystal violet were investigated. Adsorption isotherms were used to explain the relationship between adsorbent and adsorbate. The hazelnut hydrochar provided the maximum removal efficiency (91%). Hazardous water pollutant effectively removed using an eco-friendly method.

Theoretical study and analysis of o-nitrophenol adsorption using layered double hydroxides containing Ca-Al, Ni-Al and Zn-Al

A theoretical assessment of the o-nitrophenol adsorption on layered double hydroxides containing different metallic species (Ca-Al, Ni-Al and Zn-Al) was performed. Experimental o-nitrophenol adsorption isotherms obtained at different adsorption temperatures with these layered double hydroxides were analyzed using a statistical physics monolayer model. Model calculations showed that the o-nitrophenol aggregation could occur with a high degree. It was estimated that the o-nitrophenol adsorption implied a non-flat orientation on all adsorbent surfaces and this process was multi-molecular. It was also demonstrated that there was no significant difference on the o-nitrophenol adsorption capacities of tested adsorbents, which varied from 77 to 135, 95 to 122 and 74 and 130 mg/g for Ca-Al, Ni-Al and Zn-Al layered double hydroxides, respectively. This finding suggested that the incorporation of Ca-Al, Ni-Al and Zn-Al in the layered double hydroxide structure played a similar role to adsorb o-nitrophenol molecules from aqueous solution. Calculated adsorption energies and thermodynamic functions confirmed an exothermic adsorption with the presence of physical-based interaction forces. This paper highlights the importance of reliable theoretical calculations based on statistical physics theory to contribute in the understanding of the adsorption mechanisms of a relevant water pollutant using layered double hydroxides as promising adsorbents for industrial applications.

Novel biochar and hydrochar for the adsorption of 2-nitrophenol from aqueous solutions: An approach using the PVSDM model

Two new adsorbents, namely avocado-based hydrochar and LDH/bone-based biochar, were developed, characterized, and applied for adsorbing 2-nitrophenol. The pore volume and surface diffusion model (PVSDM) was numerically solved for different geometries and applied to interpret the adsorption decay curves. Both adsorbents presented interesting textural and physicochemical characteristics, which achieved maximum adsorption capacities of 761 mg/g for biochar and 562 mg/g for hydrochar. The adsorption equilibrium data were well fitted by Henry isotherm. Besides, thermodynamic investigation revealed endothermic adsorption with the occurrence of electrostatic interactions. PVSDM predicted the adsorption decay curves for different adsorbent geometries at different initial concentrations of 2-nitrophenol. The surface diffusion was the main intraparticle mass transport mechanism. Furthermore, the external mass transfer and surface diffusion coefficients increased with the increase of 2-nitrophenol concentration.

Green synthesis of Quercus coccifera hydrochar in subcritical water medium and evaluation of its adsorption performance for BR18 dye

In this study, we investigated the production conditions of Quercus coccifera hydrochar, which is an inexpensive and easy available adsorbent, for the adsorption of Basic Red 18 (BR18) azo dye. The hydrochar was produced in the eco-friendly subcritical water medium (SWM). The effects of the pH (2-10), adsorbent size (45-106 μm), adsorbent dose (0.5-1.5 g/L), dye concentration (40-455 mg/L), and contact time (5-120 min) were studied via optimization experiments. The optimum conditions were pH 10, particle size of 45 μm, particle amount of 1.5 g/L, dye concentration of 455 mg/L, and 60 min. The removal efficiency increased sharply for the first 5 min; after that the removal efficiency reached a steady state at 60 min, with a maximum removal of 88.7%. The kinetic studies for the adsorption of BR18 dye in aqueous solution using hydrochar showed pseudo-second-order kinetics. The Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Freundlich isotherm was the most suitable model because of its high regression coefficient (R²) value. The intraparticle diffusion model was used to determine the adsorption mechanism of BR18 onto Q. coccifera acorn hydrochar. Desorption studies were also carried out using different types of acid and different molarities.

An ultrasonic-assisted synthesis of rice-straw-based porous carbon with high performance symmetric supercapacitors

Biomass porous carbon materials are ideal supercapacitor electrode materials due to their low price, rich source of raw materials and environmental friendliness. In this study, an ultrasonic-assisted method was applied to synthesize the rice-straw-based porous carbon (UPC). The obtained UPC exhibited a two-dimensional structure and high specific surface area. In addition, the electrochemical test results showed that the UPC with a 1 hour ultrasonic treatment and lower activation temperature of 600 °C (UPC-600) demonstrated optimal performance: high specific capacitances of 420 F g⁻¹ at 1.0 A g⁻¹ and 314 F g⁻¹ at a high current of 10 A g⁻¹. Significantly, the symmetric supercapacitors showed a high energy density of 11.1 W h kg⁻¹ and power density of 500 W kg⁻¹. After 10 000 cycles, 99.8% of the specific capacitance was retained at 20 A g⁻¹. These results indicate that UPC-600 is a promising candidate for supercapacitor electrode materials.

Rice-straw-based porous carbon was successfully prepared via an ultrasonic-assisted method to lower activation temperature and for ultra-stable electrode materials of symmetric supercapacitors.

Review of Solvents Based on Biomass for Mitigation of Wax Paraffin in Indonesian Oilfield

This paper presents a review of the expectations and challenges of using biomass in the prevention and slowing of paraffin wax deposition that takes place during the crude oil production process. The inhibition of the deposition process involves the use of solvents from biomass that are generally available around the crude oil production field. The processes used to scale down the precipitation of wax include mixing crude oil with the manufacturer’s solvent composed of toluene and xylene. The goal is to assess solvents sourced from biomass that are capable to slow down the wax deposition process. Wax appearance temperature is an important characteristic to evaluate the possible wax precipitation of a given fluid. Wax precipitation can be reduced by using some chemical additives, often called the pour point depressant. This additive is expected to be produced from local biomass which can compete with solvents currently produced on the market.

Particle size reduction of rice straw enhances methane production under anaerobic digestion

The objective of this study was to investigate the effects of particle size reduction (20, 1, 0.15, and 0.075 mm) on biogas production from rice straw waste through batch anaerobic digestion experiments. To clarify the digestion mechanisms, the microbial community and rice straw properties including fractal dimension, dissolution abilities and the bio-liquefaction degree were determined. Particle size reduction of rice straw improved methane yield from 107 mL g^-1 VS to 197 mL g^-1 VS. The elevated digestion efficiency was attributed to the cellulose degradation (degradation rate from 27% to 93%) rather than hemicellulose or lignin. The comminution pretreatment improved the basic morphology, dissolution abilities and bio-liquefaction degree, which associated with the shifts in the bacterial community and the decreased bacterial diversity. These results suggested that particle size reduction of the rice straw in conjunction with optimized microbial growth could improve the methane yield in anaerobic digestion processes.