Adsorption of copper from water using TiO2-modified activated carbon derived from orange peels and date seeds: Response surface methodology optimization.

This study evaluated the application and efficiency of modified activated carbon in the removal of copper (Cu) from synthetic aquatic samples. The surface of activated carbon derived from orange peel (AC-OP) and date seeds (AC-DS) have been modified by Titanium dioxide nanoparticles (TiO2 NPs) (1:10 wt% mixing ratio) and used in a series of experiments designed by Response Surface Methodology (RSM) incorporating Central Composite Design (CCD). The Brunauer-Emmett-Teller (BET) test demonstrated that the modification has increased the surface area of AC-OP from 2.40 to 6.06 m2 g-1 and AC-DS from 51.10 to 81.37 m2 g-1. Effects of pH (1-7), ion initial concentration (10-60 mg L-1), adsorbent dose (0.5-8 g L-1), and contact time (0.4-6 h) have been investigated. The results showed that the optimum conditions for TiO2-modified AC-OP (OP-TiO2) are pH 5, initial concentration of 24.6 mg L-1, adsorbent dose of 4.9 g L-1, and contact time of 3.6 h. The optimum conditions for TiO2-modified AC-DS (DS-TiO2) are pH 6.4, initial concentration of 21.2 mg L-1, adsorbent dose of 5 g L-1, and contact time of 3.0 h. The modified quadratic models represented the results well with regression coefficients of 0.91 and 0.99 for OP-TiO2 and DS-TiO2, respectively. The maximum Cu removal for OP-TiO2 and DS-TiO2 were 99.90 % and 97.40 %, and the maximum adsorption capacity was found to be 13.34 and 13.96 mg g-1, respectively. Kinetic data have been fitted to pseudo first-order, pseudo second-order, intra-particle diffusion, and Elovich models. The pseudo second-order showed a better fit to the experimental data (R2 > 98 %). This study demonstrates the successful development of modified activated carbon derived from orange peels and date seeds, modified by TiO2 nanoparticles, for efficient adsorption of copper ions from water. The findings contribute to understanding the adsorption mechanism and provide valuable insights for designing environmentally friendly adsorbents.

Olive stone as an eco-friendly bio-adsorbent for elimination of methylene blue dye from industrial wastewater.

Adsorbents synthesized by activation and nanoparticle surface modifications are expensive and might pose health and ecological risks. Therefore, the interest in raw waste biomass materials as adsorbents is growing. In batch studies, an inexpensive and effective adsorbent is developed from raw olive stone (OS) to remove methylene blue (MB) from an aqueous solution. The OS adsorbent is characterized using scanning electron microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Brunauer-Emmett-Teller (BET) surface area. Four isotherms are used to fit equilibrium adsorption data, and four kinetic models are used to simulate kinetic adsorption behavior. The obtained BET surface area is 0.9 m2 g-1, and the SEM analysis reveals significant pores in the OS sample that might facilitate the uptake of heavy compounds. The Langmuir and Temkin isotherm models best represent the adsorbtion of MB on the OS, with a maximum monolayer adsorption capacity of 44.5 mg g-1. The best dye color removal efficiency by the OS is 93.65% from an aqueous solution of 20 ppm at the OS doses of 0.2 g for 90 min contact time. The OS adsorbent serves in five successive adsorption cycles after a simple filtration-washing-drying process, maintaining MB removal efficiency of 91, 85, 80, and 78% in cycles 2, 3, 4, and 5, respectively. The pseudo second-order model is the best model to represent the adsorption process dynamics. Indeed, the pseudo second-order and the Elovich models are the most appropriate kinetic models, according to the correlation coefficient (R2) values (1.0 and 0.935, respectively) derived from the four kinetic models. The parameters of the surface adsorption are also predicted based on the mass transfer models of intra-particle diffusion and Bangham and Burt. According to the thermodynamic analysis, dye adsorption by the OS is endothermic and spontaneous. As a result, the OS material offers an efficient adsorbent for MB removal from wastewater that is less expensive, more ecologically friendly, and economically viable.

Recovery of fuel from real waste oily sludge via a new eco-friendly surfactant material used in a digital baffle batch extraction unit.

This study focused on developing a new cocktail extraction agent (CEA) composed of solvent and a new surfactant material (SM) for enhancing the efficiency of fuel recovery from real waste oil sludge (WSO). The effects of different solvents (e.g. methyl ethyl ketone (MEK), naphtha, petrol and kerosene), SMs (Dowfax and sodium thiosulfate), extraction time (10-20 min), extraction temperatures (20-60 °C) and CEA/sludge ratios (1-4) on the extraction performance were investigated. SMs and DBBE design enhanced the extraction efficiency by increasing the dispersion of solvent in WSO and enhancing the mixing and mass transfer rates. Results proved that Dowfax was the best SM for oil recovery under various conditions. The best CEA (e.g. MEK and Dowfax) provides the maximum fuel recovery rate of 97% at a period of 20 min, temperature of 60 °C and 4:1 CEA/sludge ratio. The produced fuel was analysed and fed to the distillation process to produce diesel oil. The characteristics of diesel oil were measured, and findings showed that it needs treatment processes prior its use as a finished fuel.

Strategies To Improve the Performance of Hydrogen Storage Systems by Liquefaction Methods: A Comprehensive Review.

The main challenges of liquid hydrogen (H2) storage as one of the most promising techniques for large-scale transport and long-term storage include its high specific energy consumption (SEC), low exergy efficiency, high total expenses, and boil-off gas losses. This article reviews different approaches to improving H2 liquefaction methods, including the implementation of absorption cooling cycles (ACCs), ejector cooling units, liquid nitrogen/liquid natural gas (LNG)/liquid air cold energy recovery, cascade liquefaction processes, mixed refrigerant systems, integration with other structures, optimization algorithms, combined with renewable energy sources, and the pinch strategy. This review discusses the economic, safety, and environmental aspects of various improvement techniques for H2 liquefaction systems in more detail. Standards and codes for H2 liquefaction technologies are presented, and the current status and future potentials of H2 liquefaction processes are investigated. The cost-efficient H2 liquefaction systems are those with higher production rates (>100 tonne/day), higher efficiency (>40%), lower SEC (<6 kWh/kgLH2), and lower investment costs (1-2 $/kgLH2). Increasing the stages in the conversion of ortho- to para-H2 lowers the SEC and increases the investment costs. Moreover, using low-temperature waste heat from various industries and renewable energy in the ACC for precooling is significantly more efficient than electricity generation in power generation cycles to be utilized in H2 liquefaction cycles. In addition, the substitution of LNG cold recovery for the precooling cycle is associated with the lower SEC and cost compared to its combination with the precooling cycle.

Anaerobic Digestion of Pig-Manure Solids at Low Temperatures: Start-Up Strategies and Effects of Mode of Operation, Adapted Inoculum, and Bedding Material.

The objective of this study was to obtain start-up strategies for the operation of a dry anaerobic digestion (DAD) system treating pig-manure (PM) solids at low-temperatures, and evaluate the effects of operation mode, adapted inoculum, and bedding material on the performance. A DAD system coupled with an inoculum system (two-stage DAD) was operated at 20 ± 1 °C to digest PM solids (Total Solids, TS: 27%) with wheat straw or woodchips as bedding materials (TS substrate-mixture: 45%) using a liquid inoculum. Static DAD was also operated in parallel for comparison purposes. Overall, the percolation-recirculation mode of operation was superior to the static mode; the former had more than a 3-fold increase in specific methane yield in cycle 3. Using the adapted inoculum in cycle-2 improved methane yield by 7% and 26% for cycles 1 and 3, respectively, under the percolation-recirculation mode of operation. In addition, the digestate resulting from the digestion of woodchips + PM solids had better physical characteristics than wheat straw + PM solids. Thus, anaerobic digestion of pig-manure solids at low-temperatures with appropriate start-up strategies, inoculum, and bedding material is a promising technology for transforming PM solids into biogas and using its digestate as biofertilizer.

A start-up of psychrophilic anaerobic sequence batch reactor digesting a 35 % total solids feed of dairy manure and wheat straw.

Zero liquid discharge is currently an objective in livestock manure management to minimize water pollution. This paper reports the start-up phase of a novel psychrophilic (20 °C) dry anaerobic digestion of dairy manure with bedding fed at 35 % total solids and an organic loading rate of 3.0 g total chemical oxygen demand kg(-1) inoculum day(-1) in anaerobic sequence batch reactors. The specific methane (CH4) yield ranged from 165.4 ± 9.8 to 213.9 ± 13.6 NL CH4 kg(-1) volatile solids (VS) with an overall average of 188 ± 17 NL CH4 kg(-1) VS during 11 successive start-up cycles (231 days) and a maximum CH4 production rate of 10.2 ± 0.6 NL CH4 kg(-1) VS day(-1). The inoculum-to-substrate (VS-based) ratio ranged from 4.06 to 4.47. Although methanogenesis proceeded fairly well the hydrolysis seemed to be the rate limiting step. It is possible start up psychrophilic dry anaerobic digestion of cow feces and wheat straw at feed TS of 35 % within 7-10 successive cycles (147-210 days).

High rate psychrophilic anaerobic digestion of undiluted dairy cow feces.

Novel high rate psychrophilic (20°C) anaerobic digestion (PAD) of undiluted cow feces (11.5-13.5% total solids) was demonstrated using sequence batch reactor in long-term operation with successive cycles of 21days treatment cycle length (TCL). At organic loading rates (OLR) 9.0, 10.0, 11.0 and 12.0g TCOD kg(-1) inoculum d(-1) average specific methane yield (SMY) was 154.0±11.7, 152.1±12.2, 126.0±2.8 and 116.0±6.1NL CH4 per kg of VS fed, respectively. Volatile solids removal averaged around 31.7±3.3%, 32.2±1.0%, 27.9±2.2% and 23.4±0.5%, respectively. Substrate-to-inoculum ratio (SIR; wet-mass basis) ranged between 1.17±0.06 and 1.43±0.05. Concentration of volatile fatty acids in the bioreactors during the TCL indicated that hydrolysis was the rate limiting reaction. High rate PAD of undiluted cow feces is possible at OLR (g TCOD kg(-1) inoculum d(-1)) 9.0 and 10.0 with a TCL of 21days; however, OLR of 11.0 and 12.0 are also possible but require longer TCL to maintain the SMY.

High rate psychrophilic anaerobic digestion of high solids (35%) dairy manure in sequence batch reactor.

Zero liquid discharge is increasingly adopted as an objective for waste treatment process. The objective of this study was to increase the feed total solids (TS) and the organic loading rate (OLR) fed to a novel psychrophilic (20°C) dry anaerobic digestion (PDAD). Duplicate laboratory-scale bioreactors were fed cow feces and wheat straw (35% TS in feed) at OLR of 6.0 g TCOD kg(-1) inoculum d(-1) during long-term operation (147 days consisting of 7 successive cycles). An overall average specific methane yield (SMY) of 151.8±7.9 N L CH4 kg(-1) VS fed with an averaged volatile solids removal of 42.4±4.3% were obtained at a volatile solids-based inoculum-to-substrate ratio (ISR) of 2.13±0.2. The operation was stable as indicated by biogas and VFAs profiles and the results were reproducible in successive cycles; a maximum SMY of 163.3±5.7 N L CH4 kg(-1) VS fed was obtained. Hydrolysis was the reaction limiting step. High rate PDAD of 35% TS dairy manure is possible in sequential batch reactor within 21 days treatment cycle length.

Dry anaerobic digestion of high solids content dairy manure at high organic loading rates in psychrophilic sequence batch reactor.

Cow manure with bedding is renewable organic biomass available around the year on dairy farms. Developing efficient and cost-effective psychrophilic dry anaerobic digestion (PDAD) processes could contribute to solving farm-related environmental, energy, and manure management problems in cold-climate regions. This study was to increase the organic loading rate (OLR), fed to a novel psychrophilic (20 °C) dry anaerobic digestion of 27% total solid dairy manure (cow feces and wheat straw) in sequence batch reactor (PDAD-SBR), by 133 to 160%. The PDAD-SBR process operated at treatment cycle length of 21 days and OLR of 7.0 and 8.0 g total chemical oxygen demand (TCOD) kg(-1) inoculum day(-1) (5.2 ± 0.1 and 5.8 ± 0.0 g volatile solids (VS) kg(-1) inoculum day(-1)) for four successive cycles (84 days) produced average specific methane yields (SMYs) of 147.1 ± 17.2 and 143.2 ± 11.7 normalized liters (NL) CH4 kg(-1) VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.45 at OLR of 8.0 g TCOD kg(-1) inoculum day(-1). Hydrolysis was the limiting step reaction. The VS removal averaged around 57.4 ± 0.5 and 60.5 ± 5.7% at OLR 7.0 and 8.0 g TCOD kg(-1) inoculum day(-1), respectively.

Impact of organic loading rate on the performance of psychrophilic dry anaerobic digestion of dairy manure and wheat straw: long-term operation.

Development of efficient processes for valorising animal wastes would be a major advancement in cold-climate regions. This paper reports the results of long term (315 days experiment) of novel psychrophilic (20°C) dry anaerobic digestion (PDAD) of cow feces and wheat straw in laboratory scale sequence batch reactor operated at increasing organic loading rate. The PDAD process fed with a mixture of feces and straw (TS of 27%) over a treatment cycle length of 21 days at organic loading rate (OLR) 4.0, 5.0 and 6.0 g TCOD kg(-1) inoculum d(-1) (of 2.9 ± 0.1, 3.7 ± 0.1, and 4.4 ± 0.1g VS kg(-1) inoculum d(-1), respectively) resulted in average specific methane yield (SMY) of 187.3 ± 18.1, 163.6 ± 39.5, 150.8 ± 32.9 N L CH4 kg(-1)VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.4 at OLR of 6.0 g TCOD kg(-1) inoculum d(-1). Hydrolysis was the limiting step reaction.

Effect of Corn Dried Distiller Grains with Solubles (DDGS) in Dairy Cow Diets on Manure Bioenergy Production Potential.

The main objective of this study was to obtain scientifically sound data on the bioenergy potential of dairy manures from cows fed different levels of corn dried distillers grains with solubles (DDGS). Three diets differing in corn DDGS content were formulated: 0% corn DDGS (DDGS0; control diet), 10% corn DDGS (DDGS10) and 30% corn DDGS (DDGS30). Bioenergy production was determined in psychrophilic (25 ± 1 °C) sequencing batch reactors (SBRs) fed 3 g COD L(-1)·day(-1) during a two-week feeding period followed by a two-week react period. Compared to the control diet, adding DDGS10 and DDGS30 to the dairy cow diet increased the daily amount of fat excreted in slurry by 29% and 70%, respectively. The addition of DDGS30 increased the cows' daily production of fresh feces and slurry by 15% and 11%, respectively. Furthermore, the incorporation of DDGS30 in the diet increased the daily amounts of dry matter (DM), volatile solids (VS), neutral detergent fiber (NDF), acid detergent fiber (ADF) and hemicellulose by 18%, 18%, 30%, 15% and 53%, respectively, compared to the control diet. While the addition of DDGS did not significantly affect the specific CH4 production per kg VS compared to the control diet, DDGS30 increased the per cow daily CH4 production by 14% compared to the control diet.

Potential of Biological Processes to Eliminate Antibiotics in Livestock Manure: An Overview.

Degrading antibiotics discharged in the livestock manure in a well-controlled bioprocess contributes to a more sustainable and environment-friendly livestock breeding. Although most antibiotics remain stable during manure storage, anaerobic digestion can degrade and remove them to various extents depending on the concentration and class of antibiotic, bioreactor operating conditions, type of feedstock and inoculum sources. Generally, antibiotics are degraded during composting > anaerobic digestion > manure storage > soil. Manure matrix variation influences extraction, quantification, and degradation of antibiotics, but it has not been well investigated. Fractioning of manure-laden antibiotics into liquid and solid phases and its effects on their anaerobic degradation and the contribution of abiotic (physical and chemical) versus biotic degradation mechanisms need to be quantified for various manures, antibiotics types, reactor designs and temperature of operations. More research is required to determine the kinetics of antibiotics' metabolites degradation during anaerobic digestion. Further investigations are required to assess the degradation of antibiotics during psychrophilic anaerobic digestion.

Psychrophilic anaerobic digestion of lignocellulosic biomass: a characterization study.

Psychrophilic (20°C) specific methane (CH4) yield from cellulose (C), xylan (X), cellulose/xylan mixture (CX), cow feces (CF), and wheat straw (WS) achieved (Nl CH4 kg(-1)VS) of 338.5 ± 14.3 (C), 310.5 ± 3.4 (X), 305.5 ± 29.6 (CX mixture), and 235.3 ± 22.7 (WS) during 56 days, and 237.6 ± 17.7 (CF) during 70 days. These yields corresponded to COD recovery of 73.3 ± 3.1% (C)=69.1 ± 0.76% (X)=67.3 ± 5.8% (CX mixture)>52.9 ± 2.6% (CF)>46.5 ± 2.7% (WS). Cellulose-fed culture had a lower and statistically different initial CH4 production rate from those calculated for cultures fed X, CX mixture, CF and WS. It seemed that the presence of hemicellulose in complex substrate such as wheat straw and cow feces supported the higher initial CH4 rate compared to cellulose. Biomethanation of the pure and complex lignocellulosic substrates tested is feasible at psychrophilic conditions given that a well-adapted inoculum is used; however, hydrolysis was the rate limiting step.

Utilizing settling tests to design a conventional upflow settling tank modified with inclined plates.

This paper examines the relationships between the turbidity removal efficiency (TRE), the surface overflow rate (SOR), and the detention time (D(t)) in settling column and jar tests, as well as the performance of a conventional upflow settling tank modified with inclined plates in the upper zone. The experimental results showed that the SOR obtained from the flocculent settling column test can be increased by 30% and the corresponding D(t) can be decreased by 75% with a variation in TRE of less than 7%. The TRE of flocculent settling in the jar test coincided with the performance of the modified upflow settling tank, while the results of the settling column test were slightly different. For plain settling, the SOR obtained from jar and settling column tests should be divided by 3 and 2, respectively, before possible use in the design of the modified upflow settling tank. Two empirical models with 1.0% error in the TRE predictions were developed to facilitate the design of the modified upflow settling tank.