Evaluation of foam-glass media in a high-rate filtration process for the removal of particulate matter containing phosphorus in municipal wastewater

Foam-glass as an effective filter media in a high-rate filtration process was evaluated for the removal of particulate matter containing phosphorus in municipal wastewater. The foam-glass with a low sphericity exhibited a higher porosity (60.2%) and a lower apparent specific gravity (0.50 g/cm³) compared with a conventional sand media (35.1% and 1.19 g/cm³). In particular, the high porosity of the foam-glass increased its surface area for capturing particles with coagulation, leading to a significantly decreasing head loss in the filtration bed column, resulting in a significantly longer filtration duration (more than 2 times) and a slightly higher removal of contaminants (approximately 4.8% for a suspended solid and 2% for the total phosphorus). Additionally, while backwashing of the conventional sand media required about 30% of the bed volume, the low specific gravity of the foam-glass media could be expanded to 100% of the volume due to its lower energy demand. Based on these advantages, it is expected that the foam-glass media will have a vital role as an alternative media in high-rate filtration processes.

Adsorption of phosphate from aqueous solution using electrochemically modified biochar calcium-alginate beads: Batch and fixed-bed column performance

Batch and continuous fixed-bed column studies were investigated using electrochemically modified biochar calcium-alginate beads (EMB-CABs) as an adsorbent for the removal of phosphate from aqueous solutions. Batch experiments revealed that the phosphate adsorption behavior of EMB-CABs and its structural characteristics were highly dependent on pH condition. Also, kinetics and equilibrium isotherms studies demonstrated that the experimental data correlated well with the pseudo-second-order and Sips isotherm models, respectively. The effects of different operating parameters such as bed height, initial phosphate concentration, and flow rate were investigated in a continuous fixed-bed column, and the experimental data were fitted to three different breakthrough models, the Adams-Bohart, Thomas, and Yoon-Nelson models. The results suggested that the Yoon-Nelson model showed better agreement with the breakthrough curves than other models. Lastly, the design parameters for a large-scale column were calculated via the scale-up approach using the breakthrough parameters obtained from lab-scale column tests.

Facile synthesis of magnetic biochar/Fe3O4 nanocomposites using electro-magnetization technique and its application on the removal of acid orange 7 from aqueous media

This study introduces a new methodology to synthesize magnetic biochar/Fe3O4 nanocomposites (M-BC) from marine macroalgae using a facile electro-magnetization technique. M-BC was prepared by stainless steel electrode-based electrochemical system, followed by pyrolysis. Physical and chemical analyses revealed that the porosity and magnetic properties were simultaneously improved via the electro-magnetization process, which enabled not only higher adsorption performance, but also easier separation/recovery from aqueous media at post-adsorption stage using a bar magnet. The adsorption equilibrium studies reveal that the Sips model satisfactorily predicts the adsorption capacity, which found to be 190, 297, and 382mgg(-1) at 10, 20, and 30°C, respectively. The overall findings indicate that one-step electro-magnetization technique can be effectively utilized for the fabrication of biochar with concurrent acquisition of porosity and magnetism, which can bring about new directions in the practical use of adsorption process in environment remediation and mitigate crises originating from it.

Fabrication of granular activated carbons derived from spent coffee grounds by entrapment in calcium alginate beads for adsorption of acid orange 7 and methylene blue

Biomass-based granular activated carbon was successfully prepared by entrapping activated carbon powder derived from spent coffee grounds into calcium-alginate beads (SCG-GAC) for the removal of acid orange 7 (AO7) and methylene blue (MB) from aqueous media. The dye adsorption process is highly pH-dependent and essentially independent of ionic effects. The adsorption kinetics was satisfactorily described by the pore diffusion model, which revealed that pore diffusion was the rate-limiting step during the adsorption process. The equilibrium isotherm and isosteric heat of adsorption indicate that SCG-GAC possesses an energetically heterogeneous surface and operates via endothermic process in nature. The maximum adsorption capacities of SCG-GAC for AO7 (pH 3.0) and MB (pH 11.0) adsorption were found to be 665.9 and 986.8mg/g at 30°C, respectively. Lastly, regeneration tests further confirmed that SCG-GAC has promising potential in its reusability, showing removal efficiency of more than 80% even after seven consecutive cycles.

Preparation of modified-biochar from Laminaria japonica: Simultaneous optimization of aluminum electrode-based electro-modification and pyrolysis processes and its application for phosphate removal

The preparation conditions of electro-modification (current density) and pyrolysis (pyrolysis temperature and heating rate) processes were simultaneously optimized using response surface methodology with the quadratic regression model associated with Box-Behnken design. By numerical optimization, the phosphate adsorption capacity of 245.06mg/g was achieved, corresponding to 99.9% of the predicted values under statistically optimized conditions (current density: 38.78mA/cm(2), pyrolysis temperature: 584.1°C, heating rate: 6.91°C/min). By considering R(2) and three error functions values, the experimental results of adsorption kinetics, and the equilibrium isotherms at different temperatures (10-30°C) showed that predictive pseudo-second-order and Sips isotherm models could adequately interpret the phosphate adsorption process for 'statistically optimized electrically modified'-biochar (SOEM-biochar). The maximum phosphate adsorption capacities of SOEM-biochar were found to be 273.9, 345.1, and 460.3mg/g at 10, 20, and 30°C, respectively, which are higher than that of other adsorbents reported in the literature.

Characteristics of biochar derived from marine macroalgae and fabrication of granular biochar by entrapment in calcium-alginate beads for phosphate removal from aqueous solution

In this work, granular biochar, Laminaria japonica-derived biochar (LB)-calcium alginate beads (LB-CAB), was successfully prepared by dropping a mixture of powder biochar and alginate solution into a calcium chloride solution for phosphate adsorption. Among different marine macroalgae derived biochars, LB exhibited the best performance, showing a phosphate removal rate of 97.02%, which was attributed to its high Ca/P and Mg/P ratios. With increasing pyrolysis temperature up to 600°C, the physicochemical properties of LB became suitable for adsorbing phosphate. Experimental results of kinetics and equilibrium isotherms at different temperatures (10-30°C) showed that the phosphate adsorption process is endothermic and is mainly controlled by external mass transfer and the intraparticle diffusion rate. The maximum adsorption capacity was found to be 157.7mgg(-1) at 30°C, as fitted by the Langmuir-Freundlich model, which is higher than capacities of other powder form of biochars.

Influence of pyrolysis temperature on characteristics and phosphate adsorption capability of biochar derived from waste-marine macroalgae (Undaria pinnatifida roots)

The collected roots of Undaria pinnatifida, the main waste in farming sites, accounting for 40-60% of annual production, was pyrolyzed under temperature ranging from 200 to 800°C to evaluate the influence of pyrolysis temperature on biochar properties and phosphate adsorption capacity. It was confirmed that an increase in the pyrolysis temperature led to a decrease of the yield of biochar, while ash content remained almost due to carbonization followed by mineralization. Elemental analysis results indicated an increase in aromaticity and decreased polarity at a high pyrolysis temperature. When the pyrolysis temperature was increased up to 400°C, the phosphate adsorption capacity was enhanced, while a further increase in the pyrolysis temperature lowered the adsorption capacity due to blocked pores in the biochar during pyrolysis. Finally, a pot experiment revealed that biochar derived from waste-marine macroalgae is a potent and eco-friendly alternative material for fertilizer after phosphate adsorption.

Phosphate adsorption ability of biochar/Mg-Al assembled nanocomposites prepared by aluminum-electrode based electro-assisted modification method with MgCl₂ as electrolyte

In this work, the textural properties and phosphate adsorption capability of modified-biochar containing Mg-Al assembled nanocomposites prepared by an effective electro-assisted modification method with MgCl2 as an electrolyte have been determined. Structure and chemical analyses of the modified-biochar showed that nano-sized stonelike or flowerlike Mg-Al assembled composites, MgO, spinel MgAl2O4, AlOOH, and Al2O3, were densely grown and uniformly dispersed on the biochar surface. The adsorption isotherm and kinetics data suggested that the biochar/Mg-Al assembled nanocomposites have an energetically heterogeneous surface and that phosphate adsorption could be controlled by multiple processes. The maximum phosphate adsorption capacity was as high as 887 mg g(-1), as fitted by the Langmuir-Freundlich model, and is the highest value ever reported. It was concluded that this novel electro-assisted modification is a very attractive method and the biochar/Mg-Al assembled nanocomposites provide an excellent adsorbent that can effectively remove phosphate from aqueous solutions.

A novel approach for preparation of modified-biochar derived from marine macroalgae: Dual purpose electro-modification for improvement of surface area and metal impregnation

In the present study, an aluminum electrode-based electrochemical process was newly adopted as a modification method for fabricating physically and chemically modified biochar derived from marine macroalgae. Specifically, a current density of 93.96 mA cm(-2) was applied for 5 min at pH 3.0. Subsequently, the mixture was stirred continuously for 30 min without electric field, and the dried sample was then pyrolyzed at 450 °C under a N2 environment for 2 h. SEM-EDS and XRD analyses clearly indicated that nano-sized aluminum crystals (beohemite, AlOOH) were uniformly present on the EM-biochar surface. Adsorption equilibrium tests showed that the phosphate adsorption onto EM-biochar agreed well with the Langmuir-Freundlich adsorption isotherm model, with a maximum adsorption capacity of 31.28 mg-P g(-1). These findings suggest that this novel and simple electro-modification method is a reasonable and effective option for simultaneously upgrading both the surface area and chemical properties of biochar.