Sustainable wastewater purification with crab shell-derived biochar: Advanced machine learning modeling & experimental analysis

Detoxifying ecologically persistent dyes is vital for environmental and human well-being. Herein, crabshell waste is transformed into porous carbon (CB900) through pyrolysis, achieving a remarkable removal rate of 90.5% (CR-RR) and adsorption capacity (∼256.36 mg g-1, qCR). Employing XGBoost modeling, with a robust R2 ∼0.996, proved its superiority over others in predicting CR adsorption. PSO-XGB optimization led to an optimal configuration: 0.051 g adsorbent, 460.56 mg L-1 CR concentration, pH 3.16, and a 94.01 min contact time, resulting in 68.39% CR-RR and 822.15 mg g-1 qCR, simultaneously; sensitivity analysis unveiled the pivotal role of pH and adsorbent dose. CB900 exhibited physical, spontaneous, endothermic following both Langmuir and Freundlich isotherms. Remarkably, CB900 effectively eliminated various contaminants, including chromium and sulfasalazine antibiotic. Pilot-scale CB900 production cost via pyrolysis was $8.5/kg, a fraction of commercial powdered activated carbon, underscoring its economic viability and potential as a sustainable solution for the elimination of toxic contaminants from aqueous environments.

Mesoporous silica synthesized from natural local kaolin as an effective adsorbent for removing of Acid Red 337 and its application in the treatment of real industrial textile effluent

This paper presents a synthesis of mesoporous silica (MS) from natural clay as a silica source using Pluronic L35 (EO11PO16EO11) as a structure-directing agent. The prepared material was characterized by XRD, X-ray fluorescence, thermogravimetric analysis, SEM, TEM, and N2 adsorption-desorption analyses. Then, mesoporous material was used for the removal of Acid Red 337 (AR337) from aqueous solution, and the treatment of real textile effluent. The effect of pH, contact time, weight of adsorbent, and initial concentration was studied in batch adsorption. The synthesized mesoporous material showed good discoloration efficiency with a 62% percentage. Experiment with real textile wastewater showed that 39%, 40%, and 31.5% of the color, TOC, and chemical oxygen demand respectively were eliminated by using 1 g of MS per liter of wastewater.

Treatment of zinc plating wastewater by combination of electrocoagulation and ultrafiltration process

In this study treatment of zinc plating wastewater by combination of electrocoagulation (EC) and ultrafiltration (UF) processes was investigated. The effect of operating parameters such as wastewater pH, flow rate and membrane pore size on zinc removal was investigated to optimize the EC-UF process. The results showed that zinc removal was pH dependent and optimum pH was 9.0. The zinc removal over 99% was achieved by the combined EC-UF process with both 50 and 100 kDa membranes at pH 9.0 and current density of 5 mA cm^-2. Suspended solids and oil-grease were also removed completely by the combined EC-UF process. The EC-UF process proved to be a promising technology for the treatment and recycling of zinc plating wastewater.

A comparative study of ozonation, iron coated zeolite catalyzed ozonation and granular activated carbon catalyzed ozonation of humic acid

This study compares ozonation (O₃), iron coated zeolite catalyzed ozonation (ICZ-O₃) and granular activated carbon catalyzed ozonation (GAC-O₃) for removal of humic acid from an aqueous solution. The results were evaluated by the removal of DOC that specifies organic matter, UV₂₅₄ absorbance, SUVA (Specific Ultraviolet Absorbance at 254 nm) and absorbance at 436 nm. When ozonation was used alone, DOC removal was 21.4% at an ozone concentration of 10 mg/L, pH 6.50 and oxidation time of 60 min. The results showed that the use of ICZ or GAC as a catalyst increased the decomposition of humic acid compared to ozonation alone. DOC removal efficiencies were 62% and 48.1% at pH 6.5, at a catalyst loading of 0.75 g/L, and oxidation time of 60 min for ICZ and GAC, respectively. The oxidation experiments were also carried out using <100 kDa and <50 kDa molecular size fractions of humic acid in the presence of ICZ or GAC. Catalytic ozonation also yielded better DOC and UV₂₅₄ reduction in both <50 kDa and <100 kDa fractions of HA compared to ozonation.

Adsorption of basic dyes from aqueous solution onto pumice powder

The adsorption of methylene blue and crystal violet on pumice powder samples of varying compositions was investigated using a batch adsorption technique. The effects of various experimental parameters, such as adsorbent dosage, initial dye concentration, and contact time, were also investigated. The extent of dye removal increased with decreased initial concentration of the dye and also increased with increased contact time and amount of adsorbent used. Adsorption data were modeled using the Freundlich adsorption isotherm. The adsorption kinetic of methylene blue and crystal violet could be described by the pseudo-second-order reaction model.

Sorption of phenol and 4-chlorophenol onto pumice treated with cationic surfactant

In this study the sorption of phenol and 4-chlorophenol on pumice modified with the cationic surfactants hexadecyltrimethyl ammonium bromide (HDTMA) and benzyldimethyl tetradecylammonium chloride (BDTDA) was investigated. Experimental studies indicate that HDTMA-pumice and BDTDA-pumice have the capability to remove phenol and 4-chlorophenol from aqueous solution. The influence of initial concentration and adsorbent dosage was studied. The adsorption of phenol and 4-chlorophenol increased with increasing initial concentration and decreased with increasing amount of adsorbent used. The Freundlich adsorption isotherm was found to describe well the equilibrium adsorption data. The parameters of the Freundlich model have been determined using the adsorption data.

Photocatalytic degradation of phenol

In this study photocatalytic degradation of phenol in the presence of UV irradiated TiO2 catalyst and H2O2 was investigated. Effects of TiO2 and H2O2 concentrations and pH on photocatalytic degradation were examined. The rate constants for photocatalytic degradation were evaluated as a function of TiO2 and H2O2 concentrations and pH of the solution. It was found that photodegradation is an effective method for the removal of phenol and disappearance of phenol obeyed first order kinetics. The amount of CO2 produced during photocatalytic degradation was corresponding to the complete mineralization. Photodegradation can be an alternative method for the treatment of phenol containing wastewaters.