Study on optimal adsorption conditions of norfloxacin in water based on response surface methodology

The waste pomelo peel was pyrolyzed at 400 °C to prepare biochar and used as adsorbent to remove norfloxacin (NOR) from simulated wastewater. The adsorption conditions of norfloxacin by biochar were optimized by response surface methodology (RSM). On the basis of single-factor experiment, the adsorption conditions of biochar dosage, solution pH and reaction temperature were optimized by Box-Behnken Design (BBD), and the quadratic polynomial regression model of response value Y1 (NOR removal efficiency) and Y2 (NOR adsorption capacity) were obtained respectively. The results show that the two models are reasonable and reliable. The influence of single factor was as follows: solution pH > biochar dosage > reaction temperature. The interaction between biochar dosage and solution pH was very significant. The optimal adsorption conditions after optimization were as follows: biochar dosage = 0.5 g/L, solution pH = 3, and reaction temperature = 45 °C. The Y1 and Y2 obtained in the verification experiment were 75.68% and 3.0272 mg/g, respectively, which were only 2.38% and 0.0242 mg/g different from the theoretical predicted values of the model. Therefore, the theoretical model constructed by response surface methodology can be used to optimize the adsorption conditions of norfloxacin in water.

Degradation of Azo Dyes with Different Functional Groups in Simulated Wastewater by Electrocoagulation

Increasing attention has been paid to the widespread contamination of azo dyes in water bodies globally. These chemicals can present high toxicity, possibly causing severe irritation of the respiratory tract and even carcinogenic effects. The present study focuses on the periodically reverse electrocoagulation (PREC) treatment of two typical azo dyes with different functional groups, involving methyl orange (MO) and alizarin yellow (AY), using Fe-Fe electrodes. Based upon the comparative analysis of three main parameters, including current intensity, pH, and electrolyte, the optimal color removal rates for MO and AY could be achieved at a rate of up to 98.7% and 98.6%, respectively, when the current intensity is set to 0.6 A, the pH is set at 6.0, and the electrolyte is selected as NaCl. An accurate predicted method of response surface methodology (RSM) was established to optimize the PREC process involving the three parameters above. The reaction time was the main influence for both azo dyes, while the condition of PREC treatment for AY simulated wastewater was time-saving and energy conserving. According to the further UV–Vis spectrophotometry analysis throughout the procedure of the PREC process, the removal efficiency for AY was better than that of MO, potentially because hydroxyl groups might donate electrons to iron flocs or electrolyze out hydroxyl free radicals. The present study revealed that the functional groups might pose a vital influence on the removal efficiencies of the PREC treatment for those two azo dyes.

Phosphorus Co-Existing in Water: A New Mechanism to Boost Boron Removal by Calcined Oyster Shell Powder

The removal of boron (B) from water by co-precipitation with hydroxyapatite (HAP) has been extensively studied due to its low cost, ease of use and high efficiency. However, there is no explicit mechanism to express how resolved B was trapped by HAP. Thus, in this work, the process of removing B from water was studied using a low-cost calcium (Ca) precipitation agent derived from used waste oyster shells. The results showed that the removal rate of B in the simulated wastewater by calcined oyster shell (COS) in the presence of phosphorus (P) is up to more than 90%, as opposed to virtually no removal without phosphate. For B removal, the treated water needs to be an alkaline solution with a high pH above 12, where B is removed as [CaB(OH)4]+ but is not molecular. Finally, the synergistic mechanism of co-precipitation between HAP and dissolved B, occlusion co-precipitation, was explained in detail. The proposed method discovered the relationship between Ca, P and B, and was aimed at removing B without secondary pollution through co-precipitation.

Removing of Cadmium Ions and Reactive red Dye from Simulated Wastewater Using Eggshell as an Eco-Friendly Material

The research aims to use eggshells (ES) as civilian residues in the process of removing cadmium ions and reactive red dye according to international standards limits. Synthetic solutions were prepared for cadmium ions and reactive red dye using 0.2 g non-calcined and calcined ES at various temperatures (25, 250, 500, 750, and 1000 ℃) as an adsorbent. The result showed the removal of cadmium ion was (60, 100%) for non-calcined and calcined ES, respectively, with the initial concentration of cd2+ (10 ppm). The removal of reactive red dye was (18.5, 98%) using non-calcined and calcined ES, respectively, at a concentration of red dye (50 ppm). The best removal time was 90 min. XRD and FTIR spectroscopy were performed and the results were identical to the main components of ES and changed with temperature increasing due to dissolution of calcium carbonate (CaCO3).

Predesign cost estimation of a potential wastewater treatment plant for Jordan petroleum refinery-Electrocoagulation

The aim of this paper is to investigate whether simulated Jordan refinery wastewater can be treated through electrocoagulation (EC) to conform to the most stringent Jordanian norms for reusing this wastewater for irrigation of cut flowers and to perform cost analysis for a treatment plant whose core are the EC reactors. The method used for estimating the fixed (capital) costs of the treatment plant is taken from literature and is based on a study estimate (factored estimate) that depends on the knowledge of major items of equipment. Most of the operating costs are estimated based on percentages which are also taken from literature. The best percentage removal of COD, BOD, TSS, fat, oil& grease (FOG), bicarbonate (HCO3 −), and phenol from simulated Jordan refinery wastewater so that it conforms to Jordanian norms were 84.4%, 82.1%, 27.3%, at least 98.8%, 94.9%, at least 96.7%, respectively, at a current of 10 A, treatment time of 5 minutes, Al/SS electrodes, and inter-electrode distance 10 mm. Overall treatment costs for the simulated wastewater was 10.75 $/m3 (27 $/kg CODremoved). It is concluded that simulated Jordan refinery wastewater cannot be treated so that it conforms to the most stringent norms for using the treated wastewater for cut flowers irrigation but could be treated enough to conform to the Jordanian norms for using the treated water for irrigation of cooked vegetables, parks, and playgrounds. Moreover, EC is a suitable technology for the treatment of Jordanian recalcitrant refinery wastewater and the cost for its treatment is affordable.

Pilot-Scale Microsand-Ballasted Flocculation of Wastewater: Turbidity Removal, Parameters Optimization, and Mechanism Analysis

The flocs formed during microsand-ballasted flocculation (MBF) have attracted much attention. However, few studies have reported on comprehensive process parameters of MBF and its mechanism is still not well understood. Jar test and pilot-scale continuous experiments were here conducted on two kinds of simulated wastewater, labeled S1 (21.6-25.9 NTU) and S2 (96-105 NTU). Results revealed the hydraulic retention time ratio in the coagulation cell, injection & maturation cell, lamella settler of pilot-scale MBF equipment was 1: 3: 7.3. The optimum poly aluminum chloride doses for Samples S1 and S2 were 0.875 g/L and 1.0 g/L. Besides, the optimum size of microsand was 49-106 µm and the optimum dose was 1.0 g/L. Under aforementioned conditions, the effluent turbidity of S1 was below 0.47 NTU, lower than the Chinese drinking water standard; that of S2 was below 1.7 NTU, meeting the Chinese recycled water standard. Turbidity removal ranged from 98.0% to 98.8% for S1 and 98.5% to 99.5% for S2 when microsand was added. Therefore, microsand addition enhances MBF performance, where microsand serves as an initial core particle. Some microsand core particles bond together to form a dense core structure of micro-flocs by the adsorption bridging of inorganic polymeric flocculant. Moreover, the size of the largest micro-flocs may be controllable as long as the effective energy dissipation ɛ0 is adjusted appropriately through specific stirring speeds. This work provides comprehensive pilot-scale process parameters for using MBF to effectively treat wastewater and offers a clearer explanation of the formation mechanism of microsand-ballasted flocs.

Research on the Adsorption Effects of Biomass by Microstructural Characterization and Intelligent Numerical Computation Method

In this paper, sodium sulfide solution as a simulation of sulfur-containing wastewater, using orange peel as adsorbent, through the change of the absorbance of simulated wastewater to analyze the orange peel adsorbent on the treatment effect of simulated wastewater, to explore its optimal experimental conditions. The experimental results show that the adsorbent has a certain adsorption effect on the sulfur compounds in the sulfur-containing wastewater. With the change of the pH value of the adsorption environment, the adsorption rate has changed. The addition of different chemical modifiers in the water will affect the adsorption and effect of orange peel.