Performance characterization and application of composite adsorbent LiCl@ACFF for moisture harvesting

Freshwater scarcity is a global threat to modern era of human society. Sorption-based atmospheric water harvesting (AWH) is prospective to provide fresh water for remote water-stressed areas lacking in water and electricity. Adsorbent material plays a vital role in such AWH systems. Here, we report a solid adsorbent synthesized by impregnating hygroscopic salt lithium chloride (LiCl) into solidified activated carbon fiber felt (ACFF modified by silica sol). Composite samples immersed with different mass concentrations of silica sol are prepared and characterized for dynamic water uptake, equilibrium water uptake, textural and thermal properties. AS5Li30 (ACFF + 5 wt% silica gel + 30 wt% LiCl) exhibits an efficient water uptake of 2.1 g/g at 25 °C and 70% relative humidity (RH). The material further demonstrates a heat storage capacity of 5456 kJ/kg. Its low regeneration temperature (< 80 °C) and good cycle stability make it feasible to be used in practical water production applications, driven by solar energy and other low-grade energy. Estimation results show that water harvesting unit can produce 1.41 gH2O/gAS5Li30 under 25 °C and 75% RH.

Low-Cost Single Chamber MFC Integrated With Novel Lignin-Based Carbon Fiber Felt Bioanode for Treatment of Recalcitrant Azo Dye

A flow through anaerobic microbial fuel cell (MFC) was designed and optimized for efficient treatment of recalcitrant textile wastewater. The membrane-less MFC was first time fabricated with a unique combination of electrodes, a novel bioanode of synthesized lignin-based electrospun carbon fiber supporting a biofilm of Geobacter sulfurreducens for acetate oxidation and an air-breathing cathode, consisting of a pyrolyzed macrocycle catalyst mixture on carbon bonded by polytetrafluoroethylene (PTFE). The effects of different organic loadings of acetate along with Acid Orange (AO5), operation time and ionic strength of auxiliary salts (conductivity enhancers) were investigated and responses in terms of polarization and degradation were studied. In addition, the decomposition of the organic species and the degradation of AO5 along with its metabolites and degraded products (2-aminobenzenesulfonic acid) were determined by chemical oxygen demand (COD) analysis, UV-Vis spectrophotometry and high-performance liquid chromatography (UV-HPLC) techniques. SEM and TEM images were also used to find out the biocompatibility of the microbes on lignin-based electrospun carbon felt anode and the morphology of the cathode. Reduction and breakage of the azo bond of AO5 occurs presumably as a side reaction, resulting in the formation of 2-aminobenzenesulfonic acid and unidentified aromatic amines. Maximum current density of anode 0.59 Am−2 and power density of 0.12 Wm−2 were obtained under optimized conditions. As a result, decolouration of AO5 and chemical oxygen demand (COD) removal efficiency was 81 and 58%, respectively. These results revealed that the low-cost MFC assembly can offer significant potential for anaerobic decolouration of recalcitrant textile wastewater.

Performance of Combined Electrocoagulation-Advanced Electrochemical Oxidation Used for Oil Field Produced Water Treatment

Considerable amounts of produced water (PW) are usually accompanied with theproduction of oil. This study proposed a combination of electrocoagulation (EC) - electro-Fenton (EF) process for oxidation organic compounds in PW to reduce the chemical oxygendemand (COD) to below regulation limits. The PW used in this study was collected fromoilfield in the Midland Oil Company. Pretreatment of the PW was conducted using batch ECtechnique with aluminum electrodes to eliminate the suspended and dissolved solids and toreduce the COD and treatment cost. Optimization of EC process revealed that optimum currentdensity, pH, and reaction time were 7.83 mA/cm2, 7.24, 20.40 minutes respectively. Underthese conditions the COD removal percentage was 73.97% starting from initial COD of 1730mg/l.Batch and continuous electro-Fenton processes were investigated using dimensionallystable anode Ti-RuO2/IrO2 and activated carbon fiber felt (ACFF) cathode. The effect ofcrucial process variables on COD removal efficiency was investigated using response surfacemethodology. A second order polynomial model equations were constructed and the resultswas analyzed by the analysis of variance (ANOVA). It was concluded that a combination ofelectrocoagulation followed by electro-Fenton process is effective for treating oilfieldproduced water and further improvement can be achieved by photo assisting the process. Atotal COR removal efficiency of 98% was achieved.