• Energy Research

This study aimed to investigate the physicochemical properties of sugar industry and ethanol distillery wastewater and the treatment of the blended wastewater through a two-stage anaerobic reactor. For this treatment, different initial chemical oxygen demand (COD) concentrations (5-20 g/L) and hydraulic retention times (HRTs) (2-10 days) were applied. The sugar industry effluent characteristics obtained in terms of organic matter (mg/L) were as follows: 5 days biochemical oxygen demand (BOD5): 654.5-1,968; COD: 1,100-2,148.9; total solids (TS): 2,467-4,012 mg/L; and pH: 6.93-8.43. The ethanol distillery spent wash strengths obtained were: BOD5: 27,600-42,921 mg/L; COD: 126,000-167,534 mg/L; TS: 140,160-170,000 mg/L; and pH: 3.9-4.2. Maximum COD removal of 65% was obtained at optimum condition (initial COD concentration of 10 g/L and HRT of 10 days), and maximum color removal of 79% was recorded under similar treatment conditions. Hence, the performance of the two-stage anaerobic reactor for simultaneous removal of COD and color from high-strength blended wastewater is promising for scaling up in order to mitigate environmental problems of untreated effluent discharge.

In this study, a heterogeneous basic catalyst was synthesized from a catalyst composite material (CCM) of coffee husk ash and char mixture (A/C) impregnated with KNO3 and employed to transesterify crude waste frying oil (WFO). The effect of CCM calcination temperature (CCMCT) (500-700 °C) on the catalyst physicochemical properties was investigated. A differential scanning calorimeter was used to examine potential phase changes during the calcination of A/C and CCM. The catalysts from each CCMCT were characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller surface area analyzer, scanning electron microscopy (SEM), SEM with energy-dispersive X-ray diffractometer, colorimeter, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometer. The methoxy functional group FTIR peak integral value and the dynamic viscosity of the biodiesel synthesized by each catalyst were used to determine the qualitative WFO conversion. Furthermore, the quantitative WFO conversion was determined using nuclear magnetic resonance (1H NMR) analysis. Crystallinity, elemental composition, basicity, and morphology of catalysts were highly dependent on the CCMCT. Without transesterification condition optimization (reaction temperature of 45 ± 2.5 °C, catalyst loading of 3 wt %, methanol to oil molar ratio of 12:1, and reaction time of 1 h), a higher catalytic performance (72.04% WFO conversion) was reached using a catalyst from the CCMCT of 600 °C. When using a coffee husk ash catalyst without KNO3 impregnation (C-00-600), the WFO conversion was only 52.92%. When comparing the C-25-600 and C-00-600 catalysts, it was observed that KNO3 impregnation had a substantial impact on the catalyst crystallinity, basicity, and morphology.

In this study, a KNO3-loaded coffee husk (CH) ash catalyst was synthesized to produce waste frying oil methyl ester (WFOME) from crude waste frying oil (WFO). Taguchi method optimization was performed to identify the best set of reaction temperature, time, catalyst loading and methanol to WFO molar ratio for maximum WFOME yield. A catalyst composite material (CCM) which is a mixture of CH char and KNO3 (0–65 wt%) was calcined to obtain the catalyst. The KNO3 loading and CCM calcination time effects on the catalyst performance and physicochemical properties were examined. The combustion behavior of the CH and CCMs was investigated using thermal analysis techniques. Utilizing FTIR, XRD, BET, SEM, and pH measurements, the catalyst characterization was carried out. For analytical sample sizes (during thermal analysis) with high KNO3 loading, the thermal reactivity was higher. However, for larger sample sizes (during catalyst synthesis) higher KNO3 loading decreased the CCM global thermal reactivity due to an oxygen permeation resisting ash deposition on the top surface. Thus, KNO3 tuned the catalyst’s physicochemical properties as a function of its loading (optimum 45 wt%) by affecting the combustion characteristics of the CCMs and basic site concentration. The optimum WFOME yield was 97.99 wt% at a reaction temperature of 65 °C, a reaction time of 1.13 h, a catalyst loading of 5.42 wt%, and a methanol to WFO molar ratio of 13.55:1. The WFOME yield was dropped by 46.93 wt% in three consecutive catalyst reuse tests because of active components leaching.