This review highlights the recent technologies of H2S removal from wastewater in the petroleum refinery. H2S is a harmful, putrid, and hazardous gaseous compound. The main processes such as physicochemical, chemical, biological, and electrochemical methods were compared and discussed in detail. The effects of various parameters and adsorbent characteristics were highlighted and correlated with the adsorption capacities. Surface functional groups and porosity surface area play a crucial role in the process of single-phase and composite adsorbents. Composite materials impregnated with some metals showed high removal efficiencies. It was found that the adsorption process is the most relevant way for H2S removal due to its high removal efficiency, low cost, eco-friendly, and operational simplicity. This study serves as a useful guideline for those who are interested in H2S removal.

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Background: White Piper nigrum is an important commodity crop containing a number of essential bioactive components with nutritional and medicinal properties when sufficiently extracted. Microwave refluxation is therefore a novel technique employed in the extraction of bioactive components from natural products of plant origin. This method doubled as classical and traditional solvent extraction techniques with reduced extraction time, higher selectivity, low solvent consumption, and higher extraction rate. Methods: The Taguchi L 9 -orthogonal design was employed to determine a combination of extraction factors that jointly optimized the extraction yield. The use of this para metric design was due to its ability to mitigate inherent noise factor with minimal experimental trials. Results: The optimal extraction condition was attained at 90 min of irradiation time, 300 W of microwave power, 0.105 mm of particle size, and 10 ml/g of molar ratio. Under this condition, the corresponding optimum extraction yield of 4.278 (v/w)% was obtained. Moreover, the percentage contribution of each extraction factor on the response settings resulted in the decreasing order: irradiation time > molar ratio > power level > particle size. Phytochemical screening was condcuted on the oleoresin extracts and a total number of 26 bioactive compounds were identified. Also, the Fourier Transform Infrared Analysis (FTIR) and the Scanning Eectron Microscopy (SEM) confirmed the presence of seven presence of seven functional groups with an observable structural transformation.

a b s t r ac tPalm kernel shell is an abundant agricultural by-product in Malaysia, which is mainly used for producing activated carbon (AC) via the process called physicochemical activation. The applicability of AC derived from palm kernel shell (ACPKS) was investigated for the removal of dissolved H 2 S from wastewater. ACPKS was characterized by energy-dispersive X-ray, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area and scanning electron microscope. The batch mode was utilized for studying adsorption capacity. The effects of various parameters were evaluated and these parameters were then optimized. Parameters such as initial concentration (500 mg/L), dose (100 mg/L), pH (7), agitation speed (150 rpm) and contact time (14 h) for removing dissociated H 2 S were optimized. Equilibrium data for H 2 S adsorption on ACPKS were fitted using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The experimental data were comparable to the predictions of Langmuir equation, where the maximum monolayer adsorption capacity of 524.2 mg/g was found. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were employed for simulating the experimental data for the adsorption kinetics. Among these models, the pseudo-first-order model was the best fitting model based on the correlation coefficients (R 2 ) and normalized standard deviation (sum of squared error). The current study shows that ACPKS is the promising adsorbent for removing H 2 S from wastewater and other aqueous solutions.

The studies of adsorption equilibrium isotherm and kinetics of hydrogen sulfide-water systems on calcite-based adsorbents prepared from eggshell are undertaken. The effects of operating variables such as contact time and initial concentration on the adsorption capacity of hydrogen sulfide are investigated. The modified eggshells are characterized by using different analytical approaches such as Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR). The batch mode adsorption process is performed at optimum removal conditions: dosage of 1 g/L, pH level of pH 6, agitation speed of 150 rpm and contact time of 14h for adsorbing hydrogen sulfide with an initial concentration of 100-500 mg/L. In the current study, the Langmuir, Freundlich, Temkin, and Dubinin models are used to predict the adsorption isotherms. Our equilibrium data for hydrogen sulfide adsorption agrees well with those of the Langmuir equation. The maximum monolayer adsorption capacity is 150.07 mg/g. Moreover, the kinetics of H2S adsorption by using the modified calcite of eggshell follows a pseudo-second-order model. From the current work, we have found that the calcite eggshell is a suitable adsorbent for H2S embeded inside the waste water. Most importantly, chicken eggshell is a waste and vastly available; hence, it could serve as a practical mean for H2S adsorption.

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Due to the upsurge of awareness of the depletion of fossil fuel feedstock and environmental issues, biodiesel has become a more attractive choice. Biodiesel's productivity is deemed a fruitful and significant research field since its relevance obtains from the increased oil prices and environmental benefits. This paper presents a study of Alfa waste cooking oil used to produce biodiesel oil via the transesterification process. The investigation includes various variables such as transesterification time, catalyst ratio, temperature, and biodiesel yield. Two catalysts (NaOH and KOH) have been utilized in this study. The engine test was carried out at constant load with increasing speed to compare different fuels' performance relative to mineral diesel. The produced biodiesel was categorized according to ASTM D6751. The highest conversion and yield of biodiesel in the transesterification method were scrutinized using the KOH catalyst compared to the NaOH catalyst. The maximum conversion and yield of biodiesel are 97.76 and 94.4%, respectively, with optimum operating conditions of 60 o C reaction temperature, 3 hours reaction time, and KOH catalyst at 4% weight. Consequently, the engine test outcomes revealed similar biodiesels trends compared to diesel in terms of engine brake power and brake specific fuel consumption with increasing engine speed.