Box-Behnken design (BBD) was employed to study an optimal treatment method of synthetic lignin wastewater effluent from pulp and paper wastewater treatment plants using iron (III) trimesate (Fe-BTC) as an alternative coagulant aid. Fe-BTC was prepared by hydrothermal technique using ferric chloride hexahydrate (FeCl3·6H2O) combined with 1,3,5-benzenetricarboxylic acid (trimesic acid, H3BTC) in deionized water and ethanol. X-ray diffractometry and Fourier transform infrared spectroscopy were used to characterize the property of Fe-BTC. Three quadratic models of the four factors including Fe-BTC dosage, pH, initial lignin concentration, and slow mixing time were defined with lignin removal efficiency as a response. Treatment efficiency of lignin removal was 50-80% for experimental data and 60-80% for predicted values. Optimal condition was 1 g/L of Fe-BTC dosage, pH 4, and 50 ppm of initial lignin concentration without slow mixing giving 58.34% lignin removal efficiency. The pH of treated samples was below 3 after all processes. Results showed that Fe-BTC enhanced separation of lignin by coagulation-flocculation. Adsorption-charge neutralization is the main mechanism of this process at acidic pH. Fe-BTC separated the wastewater into three layers with Fe-BTC powder at the bottom, lignin sludge in the middle, and clear supernatant at the top. Lignin sludge can be reused and recycled for use in other applications.
Arsenite (As(III)) has threatened human life for ages. It is a necessity to remove As(III) from the contaminated water before general use. With the improvement of adsorption, higher As(III) removal can be achieved. This study aimed to develop zeolite/cerium oxide coat-on activated alumina ball adsorbent (CeZ-ball) with the aid of PVA binder and apply it to a fixed-bed continuous flow column for As(III) adsorption. The coating percentage of CeZ-ball was studied. Cerium ions leaching from CeZ-ball were monitored throughout the 2,880-min-column run to confirm the stability of CeZ attached to an activated alumina ball. Surface area, pH point of zero charge, and structural property of CeZ-ball were characterized. An average CeZ coating of 83.3% and rare leaching of cerium proved the coating method. The models proposed by Yoon-Nelson provided the most satisfactory fit with the breakthrough curve (r2 = 0.985, MPSD = 2.547, and q0 = 3.481 mg·g–1) under experimental conditions of the flow rate of 5 mL·min–1, As(III) influent concentration of 1 mg·L–1, and CeZ-ball weight of 40 g. The half-time of breakthrough (τ) was 1,228.739 min. The effects of the key parameters, including initial adsorbent weight, initial flow rate, and initial As(III) concentration, were investigated for the performance of As(III) adsorption. Simulated from the Yoon-Nelson model, the τ increased as well as the adsorbent weight but decreased as the flow rate increased, thus impacting the As(III) concentration. With the optimal condition, the fixed-bed continuous column with CeZ-ball could be used in As(III) removal from contaminated water.
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