This study assesses the application of iron (III) trimesic (Fe-BTC) as a coagulant-flocculant to remove lignin from pulp and paper (P&P) wastewater. In this research, Fe-BTC was characterized by X-ray diffraction (XRD), while the functional groups of Fe-BTC and lignin were analyzed by Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) determined the surface morphology of the material. The influential parameters affecting lignin removal included the initial lignin concentration, the quantity of Fe-BTC, and the pH which were investigated using a single batch mixing system. The experimental and optimum operational conditions were determined using Box-Behnken design (BBD). Fe-BTC dosage plays a major role in efficiently removing lignin, while the pH and initial lignin concentration had no significant effect. Greater than 80% removal efficiency could be achieved with a Fe-BTC dosage as low as 2 g/L. The proposed mechanism of lignin aggregation was that Fe molecules were released from unsaturated sites of Fe-BTC and then formed new bonds with O in the methoxy lignin group. The interaction between Fe-BTC and lignin was π-π stacking (benzene ring), which explains the formation of F-O bonds in the lignin sludge. ABSTRAK Kajian ini menilai penggunaan besi (III) trimesik (Fe-BTC) sebagai bahan penggumpal untuk menyingkirkan lignin daripada air sisa pulpa dan kertas (P&P). Dalam kajian ini, Fe-BTC dicirikan oleh pembelauan sinar-x (XRD) manakala kumpulan fungsian Fe-BTC dan lignin dianalisis melalui spektroskopi transformasi Fourier inframerah (FT-IR). MikroskopElektron Imbasan (SEM) menentukan morfologi permukaan untuk bahan. Parameter penting yang menyebabkan penyingkiran lignin adalah termasuk kepekatan pemula lignin, kuantiti Fe-BTC dan pH yang dikaji menggunakan sistem campuran kelompok tunggal. Syarat uji kaji dan pengoperasian optimum telah ditentukan dengan menggunakan reka bentuk Box-Behnken (BBD). Dos Fe-BTC memainkan peranan penting dalam menyingkirkan lignin dengan cekap, manakala pH dan kepekatan pemula lignin tidak menunjukkan kesan yang ketara. Lebih daripada 80% kecekapan penyingkiran boleh dicapai dengan dos Fe-BTC serendah 2 g/L. Mekanisme cadangan daripada pengagregatan lignin adalah bahawa Fe molekul dibebaskan dari unsatured tapak Fe-BTC dan kemudian membentuk ikatan baharu dengan O dalam kumpulan lignin metoksi. Interaksi antara Fe-BTC dan lignin ialah susunan π-π (gelang benzena) yang menjelaskan pembentukan ikatan F-O dalam enap-cemar lignin.Kata kunci: Fe-BTC; lignin; MOFs; pulpa dan kertas; rangka kerja logam-organik; reka bentuk Box-Behnken

This study aimed to optimize the condition of silica-supported nanoscale zero valent iron (NZVI/SiO 2) synthesis by colloidal impregnation method. Box-Behnken design (BBD) was used as a tool to create and analyze the 17 synthesized conditions of NZVI/SiO 2 samples. The independent variables included ethanol concentration (0-100 vol%), amount of silica (0.025-0.125 g) and agitation speed (100-400 rpm). In addition, analysis of variance (ANOVA) for a response surface quadratic model was used to approximate statistical relationship of independent variables. The reducing performance of the synthesized NZVI/SiO 2 was examined through removal of Cr(VI) contaminated in water. The optimum of NZVI/SiO 2 synthesis was validated with 100 vol% of ethanol concentration, 0.075 g of silica amount, and 100 rpm of agitation speed. The materials were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and nitrogen adsorption/desorption which showed the existence of NZVI phase, composition, and morphology. The Cr(VI) removal efficiency of the NZVI/SiO 2 was tested further at the solution pH 4, 7 and 10 in comparison with that by pristine NZVI and silica-unsupported NZVI (NZVI + SiO 2). Among the three materials, NZVI/SiO 2 presented the highest Cr(VI) removal, especially at pH 7 and 10 with 98 and 94.41%, within 60 min. This was due to the adsorption of Cr(OH) 3 and Fe(OH) 3 precipitates over SiO 2 resulting in availibilty of NZVI/SiO 2 's active sites. The proposed mechanism of Cr(VI) removal by NZVI/SiO 2 was also described.

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Vinasse, a sugar-ethanol residue, is used as a substrate for biogas production. The characteristics of the vinasse wastewater used were 216,000 mg-COD/L, pH 4.1, and 68.42 mg/L volatile solids. The sludge/wastewater ratio was controlled at about 1.5−2.0, by weight. Biogas production enhancement was studied in relation to two parameters – Citadel BioCat + , a commercial biocatalyst containing a large microorganism population as the methanogenic bacteria source (5 and 10 g), and reaction temparature (30 and 37 °C). Biogas production kinetics were evaluated. The presence of the biocatalyst enhanced biogas production significantly, as well as reducing the time required for anaerobic digestion. The first-order kinetic model described the biodegradation process. The best results were found using 10 g of biocatalyst at 37 °C – i.e., the optimum results based on biogas production potential (A), the highest biogas production rate (U), the minimum biogas production time (λ), and kinetic organic biodegradability constants (k) of 102.71 mL/g-COD, 11.17 mL/g-COD/d, 0.95 day, and 0.0533 day − 1, respectively. COD removal efficiency was up to 60%.