Regeneration potential of activated petroleum coke for application in oil sands process-affected water

Cost effective regeneration of spent adsorbent is crucial for large scale application of adsorption as a viable separation process. While adsorption studies are abundant in literature, systematic and comprehensive regeneration studies are seldom reported in open literature. A proprietary activated carbon from petroleum coke was used for the removal of model naphthenic acids (NAs) and organic compounds from oil sands process-affected water (OSPW). A systematic and comprehensive study was conducted to regenerate the adsorbents. Methanol with aqueous NaOH (pH adjusted to around 12) was applied to regenerate the spent commercially available granular activated carbon (GAC) and activated petroleum-coke (APC). Optimization of solvent volume, solvent pH, regeneration time, and agitation speed was evaluated in preliminary batch experiments. Higher adsorption capacity and regeneration efficiency were achieved for APC due to higher mesoporous surface area during the treatment of two model compounds (2-naphthoic acid and diphenylacetic acid) and NAs rich OSPW than that of the GAC. Thereafter, the optimum regeneration scheme was applied in continuous column operations for recycling the adsorbents. Although, the bed adsorption capacity decreased dramatically after first cycle, the capacity could be stabilized after 2 repeated adsorption-desorption cycles. The regenerating solvent (methanol) was recovered effectively (maximum 90% recovery ratio) using vacuum distillation. Moreover, Na-salts of NA were recovered, which have some commercial applications. A desorption kinetics model was also developed which would be useful for future scaling up of the process

Effect of Pretreatment of Resin Acids on Anaerobic Digestibility of Pulp and Paper Mill\u27s Primary Sludge

Pulp and paper (P&P) mills’ wastewater contain high concentrations of resin acids (10–10,000 mg/L) which are toxic to aquatic organisms. In mill’s primary and waste activated sludge treatments reduced concentrations of resin acids in effluent; however, most of the resin acids are ultimately ended up in sludge after primary and secondary clarification due to their extreme hydrophobic nature (log Kow 6.0). Nevertheless, adsorbed resin acids on the surfaces of anaerobes and substrates affect anaerobic digestion (AD) process negatively. The objective of the present work was to determine the effect of pretreatment of thermomechanical pulping mill’s primary sludge (TMP-PS) on AD. The performance of ozone and ferrate pretreatment of TMP-PS on AD was evaluated at their optimum pH around 11.0 and 7.0, respectively. Pretreatment of TMP-PS using 0.150 mg dosages /mg tCOD of ferrate and ozone increased sCOD by around 28.35% and 22.88%, respectively besides reduction of 23.63%, and 37.07% resin acids, respectively. AD showed negligible biodegradation of resin acids by anaerobic consortia. Pretreatment with ferrate and ozone increased the methane yield by maximum of 60.15% and 49.62%, respectively. Compared to ozonation, 11–13% more methane was generated in ferrate pretreated digesters. However, according to cost analysis, ozonation of TMP-PS is economically more feasible than ferrate pretreatment

Development of treatment train based on green technologies for removal and recovery of naphthenic acids from oil-sand process affected wastewater

Each day large volumes of oil sands process-affected water (OSPW) are being produced during the extraction of bitumen in oil sands industry in northern Alberta. OSPW contains different polyaromatic hydrocarbons (PAHs), bitumen, as well as naphthenic acids (NAs), which not only are the major source of toxicity in OSPW, but also create operational problems such as corrosion of the equipment during bitumen recovery process. A recent figure indicates that about 720 billion liters of OSPW that were produced during the extraction of bitumen from Canadian oil sands industry have been stored in tailing ponds that cover approximately 170 km2. Water treatment and management strategies are urgently needed for OSPW recycling in order to reduce the withdrawal of fresh water from the Athabasca River and to permit the safe release of treated OSPW to the receiving environment by removing these compounds. OSPW is highly saline water with myriad of organic and inorganic constituents, including metals, anions, organic compounds, and suspended particles. Among all the different treatment methods, adsorption has gained significant attention due to its efficiency and fast removal rates. Recent studies on petroleum coke (PC), a relatively inexpensive and abundant feedstock, used as an adsorbent after activation, have brought renewed attention to the use of adsorption processes for OSPW treatment. The coagulation/flocculation (CF) process is widely used as a pre-treatment to other processes including adsorption. Besides adsorption, desorption of exhausted adsorbents is crucial to naphthenic acids recovery due to various industrial applications. The unique properties of the metallic soaps of naphthenic acids account for the major uses of the acid. The salts of naphthenic acids (alkali naphthenates) are applied as both emulsifying and demulsifying agents. The metallic naphthenates have also found industrial application in the fields of preservatives and driers. Copper and zinc naphthenates are effective insecticides and fungicides, and solutions of these salts in petroleum solvents are available commercially. Please click Additional Files below to see the full abstract

Micropollutants in Wastewater: Fate and Removal Processes

The occurrence of micropollutants (MPs) in various streams of municipal wastewater treatment plants (WWTPs), and their fate and removal processes are discussed. The fate of MPs in WWTPs largely depends on adsorption on suspended particulates, primary and secondary sludge and dissolved organic carbon, and removal occurs due to coagulation-flocculation, and biodegradation. The log Kow (>2.5) and pKa are the dominant properties of the MPs, and the concentration, organic fraction, and surface charge of suspended particulates dictate the extent of adsorption of MPs. Most of the conventional WWTPs do not remove complex MPs by biodegradation or biotransformation effectively (kbio ≤0.0042 L/gss/h), and the removal varies widely for different compounds, as well as for the same substance, due to operational conditions such as aerobic, anaerobic, anoxic, sludge retention time (SRT), pH, redox potential, and temperature. Membrane bioreactor performs better for moderately biodegradable compounds due to the diverse nature of microorganisms as well as greater adaptability due to longer SRT. Ozone and UV-based advanced oxidation processes, membrane filtration can be used for tertiary treatment due to their high rate as well as easy implementation. Various partition coefficients and rate constants values for different MPs are also provided for design and application

A Novel Biosorbent, Water-Hyacinth, Uptaking Methylene Blue from Aqueous Solution: Kinetics and Equilibrium Studies

The adsorption of MB dye from aqueous solution onto HCl acid treated water-hyacinth (H-WH) was investigated by carried out batch sorption experiments. The effect of process parameters such as pH, adsorbent dosage, concentrations and contact time, and ionic strength were studied. Adsorption of MB onto H-WH was found highly pH dependent and ionic strength shows negative impact on MB removal. To predict the biosorption isotherms and to determine the characteristic parameters for process design, Langmuir, Freundlich, Temkin, and Halsey isotherms models were utilized to equilibrium data. The adsorption kinetics was tested for pseudo-first-order (PFO), pseudo-second-order (PSO), intraparticle diffusion (IPD), and Bangham’s kinetic models. The Langmuir isotherm model showed the goodness-of-fit among the tested models for equilibrium adsorption of MB over H-WH and indicated the maximum adsorption capacity as 63.30 mg/g. Higher coefficient of determination (R2>0.99) and better agreement between the qe (experimental) and qe (calculated) values predicted that PSO kinetic model showed the goodness-of-fit for kinetic data along with rate constant 1.66×10-3, 4.42×10-3, and 3.57×10-3 mg·g-1min⁡-1/2⁡, respectively, for the studied concentration range. At the initial stage of adsorption, the overall rate of dye uptake was found to be dominated by external mass transfer, and afterwards, it is controlled by IPD mechanism

Assessment of Organic Acid-Rich Bio-Sap to Generate Electricity

The study has focused on electricity generation from organic acid-rich bio-substrate like star fruit (Averrhoa carambola). The sap of star fruit was selected as an electrolyte due to the presence of significant amounts of organic acids such as citric acid and ascorbic acid. To preserve the sap, 2% phenol by volume was used to reduce the growth of microorganisms, and the addition of phenol did not affect the initial pH. It was observed that due to an increase in the electrode surface area, reaction rate and current generation had been amplified. Internal resistance also decreased rapidly because of the large electrode surface area. Furthermore, internal resistance was the significant barrier in electricity generation, which was also successfully controlled by the baffle flow agitation system. Moreover, the baffle flow agitation system reduces the formation of dead zones and increases the total dissolved solids inside the electrochemical cell compartments during operation

Generation of Electricity from Whey: An Electrochemical Process

This study is concentrated on the electricity generation from whey over and done with a fabricated electrochemical cell. Whey (milk serum) is one of the prominent sources of bio-electrolyte because of containing abundant amount of branched-chain amino acids. It is one of the non-useable by-products in the sweetmeat company and also harmful for our environmental pollution in case of open dumping. We choose whey because of its low pH content about 3.1-3.3. Moreover, the utilization of this kind of waste material can be important raw materials for power generation. Two categories of preservation techniques have been revealed by thermal treatment and adding 2% phenol by volume. It was observed that phenol treated whey was free form microbial attack for longer time compared to that of thermal treatment. The measurement of voltage and power density is important to estimate the efficiency and competency of the system. In agitation assisted bio-electrochemical reactor, voltage and power density were increased with the increase of electrode surface area. Maximum 17.35 volt was obtained from 6.5 litres of whey through an agitation assisted electrochemical reactor. In addition, commercial alloy electrode shows satisfactory results on power generation and reducing internal resistance compares with the experimental pure metal electrode. This technology has implication on the recovery of the power crisis in rural and remote areas where the national electricity supply is inaccessible. This approach is also convenient for portable use of electricity in household purposes