Application of Chemically Modified and UnmodifiedWaste Biological Sorbents in Treatment ofWastewater

Protein wastes (feathers, goat hair) and cellulosic wastes (corn cob, coconut husks) were collected and washed with detergent solution, thoroughly rinsed and sun dried for 2 days before drying in an oven, and then ground. One-half of ground material was carbonized at a maximum temperature of 500◦C after mixing with H2SO4. The carbonized parts were pulverized; both carbonized and uncarbonized sorbents were sieved into two particle sizes of 325 and 625 μm using mechanical sieve. Sorbents of a given particle size were packed into glass column.Then, textile wastewater that had its physicochemical parameters previously determined was eluted into each glass column and a contact time of 60 and 120 mins was allowed before analysis. Results showed 48.15–99.98 percentage reduction of NO3 −, EC, Cl−, BOD, COD, DO, TSS, and TDS, 34.67–99.93 percentage reduction of NO3−, EC, Cl−, BOD, COD, DO, TSS, and TDS, 52.83–97.95 percentage reduction of Pb2+, Ni2+, Cr3+ and Mn2+ and 34.59–94.87 percentage reduction of Pb2+, Ni2+, Cr3+ and Mn2+. Carbonization, small particle, size and longer contact time enhanced the sorption capabilities of the sorbents. These show that protein and cellulosic wastes can be used to detoxify wastewater.


Introduction
Wastewater may be purely domestic or may contain some industrial wastewater as well [1].Residential wastewater is a combination of excreta, flush water, and all types of wastewater generated from household.It is more commonly known as sewage and much diluted.There are two types of domestic sewage: black water or wastewater from toilets and gray water, which is wastewater from all sources except toilets [2].Industrial wastewater comes from commercial activities (shops, restaurants, fast food shops, hospitals, etc.), industries (e.g., chemical industries, pharmaceutical companies, textile manufacturing, etc.), agriculture (e.g., Slurry), and so forth.Wastewaters from dyeing operations are characterized by color caused by both organic and inorganic compounds [3].
The organic compounds are more problematic in industrial effluent than inorganic materials [4,5] because, apart from the color, it imparts on the wastewater, biodegradation of organic material in the dye depleting the dissolved oxygen of the water thereby stressing aquatic microbes [6].Traditional wastewater treatment technologies have shown to be ineffective for handling synthetic dyes because of the chemical stability of these pollutants [7].
There is no single or economically attractive method of treatment of textile wastewater [8], although notable achievements were made in the use of biotechnological approaches to solving the problem recently as reviewed by dos Santos et al. [9].In addition to biological treatment, many physical and chemical treatment methods have been employed for dye removal from wastewaters such as coagulation, flocculation, filtration, oxidation or reduction, complex formation, or neutralization [10].New adsorption/oxidation, adsorption/reduction, and many combined processes were reviewed by Qu [11], while radiationinduced degradation process for treatment of wastewater was reviewed by Wojnarovites and Takacs [12].Solid sorbents have been employed in adsorption techniques to remove certain classes of chemical pollutants from waters; activated carbon is the most successfully used, but the high operating costs and problems with regeneration of the spent activated carbon discourage its large-scale application.Therefore, a number of nonconventional sorbents have been tried for the treatment of wastewaters, in this class are various industrial wastes, agrowaste, or natural materials available in large quantity at low cost and are classified as alternative sorbents for the removal of inorganic and organic pollutants from wastewaters [13][14][15][16].In this present study, the aim is to determine the efficacy of chemically modified and unmodified biological (proteinous and cellulosic) waste sorbents in treatment of textile wastewater; also the effect of particle sizes, carbonization (activation), and contact time will be established.

Collection of Sorbents and Preparation.
Cellulosic waste sorbents (corn cob and coconut-husk (coir)) were procured from a local market around Awka, while protein waste sorbents (goat hair and chicken feathers) were sourced from Awka main abattoir.They were thoroughly washed with soap solution, sun dried for two days before drying in an oven at 105 • C for 2 hours, and then ground.One-half of each ground material was carbonized at a temperature of 300 • C for 30 mins, cooled and activated with H 2 SO 4 , and further heated at a temperature of 500 • C for complete carbonization.The carbonized materials were again pulverized.Both materials were sieved into two particle sizes of 325 µm and 625 µm using mechanical sieve.

Wastewater Collection and Analysis.
Textile wastewater was collected from general cotton mills Onitsha.Physicochemical parameters of the wastewater were analyzed before and after contacting with the adsorbents for each contact time and particle size.
Nitrate was determined according to American Public Health method [17], and chemical oxygen demand (COD) was determined by the dichromate method [18].Biological oxygen demand (BOD) and dissolved oxygen (DO) were determined electrochemically [19].
The chloride content was determined by colorimetric method, while total suspended solid (TSS) and total dissolved solid (TDS) were determined by their respective standard methods [19].A standard pH meter was used to determine the pH, and a digital conductometer (consort K120, Belgium) was used to determine electrical conductivity (EC).Heavy metals (Pb, Mn, Ni, and Cr) were determined at their respective wavelengths (281.5, 278, 231, and 358) nm after digestion using clean filtrates of the samples by means of atomic absorption spectrophotometry 205 A.
2.5 g of each sorbent (both carbonized and uncarbonized and each particle size) were separately packed in glass adsorption column with inner diameter 11 m, bed height 270 mm; the wastewater was eluted into it and allowed a contact time of 60 and 120 minutes.The wastewater was collected after 60 and 120 mins, respectively, and all the previous parameters were again determined to ascertain the percentage absorption after each batch.Results are shown in Tables 1-4.
From Table 4, using carbonized sorbents at 60 mins contact time, 325 µm corn cob showed highest percentage absorption of Pb 2+ and Ni 2+ , while 325 µm coconut husk showed highest percentage absorption of Mn 2+ and Cr 3+ from the wastewater.Using 625 µm, coconut husk absorbed highest percentage Pb 2+ and Cr 3+ , while 625 µm corn cob showed highest percentage absorption of Mn 2+ and Ni 2+ .Using the uncarbonized at the same contact time, 325 µm coconut husk had more percentage affinity for Pb 2+ and Cr 3+ while 325 µm corn cob did so for Mn 2+ and Ni 2+ .Using 625 µm, corn cob sorbed more percentage of Pb 2+ , Ni 2+ , and Cr 3+ , while 625 µm coconut husk sorbed highest percentage of Mn 2+ .

Discussion
Solid wastes can be advantageously used as alternative sorbents because of their low cost and local availability.Adsorption of a basic dye-methylene blue and an acidic dye-eosin on wood dust of different particle size at varying speed has been studied by monitoring color reduction [20].Sawdust and related waste materials from timber industry that are readily available and are inexpensive sorbents have been used to remove unwanted chemical substances from waters including dyes, oils, toxic salt, and heavy metals [9,21].Several cellulose-based waste materials which originate from agroindustry can be used as sorbents for synthetic dyes, such include banana and orange peels [22], olive pomace [23], palm kernel fibre [24], cotton fibre [25], several others have also been used to sequestrate metals from aqueous solution [26,27].Since most applied materials are cellulosic, adequate attention has not been given to studies on sorption capacity of protein waste.This study has proved that protein-based waste sorbent are more efficacious in removal of pollutants from wastewater (Tables 1 and 3).This assertion is in comparison with cellulosic sorbents when placed side by side at the same particle size, activation (carbonization), and contact time, although cellulosic sorbents under study are highly efficient pollutant absorbent/adsorbent (Tables 2 and 4).A critical analysis of the results (Tables 1-4) shows high percentage reduction in the concentrations of parameters analyzed.The differences The variations observed in the study may be as a result of adsorptiondesorption phenomenon occurring at dynamic equilibrium as adsorption may be governed by physical interaction [29].It may also be due to agitation from wind (atmospheric phenomenon) or structural vibration.It can also be due to the fact that absorption/adsorption is nonstoichiometry and there may be inhomogeneity in the shapes, particle sizes, surface area, pore size, morphology of the sorbents, and specific retention volume for each target compounds by the sorbents.Although only textile wastewater was used in this work [30], the method can be applied to all types of waters as present result compared well with previous work in which activated and unactivated powders of rice and groundnut husk were used to remediate brewery and beverage wastewater [31].NO 3 − , BOD, COD and DO were analyzed to establish the presence of chromophores (group of atoms responsible for dye color as well as electron withdrawing or donating substituents that modify or intensify the color of chromophores called auxochromes).The most important chromophores are azo (-N=N-), carbonyl (-C=O), methine (-CH), nitro (-NO 2 ), and quinoid while auxochromes are amine (-NH 2 ), sulfonate (-SO 3 H), carboxyl (-COOH), and hydroxyl (-OH) [9].Electrical conductivities were drastically reduced by all the sorbents at all particle size, contact time, and activation following the normal trends already observed.There was also noticeable color reduction though not of interest in the present study.The decrease in the pH comparing with the base wastewater values shows that the active sites on the sorbents were protonated and the sorbents become positively charged; this may cause steric hinderance which may be responsible for the less percentage absorption of Cr 3+ than other metal ions.This is despite the fact that Cr 3+ is of lower density than other metal ions in the study, the densities are Cr 3+ (7.19), Ni 2+ (8.90), Mn 2+ (7.42), and pb 2+ (11.34) [32].It also depends on the lone pair of electrons available on the sorbents active sites and pore size, as pore size is inversely proportional to surface area [33].Since absorption/adsorption of pollutants by sorbents in this study cannot be attributed to any chemical interaction between the sorbents and chemical pollutants, it can be merely be attributed to weak physical adhesive forces such as van der waal, London forces as well as by mere physical entanglement/occlusion.From this work, excluding minor variation, it is established that protein sorbents have high percentage absorption capacity than cellulose but the later tend to be more abundant and therefore cost effective.In both, carbonization (activation), small particle size (large surface area), and longer contact time have overriding effect on the efficiency of biological waste sorbent in remediating wastewater; this observation is supported by other works [25,27].It is suggested that if three (3) adsorption glass columns are to be connected in series and the sorbents in each column is allowed a contact time of 120 mins with the wastewater before the same water is allowed entering into the next (2nd) column, and allowed another 120 mins contact time before -99.29), COD (38.21-78.93),BOD (41.05-81.48),DO (36.67-81.33),Cl − (50.20-83.61),TSS (94.76-97.57),TDS (97.61-99.91),and EC (87.50-89.58),while the range of percentage absorption of the parameters at 120 mins contact time for both particle size is thus; Nitrate (79.49-89.69),COD (42.86-80.36),BOD (51.85-96.30),DO (34.67-74.67),Cl − (58.61-88.84),TSS (95.14-97.60),TDS (98.34-99.93),and EC (87.92-91.46).
From Table 3, at 60 mins contact time, carbonized

Table 1 :
Use of carbonized/uncarbonized waste protein sorbents in removal of pollutants from wastewater.
Value in parenthesis is pH result before treatment.

Table 2 :
Use of carbonized/uncarbonized waste cellulosic sorbents in removal of pollutants from wastewater.

Table 3 :
Use of carbonized/uncarbonized waste protein sorbents in removal of heavy metals from wastewater.

Table 4 :
Use of carbonized/uncarbonized waste cellulosic sorbents in removal of heavy metals from wastewater.