There might be a chemical reaction called chemical adsorption. The adsorption is actually a physicochemical process.

Adsorption can be either physical or chemical, depending on the forces/interactions of adsorbate and adsorbent. Physical adsorption is dominated by van der Waals force while chemisorption involves the formation of new, ionic or covalent bonds. Yet there is a chemical reaction occurring (i.e., if the mode of adsorption is chemisoprtion). For example, during ligand exchange processes.

In many cases the adsorption is physical phenomenon where adsorbate adsorb on the adsorbent surface by vander waals forces and forms very weak bond and regeneration is very easy in such cases. Whereas, i have observed physical and chemical phenomenon occurring simultaneously in adsorption of fluoride on treated alumina surface. Identification of type of adsorption can be done by isotherm analysis if both freundlich and Langmuir fitted well for your process then it can be said that the adsorption is neither physical nor chemical but the combination of both. However, chemical adsorption is dominated when adsorbent is prepared by chemical activation and formation  and presence of various chemical compounds during adsorption process  can also be confirmed by XRD pattern if it is compared with standard JCPDS library data card. If your targeted elements is found to form some compounds and its presence on the surface after adsorption then can be concluded that it is chemisorption.

Adsorption is generally classified as a physical treatment, but more specifically can be called a "physicochemical" treatment. The chemical part is represented by the bonds between the adsorbent and the pollutant. 

Actually, the adsorption process, in general, it is physically process due to the most of adsorbed molecules occured on the surface of adsorbent (has porous structure), and in the same time, some chemical attraction forces maybe obtained on the active sites such as acidic groups on the surface..  

There are two types of adsorption:physical adsorption and chemical adsorption.The first one happen when the molecules aggregate on the surface of the adsorbent without any reaction while the second one happen with the chemical reaction.

Adsorption is a physico-chemical phenomenon, as above menthioned, it can be physical (reversible) or chemical (irreversible) in nature of forces and bonds between surface and molecules being adsorbed. Also, some intermediate cases are possible. Adsorption phenomena may be applied for treatment of your material in order to reach the desired material properties. Adsorption alsways occurrs by the contact of at least two phases.

Adsorption, as a method of water treatment, is purely a physical method since it does not involved addition of chemicals to the waste water to be treated. But the mechanism of adsorption process could be physical or chemical depending on the nature of forces binding the pollutant to the surface of the adsorbent used. If the forces are weak van der Waals' then it is physical. if the binding forces are strong chemical bonding then the mechanism is chemical 

If the adsorbate gets trapped in the holes and cracks of adsorbent or if it gets held on the surface by weak vanderwaal's forces, then it may be termed physisorption. However, if chemical bonds, complexes, chelates... are formed, leading to the formation of a new compound on the surface, then it can be termed chemisorption.   In general both physisorption and chemisorption occur during adsorption, though the predominance of one may be high. Some tools can be used to discern between these two. 1). If desorption is more using distilled water alone, it can be physisorption. 2). If desorption is more by use of any eluent, it could be chemisorption. 3). If the rate of reaction follows Pseudo second order model, it could be chemisorption. 4). If new crystals are observed after adsorption through XRD, then it is chemisorption. 5). Using FTIR we can know, if it is physi or chemi sorption. 6). SEM images could give an insight into the process. 7). If, there is not much influence of variation in pH is observed in sorption, then it could be physisorption. 8). If the rate of sorption is very rapid in the initial few minutes of sorpion, then chemisorption might be involved. 9). Fitting the data to Dubinin-Radushkevich isotherm model and by calculating the value of (E), we can know, if it is physi or chemi sorption. 10). Using Elovich's kinetic model, we can know, if it is physi or chemi sorption . 11). EDAX and XPS studies would give valuable insights to know, if it is physi or chemi sorption. 12). Intraparticle diffusion analysis and the shape of line (obtained from graph) helps us to know if  it is physi or chemi sorption 

Adsorption will be physical treatment.  See definitions given below:-

"the process by which an ultrathin layer of one substance forms on the surface of another substance."

"object] (Of a solid) hold (molecules of a gas or liquid or solute) as a thin film on the outside surface or on internal surfaces within the material: the dye is adsorbed on to the fibre."

From the definitions alone one would conclude that it is more a physical phenomenon.

http://www.thefreedictionary.com/adsorption

http://www.oxforddictionaries.com/definition/english/adsorb

Adsorption method of treating wastewater at best can be classified as a physicochemical water treatment method (A combination of both physisorption and Chermisorption). Depending on the type of mechanism that proceeds between the surface of the adsorbent and the adsorbate, it could either be described as a chemical or physical process. In most cases, the adsorbent to be used undergoes some pre-treatment or modification methods using metals, acids, bases, surfactants, or heating. during some of these processes especially where chemical grafting is applied, then the whole process becomes purely a chemical process right from the onset. On the contrary, where no modification is done and the mechanism involves only a week van der Waals' forces then the physisorption process is always responsible. In such an instance, we can say that the process is a physical method.@ Mohamed Gar Alalm.